zpios: Replace current_kernel_time() with getnstimeofday()

current_kernel_time() is not meant for performance measurement. This
should use getnstimeofday(), which is equivalent to the gethrestime()
function on Solaris.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Implement sