PATENT DOCUMENT

Publication Number: US-8094161-B2
Application Number: US-94194710-A
Country: US
Kind Code: B2

Title: Virtualization of graphics resources

Abstract:
Graphics resources are virtualized through an interlace between graphics hardware and graphics clients. The interface allocates the graphics resources across multiple graphics clients, processes commands for access to the graphics resources from the graphics clients, and resolves conflicts for the graphics resources among the clients.

Claims:
1. A method of virtualizing graphics resources comprising:
 allocating, by a data processing system, a graphics resource to a plurality of graphics clients, wherein the graphics resource comprises graphics hardware; 
 
       assigning a first identifier to reference the graphics resource in a command;
 sending the first identifier to the graphics client that requested allocation of the graphics resource; 
 associating the first identifier with an entry in a virtualization map containing information about the allocation of the graphics resource; 
 processing commands for access to the graphics resource from the plurality of graphics clients, wherein processing commands comprises: 
 locating the commands in a command stream; 
 replacing the first identifier in the commands with a second identifier for the graphics resource, wherein the first identifier is different than the second identifier; and 
 resolving a conflict for the graphics resource among the plurality of graphics clients. 
 
     
     
       2. The method of  claim 1 , wherein locating the commands comprises:
 jumping to the commands using offset values specified in a series of jump packets in the command stream. 
 
     
     
       3. The method of  claim 1 , wherein resolving a conflict comprises:
 determining the graphics resource has been used by a second graphics client when a first graphics client requests access to the graphics resource; and 
 refreshing the graphics resource with data for the first graphics client. 
 
     
     
       4. The method of  claim 3 , wherein refreshing the graphics resource comprises:
 paging data in the graphics resource for the second graphics client into a backing store; and 
 paging the data for the first graphics client from the backing store into the graphics resource. 
 
     
     
       5. The method of  claim 3 , wherein refreshing the graphics resource comprises:
 paging the data for the first graphics client from a backing store into a like graphics resource; and 
 assigning the like graphics resource an identifier that was previously assigned to the graphics resource. 
 
     
     
       6. The method of  claim 1 , wherein processing commands comprises:
 inserting a reference to a graphics hardware semaphore before a command that causes the conflict for the graphics resource; and 
 clearing the graphics hardware semaphore when the conflict is resolved. 
 
     
     
       7. The method of  claim 1  further comprising:
 creating a command requesting access to the graphics resource. 
 
     
     
       8. The method of  claim 7 , wherein creating a command comprises:
 inserting a jump packet to a next command containing an identifier. 
 
     
     
       9. A non-transitory machine-readable storage medium storing executable instructions to cause a processing system to perform a method comprising:
 allocating a graphics resource to a plurality of graphics clients, wherein the graphics resource comprises graphics hardware; 
 assigning an identifier to reference the graphics resource in a command; 
 sending the identifier to the graphics client that requested allocation of the graphics resource; 
 associating the identifier with an entry in a virtualization map containing information about the allocation of the graphics resource; 
 processing commands for access to the graphics resource from the plurality of graphics clients, wherein processing commands comprises: 
 locating the commands in a command stream; and 
 replacing the identifier in the commands with an address for the graphics resource, wherein the identifier is different than the address. 
 
     
     
       10. The non-transitory machine-readable storage medium of  claim 9 , wherein locating the commands comprises:
 jumping to the commands using offset values specified in a series of jump packets in the command stream. 
 
     
     
       11. The non-transitory machine-readable storage medium of  claim 9 , wherein the method comprises resolving a conflict for the graphic resource among the plurality of graphics clients and wherein resolving the conflict comprises:
 determining the graphics resource has been used by a second graphics client when a first graphics client requests access to the graphics resource; and 
 refreshing the graphics resource with data for the first graphics client. 
 
     
     
       12. The non-transitory machine-readable storage medium of  claim 11 , wherein refreshing the graphics resource comprises:
 paging data in the graphics resource for the second graphics client into a backing store; and 
 paging the data for the first graphics client from the backing store into the graphics resource. 
 
     
     
       13. The non-transitory machine-readable storage medium of  claim 11 , wherein refreshing the graphics resource comprises:
 paging the data for the first graphics client from a backing store into a like graphics resource; and 
 assigning the like graphics resource an identifier that was previously assigned to the graphics resource. 
 
     
     
       14. The non-transitory machine-readable storage medium of  claim 9 , wherein processing commands comprises:
 inserting a reference to a graphics hardware semaphore before a command that causes a conflict for the graphics resource; and 
 clearing the graphics hardware semaphore when the conflict is resolved. 
 
     
     
       15. The non-transitory machine-readable storage medium of  claim 9  further comprising:
 creating a command requesting access to the graphics resource using the identifier. 
 
     
     
       16. The non-transitory machine-readable storage medium of  claim 15 , wherein creating a command comprises:
 inserting a jump packet to a next command containing an identifier. 
 
     
     
       17. A computer system comprising:
 a processor coupled to a memory through a bus; 
 a graphics processor coupled to the processor through the bus and associated with graphics resources; and 
 a driver executed by the graphics processor to cause the graphics processor to allocate a graphics resource to a plurality of graphics clients, wherein the graphics resource comprises graphics hardware, 
 assign an identifier to reference the graphics resource in a command, 
 send the identifier to the graphics client that requested allocation of the graphics resource, 
 associate the identifier with an entry in a virtualization map containing information about the allocation of the graphics resource, 
 process commands for access to the graphics resource from the plurality of graphics clients, wherein the driver, when processing commands, further causes the graphics processor to: 
 locate the commands in a command stream, 
 replace the identifier in the commands with an address for the graphics resource, 
 
       wherein the identifier is different than the address, and
 resolve a conflict for the graphics resource among the plurality of graphics clients. 
 
     
     
       18. The computer system of  claim 17 , wherein the driver, when locating the commands, further causes the graphics processor to jump to the commands using offset values specified in a series of jump packets in the command stream. 
     
     
       19. The computer system of  claim 17 , wherein the driver, when resolving a conflict, further causes the graphics processor to
 determine the graphics resource has been used by a second graphics client when a first graphics client requests access to the graphics resource, and 
 refresh the graphics resource with data for the first graphics client. 
 
     
     
       20. The computer system of  claim 19 , wherein the driver, when refreshing the graphics resource, further causes the graphics processor to
 page data in the graphics resource for the second graphics client into a backing store, and 
 page the data for the first graphics client from the backing store into the graphics resource. 
 
     
     
       21. The computer system of  claim 19 , wherein the driver, when refreshing the graphics resource, further causes the graphics processor to
 page the data for the first graphics client from a backing store into a like graphics resource, and 
 assign the like graphics resource an identifier that was previously assigned to the graphics resource. 
 
     
     
       22. The computer system of  claim 17 , wherein the driver, when processing commands, further causes the graphics processor to
 insert a reference to a graphics hardware semaphore before a command that causes the conflict for the graphics resource, and 
 clear the graphics hardware semaphore when the conflict is resolved. 
 
     
     
       23. The computer system of  claim 17  further comprising:
 a client driver executed by the processor from the memory to cause the processor to create a command requesting access to the graphics resource using the identifier. 
 
     
     
       24. The computer system of  claim 23 , wherein the client driver further causes the processor to insert a jump packet to a next command containing an identifier when creating a command. 
     
     
       25. A data processing system comprising:
 means for allocating, by a hardware device, a graphics resource to a plurality of graphics clients, wherein the graphics resource comprises graphics hardware; 
 means for assigning an identifier to reference the graphics resource in a command; 
 means for sending the identifier to the graphics client that requested allocation of the graphics resource; 
 means for associating the identifier with an entry in a virtualization map containing information about the allocation of the graphics resource; 
 means for processing commands for access to the graphics resource from the plurality of graphics clients, wherein the means for processing commands comprises: 
 means for locating the commands in a command stream; and 
 means for replacing the identifier in the commands with an address for the graphics resource, wherein the identifier is different than the address.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/643,425, filed on Dec. 20, 2006 now U.S. Pat. No. 7,830,395, which is a continuation of U.S. patent application Ser. No. 10/964,220, filed on Oct. 12, 2004 now U.S. Pat. No. 7,834,882, which is a divisional application of U.S. patent application Ser. No. 10/043,018, filed on Jan. 8, 2002, now issued as U.S. Pat. No. 6,809,736. The present application is also related to U.S. patent application Ser. No. 10/042,882 and Ser. No. 10/042,901, both filed on Jan. 8, 2002 and assigned to the same assignee as the present application. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to computer graphics, and more particularly to virtualizing resources for computer graphics. 
     COPYRIGHT NOTICE/PERMISSION 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to the software and data as described below and in the drawings hereto: Copyright© 1999-2002, Apple Computer, Inc., All Rights Reserved. 
     BACKGROUND OF THE INVENTION 
     A graphics kernel driver typically interfaces between graphics client drivers and graphics hardware to assign graphics resources to each client driver and to administer the submission of graphics commands to the graphics hardware. Each client driver has explicit knowledge of the graphics resources it is assigned and references the resources in its commands using the physical address of the resources. As more sophisticated graphics features are developed, the demand for graphics resources is ever increasing but the graphics resources are limited by the graphics hardware and other system constraints. The assigned resources cannot be shared among clients because the graphics hardware is not designed to handle resource contention among the clients. Additionally, the client drivers are required to manage their own internal resource conflicts. For example, they must handle their attempts to use more than available graphics memory. 
     SUMMARY OF THE INVENTION 
     Graphics resources are virtualized through an interface between graphics hardware and graphics clients. The interface allocates the graphics resources across multiple graphics clients, processes commands for access to the graphics resources from the graphics clients, and resolves conflicts for the graphics resources among the clients. 
     In one aspect, the interface is a graphics kernel that assigns an identifier to a resource when allocated by a graphics client and the client uses the identifier instead of an address for the resources when requesting access to the resource. 
     Because the native command structure for the graphics hardware is unaffected by the virtualization, neither the applications nor the hardware require modification to operate in conjunction with the present invention. Furthermore, because the virtualized resources appear as unlimited resources to the graphics clients, the clients can be simplified since, for example, they are no longer required to de-fragment or compact their assigned resources. 
     The present invention describes systems, methods, and machine-readable media of varying scope. In addition to the aspects of the present invention described in this summary, further aspects of the invention will become apparent by reference to the drawings and by reading the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a diagram illustrating a graphics driver stack that incorporates the present invention; 
         FIG. 1B  is a diagram illustrating a system overview of one embodiment of processing in the driver stack of  FIG. 1A ; 
         FIGS. 2A-B  illustrate graphics command streams according to one embodiment of the invention; 
         FIG. 3A-C  illustrate processing of command buffers according to embodiments of the invention; 
         FIG. 4A  is a flowchart of a graphics client driver method to be performed by a computer processor according to an embodiment of the invention; 
         FIG. 4B  is a flowchart of a graphics kernel driver method to be performed by a graphics processor according to an embodiment of the invention; 
         FIG. 5A  is a diagram of one embodiment of an operating environment suitable for practicing the present invention; and 
         FIG. 5B  is a diagram of one embodiment of a computer system suitable for use in the operating environment of  FIG. 5A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description of embodiments of the invention, reference is made to the accompanying drawings in which like references indicate similar elements, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical, functional, and other changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
     In one embodiment, the present invention is integrated into a graphics driver stack  100  as illustrated in  FIG. 1A . A graphics kernel driver  101  interfaces between graphics client drivers  103 ,  105 ,  107 ,  109  and graphics hardware  111  to virtualize limited graphics resources used by the graphics hardware  111  and manage contention among the client drivers for the resources. The virtualized resources appear as unlimited resources to the client drivers, which allows the client drivers to be simplified since, for example, they are no longer required to de-fragment or compact their assigned memory. 
     Graphics resources eligible for virtualization include any limited resource used by the graphics hardware  111 , such as graphics memory, either integrated in the graphics hardware  111  or allocated in system memory, GART (graphics address re-mapping table) entries, memory apertures for accessing video memory or registers, specialized memory areas for hierarchical depth buffers, among others. For the sake of clarity, the virtualization of graphics memory is used as an example throughout, but the invention is not so limited. 
     Referring now to an exemplary embodiment shown in  FIG. 1B , the kernel driver  101  manages the allocation of memory among clients through a virtualization map  117 , such as a range allocation table. The virtualization map  117  indicates how graphics memory is currently allocated, including which block a client is using. 
     An application  115  calls an OpenGL engine  113  through an OpenGL API (application program interface)  119  to create an image. The OpenGL engine  113 , executing on the central processing unit (CPU) of the computer, determines how to divide the image processing work between the CPU and the graphics processor of the graphics hardware  111 , and sends the commands to be processed by the graphics processor to the OpenGL client driver  103  through a client driver API  121 . The client driver  103 , also executing on the CPU, evaluates the commands and determines that it needs graphics memory to create the image. The client driver  103  requests a block of memory from the kernel driver  101  through a kernel driver API call  123 . The kernel driver  101 , executing on the graphics processor, records the request in an entry in the virtualization map  117 , and associates an identifier with the entry. The kernel driver  101  returns the identifier to the client driver  103  for use in all commands that access the memory block. Because the native command structure for OpenGL and the graphics hardware is unaffected by the virtualization, neither the application  115 , the OpenGL engine  113 , nor the hardware  111  require modification to operate in conjunction with the present invention. 
     In one embodiment, the kernel driver  101  performs the actual physical allocation of memory when the client driver  103  submits a command that references the identifier. In another embodiment, the kernel driver  101  physically allocates the memory upon receiving the allocation request. In either case, when all physical memory is already allocated, the kernel driver  101  pages a corresponding amount of data currently in memory to a backing store and updates the virtualization map  117 . The kernel driver  101  uses the virtualization map  117  to determine how to page the data back into memory for subsequent processing. Details of the paging are described further below in conjunction with  FIG. 4B . 
     In one embodiment, the identifier is a “token” that represents the memory block and the client driver  103  creates tokenized commands by substituting the token for the memory address. When the client driver  103  submits a tokenized command to the graphics hardware  111 , the kernel driver  101  extracts the token, finds the address of the memory block represented by the token in the virtualization map  117 , and replaces the token with the real address. When the tokenized commands are submitted as part of a standard graphics command stream, the kernel driver  101  must parse the stream into its individual commands and evaluate most, if not all, the commands to determine which contain tokens. This can be a slow and expensive operation. 
     Therefore, in another embodiment, the client driver  103  formats the command stream as illustrated in  FIG. 2B . A command stream  200  contains standard commands  203 ,  205 , followed by a tokenized command  207 , followed by various other commands, and terminates with a tokenized command  209 . The stream  200  is prefaced with a “jump” packet  201  that points to the first tokenized command  207  in the stream  200 . The tokenized command  207  contains another jump packet that points to the next tokenized command in the stream  200 , and so on until the last jump packet in the stream is reached. The jump packets thus create a linked list of tokenized commands, allowing the kernel driver  101  to ignore the standard commands in the stream  200  without having to evaluate each command and individually. 
     In one embodiment, the jump packets contain a packet type and an offset value relative to the current packet. Assuming a command stream  210  as illustrated in  FIG. 2B , the kernel driver  101  reads the first command in the stream, which is a “start” jump packet  211 . The kernel driver  101  extracts the offset value from the start jump packet  211  and deletes the packet from the stream. The kernel driver  101  uses the offset value to jump to the next jump packet  219 , which is in the “load texture” command  217 . The kernel driver  101  extracts the next offset value and packet type from the jump packet  219 . The packet type identifies the packet  219  as a “texture” packet, indicating that the token  221  represents a block of memory containing texture data. The kernel driver  101  replaces the tokenized command  217  with a valid graphics command  225  containing the memory address  223  corresponding to the token  221 , and jumps to the jump packet in the next tokenized command in the stream. The resulting stream  220  received by the graphics hardware  111  contains “polygon”  213  and “change state”  215  commands unchanged from the stream  210  submitted by the client driver  103 , and a “load texture” command  225  as modified by the kernel driver  101 . Thus, the final processing of the command stream by the kernel driver only requires each jump packet to be read and written to and from memory while the majority of the command data generated by the client driver is not read or interpreted by the kernel driver. 
     Alternate embodiments in which the jump packets are not embedded in the tokenized commands in the stream or are submitted as a separate stream associated with the command stream are contemplated as within the scope of the invention. 
     When a particular region of graphics memory requested by a current client driver has been reused by a previous client driver, the kernel driver completes the use of the memory by the previous client driver, and prepares the resource for use by the current client driver. When the kernel driver processes a tokenized command, the graphics memory referenced by the token may be in one of two states: valid for immediate use by the client driver or not. If the memory is valid for immediate use, the kernel driver proceeds as previously described. If the memory is not valid for immediate use, the kernel driver refreshes the current client&#39;s data by allocating a new region of graphics memory and page the data into it. Before doing this however, the kernel driver submits all graphics commands in the current client&#39;s command stream up to the current jump packet to the graphics hardware before it starts allocating the new region of graphics memory for the current client because the process of allocation might result in the deallocation and paging of graphics memory previously referenced in the current command stream. Details of the refreshing of data are described further below in conjunction with  FIG. 4B . 
     Command buffers are commonly used to hold the command streams from multiple clients. As shown in  FIG. 3A , as the client driver generates commands, the CPU fills the appropriate buffer  301 ,  303 . When a buffer is full, it is placed in a processing queue for the graphics hardware, and the CPU assigns another buffer to the client driver. It will be appreciated that when jump packets are used, the client driver loads the start jump packet first in the buffer. 
     The command buffers allow multiple clients to create streams asynchronously to each other. The command buffers also allow the graphics hardware and the CPU to operate asynchronously, keeping both busy even though they typically operate at different speeds. 
     In one embodiment, the queued buffers are a arranged as a linked list as shown in  FIG. 3B . The contents of the buffers  301 ,  303 ,  305  are read by the graphics hardware  111  as a linear stream of commands for execution in a serialized fashion, i.e., all the commands in one buffer are executed before the commands in the next buffer in the queue. The serialized, linear execution by the graphics hardware  111  provides the kernel driver  101  with an memory management timeline to follow in processing the commands that reference graphics memory. After processing by the kernel driver, the entire command stream is valid for consumption by the graphics hardware since the conflicts between clients due to reuse of memory have been resolved and the jump packets and tokenized commands have been replaced with valid graphics hardware commands. 
     In an alternate embodiment, the identifier for the memory block allocated to the client driver  103  is the physical address of the memory. Because the client expects memory address to be unchanged until it de-allocates the memory, the kernel driver  101  employs special graphics hardware features to manage the virtualization of memory. In one embodiment, the kernel driver  101  uses graphics semaphores that cause the graphics hardware to suspend processing of one buffer and switch to processing another buffer, thus interleaving the processing of the command buffers from different clients, and creating multiple inter-dependent linear timelines as illustrated in  FIG. 3C . 
     For example, assume client A places a command in buffer  307  that references memory also used by client C. When the kernel driver  101  reaches that command in buffer  307 , it inserts a reference to semaphore  313  before the command, effectively dividing the buffer  307  into command sequences  311 ,  315 . The graphics hardware  111  processes command sequence  311  in buffer  307  until it reaches semaphore  313 , which directs it to switch to processing the next queued buffer  309 . While the graphics hardware  111  is processing buffer  309 , the kernel driver  101  pages the appropriate data back in and clears the semaphore  313 . 
     Similarly, assume client B places a command in buffer  309  that references memory also used by client D, so the kernel driver  101  inserts a reference to semaphore  321  in buffer  309 , creating command sequences  319 ,  323 . When the graphics hardware  111  reaches semaphore  321 , it determines that semaphore  313  is clear and resumes processing buffer  307  at command sequence  315 . Because the kernel driver  101  has cleared semaphore  321  by the time the graphics hardware finishes processing command sequence  315 , the graphics hardware can now process command sequence  323 . 
     Next, the particular methods of the invention are described in terms of computer software with reference to a series of flowcharts. The methods to be performed by a processing system constitute computer programs made up of executable instructions illustrated as blocks (acts). Describing the methods by reference to a flowchart enables one skilled in the art to develop such programs including such instructions to carry out the methods on suitably configured hardware (the processing unit of the hardware executing the instructions from machine-readable media). The executable instructions may be written in a computer programming language or may be embodied in firmware logic. If written in a programming language conforming to a recognized standard, such instructions can be executed on a variety of hardware platforms and interface to a variety of operating systems. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. Furthermore, it is common in the art to speak of software, in one form or another (e.g., program, procedure, process, application, module, logic . . . ), as taking an action or causing a result. Such expressions are merely a shorthand way of saying that execution of the software by a machine causes the processor of the machine to perform an action or produce a result. It will be further appreciated that more or fewer processes may be incorporated into the methods illustrated in  FIGS. 4A-B  without departing from the scope of the invention and that no particular order is implied by the arrangement of blocks shown and described herein. 
     Referring first to  FIG. 4A , the acts to be performed by a computer processor executing a client driver method  400  that tokenizes commands are shown. The client driver method  400  receives an image command (block  401 ) and determines if graphics resources are required to process the command (block  403 ). If the necessary resources have not been previously allocated, the method  400  requests the resources from the kernel driver (block  405 ) and receives a token in return (block  407 ). The method  400  creates the graphics commands to perform the image command at block  409 . The processing represented by block  409  includes creating the jump packets with the appropriate offsets and packet types, and inserting the jump packets and tokens in the commands. The particular packet types used by embodiments of the invention are dictated by the command set of the underlying graphics hardware. One exemplary set of packet types, called “op codes,” for graphics memory are shown in Table 1. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Op Code 
                 Remarks 
               
               
                   
               
             
            
               
                 kGLStreamStart 
                 Start the stream 
               
               
                 kGLStreamEnd 
                 Terminate the stream 
               
               
                 kGLStreamCopyColor 
                 Copy an image between two draw buffers 
               
               
                 kGLStreamCopyColorScale 
                 Copy an image between two draw buffers 
               
               
                   
                 with scaling 
               
               
                 kGLStreamDrawColor 
                 Draw an image to the current draw buffer 
               
               
                 kGLStreamTexture0 
                 Set the current texture object on texture 
               
               
                   
                 unit zero 
               
               
                 kGLStreamTexture1 
                 Set the current texture object on texture 
               
               
                   
                 unit one 
               
               
                 kGLStreamTexture2 
                 Set the current texture object on texture 
               
               
                   
                 unit two 
               
               
                 kGLStreamTexture3 
                 Set the current texture object on texture 
               
               
                   
                 unit three 
               
               
                 kGLStreamNoTex0 
                 Remove any texture from texture unit zero 
               
               
                 kGLStreamNoTex1 
                 Remove any texture from texture unit one 
               
               
                 kGLStreamNoTex2 
                 Remove any texture from texture unit two 
               
               
                 kGLStreamNoTex3 
                 Remove any texture from texture unit three 
               
               
                 kGLStreamVertexBuffer 
                 Set the current vertex object 
               
               
                 kGLStreamNoVertexBuffer 
                 Remove any current vertex object 
               
               
                   
               
            
           
         
       
     
     If there is no existing command buffer (block  411 ), the method  400  starts a new buffer (block  413 ) and inserts a start jump packet at the beginning of the buffer (block  415 ) with an offset to the first tokenized command in the buffer. Each graphics command is loaded in the buffer (block  417 ) until all graphics commands are buffered (block  419 ) or the current buffer is full (block  421 ). If the current buffer is full and more commands need to be buffered, the method  400  returns to block  413  to start a new buffer. 
     Referring now to  FIG. 4B , the acts to be performed by a graphics processor executing a kernel driver method  430  corresponding to the client driver method  400  are shown. The kernel driver method  430  is illustrated as two parallel processing threads, one that interfaces with the client driver (starting at block  431 ) and one that interfaces with the graphics hardware (starting at block  451 ). It will be appreciated that the invention is not limited to such parallel processing implementations. 
     When the method  430  receives an allocation request from a client driver (block  431 ), it determines if the requested amount of resource is available (block  433 ). If not, the method  430  pages out a sufficient amount of data belonging to another client (block  435 ). The method  430  allocates the resource, including assigning a token and updating its memory management information, such as the virtualization map  117  illustrated in  FIG. 1B . The token is returned to the requesting client driver at block  439 . The client driver method  430  waits until another request is received (block  441 ) and returns to block  431  to process the new request. 
     When the client driver submits a buffer of commands to the graphics hardware for processing, the kernel driver method  430  extracts the offset and type from the next jump packet in the buffer (block  451 ). If the next jump packet is the first jump packet, i.e., a start jump packet (block  453 ), the method  430  deletes the start jump packet from the buffer (block  461 ) and jumps to the jump packet defined by the offset (block  465 ) to continue processing. Otherwise, the method  430  uses the jump packet type to locate the token in the command and determines if the resource corresponding to the token has been reused (block  455 ). If so, the kernel driver method  430  refreshes the data required by the current command (block  457 ). Because of the abstraction provided by the token, the kernel driver can page the data into a different available graphics resource or page out the data currently in the original resource and page in the data required by the current command. The token is replaced with the address of the resource (block  459 ) and the jump packet is deleted (block  461 ). If the current jump packet is the last in the buffer (block  463 ), the method  430  waits for another buffer (block  467 ) and returns to block  451  to process the new buffer. Otherwise, the next jump packet in the buffer is processed. 
     In an alternate embodiment, the processing represented by block  437  is a logical allocation of the resource to the client driver and the processing represented by blocks  433  through  435  is not performed. The kernel driver method  430  performs the physical allocation, and any necessary paging, when it encounters the first tokenized command that references the resource in the command buffer. 
     In one embodiment, the kernel driver method  430  uses system memory as its backing store for data that must be paged out of the virtualized graphics resources. The method  430  can request the CPU read the data into system memory, or it can request the graphics hardware to write the data to the system memory. The latter operation can be performed asynchronously with the CPU, but not all graphics hardware may be able to perform the operation or there may be incompatibilities between the graphics hardware and the CPU. When the operating system virtualizes system memory, the operating system may further page the data to mass storage. It will be appreciated that once the data has been written to system memory, a virtual memory operating system may further page the data to mass storage. 
     In one embodiment, what data to page into system memory is determined by various paging criteria, such as type of graphics resource, priority, and paging algorithm. Some resources, like graphics memory, are very expensive to page because the data contained in the graphics memory often must be copied into system memory. The priorities may be allocated within graphics resources types. For example, texture objects generally have a lower priority than frame buffers when paging graphics memory. Other resources, like GART entries may be paged inexpensively because the paging only requires the modification of the GART table, i.e., no data is actually relocated. Because the relative cost of paging different types of resources is quite different, different paging algorithms are used for each. 
     For example, when a client driver requests an allocation of graphics memory but there is not enough free contiguous memory to service the request, all graphics memory resources owned by all clients are candidates for paging. The first resources selected are owned by other clients because there may be an arbitrarily long period of time before the other clients are run again. When considering graphics memory owned by the requesting client driver, the kernel driver uses an algorithm that dynamically switches from LRU (least recently used) to MRU (most recently used) based on whether or not the client driver is overcommitted in its texture usage. An overcommitted application is an application that uses more texture memory in rendering a single frame than can be supplied by the graphics hardware. When a client driver that is not overcommitted runs out of graphics memory it is because some user input has caused the client driver to render a new scene so the LRU algorithm is used, based on the assumption that the least recently used memory resources may never be used again. When a client driver that is overcommitted runs out of graphics memory this means that it will do so cyclically every frame, so the MRU algorithm is chosen because an LRU algorithm would result in every memory resource owned by the client driver being paged one or more times per frame. 
     GART entry paging is managed differently because the cost of changing GART entries is essentially unrelated to the size of the memory resource. The first candidates for paging are GART entries that may never be used again. For example, graphics memory texture objects each have a GART entry that was used to transfer the texture from system memory to graphics memory. Once the texture has been moved to graphics memory, the GART entry will never be used again unless the texture is paged from graphics memory and then reloaded. Therefore, it is likely that choosing such a GART entry for paging will have no performance cost. The remaining GART entries are categorized from highest to lowest priority for paging, with the lowest priority assigned to the CART entry for each client&#39;s command buffer, which must be mapped into CART for the client driver to use the graphics hardware at all. 
     One of skill in the art will appreciate that other types of graphics resources may have different algorithms for selecting which resources are candidates for paging that allow the resources to be transparently managed with respect to multiple clients as described above for graphics memory and CART. 
     In one embodiment, the kernel driver method  430  uses a collection of data objects, each of which represents an allocated resource, as a virtualization map. The tokens identify the data objects within the virtualization map. Each data object contains the address range for the corresponding resource. When the data in the resource is paged out, a “dirty” flag is set and a pointer to the backing store holding the data is stored in the object. It will be appreciated that the layer of abstraction between the client and the physical resources provided by the token allows the data to be paged into a resource address different than it previously occupied without the client driver being aware of the change. 
     The following description of  FIGS. 5A-B  is intended to provide an overview of computer hardware and other operating components suitable for performing the methods of the invention described above, but is not intended to limit the applicable environments. One of skill in the art will immediately appreciate that the invention can be practiced with other processing system configurations, including hand-held devices, multiprocessor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, and the like. The invention can also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. 
       FIG. 5A  shows several computer systems that are coupled together through a network  3 , such as the Internet. The term “Internet” as used herein refers to a network of networks which uses certain protocols, such as the TCP/IP protocol, and possibly other protocols such as, for example, the hypertext transfer protocol (HTTP) or hypertext markup language (HTML) documents that make up the World Wide Web (web). The physical connections of the Internet and the protocols and communication procedures of the Internet are well known to those of skill in the art. Access to the Internet  3  is typically provided by Internet service providers (ISP), such as the ISPs  5  and  7 . Users on client systems, such as client computer systems  21 ,  25 ,  35 , and  37  obtain access to the Internet through the Internet service providers, such as ISPs  5  and  7 . Access to the Internet allows users of the client computer systems to exchange information, receive and send e-mails, and view documents, such as documents which have been prepared in the HTML format. These documents are often provided by web servers, such as web server  9  which is considered to be “on” the Internet. Often these web servers are provided by the ISPs, such as ISP  5 , although a compute system can be set up and connected to the Internet without that system being also an ISP as is well known in the art. 
     The web server  9  is typically at least one computer system which operates as a server compute system and is configured to operate with the protocols of the World Wide Web and is coupled to the Internet. Optionally, the web server  9  can be part of an ISP which provides access to the Internet for client systems. The web server  9  is shown coupled to the server computer system  11  which itself is coupled to web content  10 , which can be considered a form of a media database. It will be appreciated that while two computer systems  9  and  11  are shown in  FIG. 5A , the web server system  9  and the server computer system  11  can be one computer system having different software components providing the web server functionality and the server functionality provided by the server computer system  11  which will be described further below. 
     Client computer systems  21 ,  25 ,  35 , and  37  can each, with the appropriate web browsing software, view HTML pages provided by the web server  9 . The ISP  5  provides Internet connectivity to the client computer system  21  through the modem interface  23  which can be considered part of the client computer system  21 . The client computer system can be a personal computer system, a network computer, a Web TV system, or other such computer system. Similarly, the ISP  7  provides Internet connectivity for client systems  25 ,  35 , and  37 , although as shown in  FIG. 5A , the connections are not the same for these three computer systems. Client computer system  25  is coupled through a modem interface  27  while client computer systems  35  and  37  are part of a LAN. While  FIG. 5A  shows the interfaces  23  and  27  as generically as a “modem,” it will be appreciated that each of these interfaces can be an analog modem, ISDN modem, cable modem, satellite transmission interface (e.g. “Direct PC”), or other interfaces for coupling a computer system to other computer systems. Client computer systems  35  and  37  are coupled to a LAN  33  through network interfaces  39  and  41 , which can be Ethernet network or other network interfaces. The LAN  33  is also coupled to a gateway computer system  31  which can provide firewall and other Internet related services for the local area network. This gateway computer system  31  is coupled to the ISP  7  to provide Internet connectivity to the client computer systems  35  and  37 . The gateway computer system  31  can be a conventional server computer system. Also, the web server system  9  can be a conventional server computer system. 
     Alternatively, as well-known, a server computer system  43  can be directly coupled to the LAN  33  through a network interface  45  to provide files  47  and other services to the clients  35 ,  37 , without the need to connect to the Internet through the gateway system  31 . 
       FIG. 5B  shows one example of a conventional computer system that can be used as a client computer system or a server computer system or as a web server system also be appreciated that such a computer system can be used to perform many of the functions of an Internet service provider, such as ISP  5 . The computer system  51  interfaces to external systems through the modem or network interface  53 . It will be appreciated that the modem or network interface  53  can be considered to be part of the computer system  51 . This interface  53  can be an analog modem, ISDN modem, cable modem, token ring interface, satellite transmission interface (e.g. “Direct PC”), or other interfaces for coupling a computer system to other computer systems. The computer system  51  includes a processing unit  55 , which can be a conventional microprocessor such as an Intel Pentium microprocessor or Motorola Power PC microprocessor. Memory  59  is coupled to the processor  55  by a bus  57 . Memory  59  can be dynamic random access memory (DRAM) and can also include static RAM (SRAM). The bus  57  couples the processor  55  to the memory  59  and also to non-volatile storage  65  and to display controller  61  and to the input/output (I/O) controller  67 . The display controller  61  controls a display on a display device  63 , such as, for example, a cathode ray tube (CRT) or liquid crystal display, in accordance with the present invention. The input/output devices  69  can include a keyboard, disk drives, printers, a scanner, and other input and output devices, including a mouse or other pointing device. The display controller  61  and the I/O controller  67  can be implemented with conventional well known technology. A digital image input device  71  can be a digital camera which is coupled to an I/O controller  67  in order to allow images from the digital camera to be input into the computer system  51 . The non-volatile storage  65  is often a magnetic hard disk, an optical disk, or another form of storage for large amounts of data. Some of this data is often written, by a direct memory access process, into memory  59  during execution of software in the computer system  51 . One of skill in the art will immediately recognize that the terms “machine-readable medium” and “computer-readable medium” includes any type of storage device that is accessible by the processor  55  and also encompasses a carrier wave that encodes a data signal. 
     It will be appreciated that the computer system  51  is one example of many possible computer systems which have different architectures. For example, personal computers based on an Intel microprocessor often have multiple buses, one of which can be an input/output (I/O) bus for the peripherals and one that directly connects the processor  55  and the memory  59  (often referred to as a memory bus). The buses are connected together through bridge components that perform any necessary translation due to differing bus protocols. 
     Network computers are another type of computer system that can be used with the present invention. Network computers do not usually include a hard disk or other mass storage, and the executable programs are loaded from a network connection into the memory  59  for execution by the processor  55 . A Web TV system, which is known in the art, is also considered to be a computer system according to the present invention, but it may lack some of the features shown in  FIG. 5B , such as certain input or output devices. A typical computer system will usually include at least a processor, memory, and a bus coupling the memory to the processor. 
     It will also be appreciated that the computer system  51  is controlled by operating system software which includes a file management system, such as a disk operating system, which is part of the operating system software. One example of an operating system software with its associated file management system software is the family of operating systems known as Mac® OS from Apple Computer, Inc. of Cupertino, Calif., and their associated file management systems. The file management system is typically stored in the non-volatile storage  65  and causes the processor  55  to execute the various acts required by the operating system to input and output data and to store data in memory, including storing files on the non-volatile storage  65 . 
     Virtualization of graphics resources has been described. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the present invention. The terminology used in this application with respect to graphics is meant to include all environments that display images to a user. Therefore, it is manifestly intended that this invention be limited only by the following claims and equivalents thereof.

Metadata:
Filing Date: 20101108
Publication Date: 20120110
Grant Date: 20120110
Priority Date: 20020108
Inventors: STAUFFER JOHN
BERETTA BOB
DYKE KEN
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F15/167", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F15/167", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/001", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G5/001", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06T15/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06T15/00", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 33157972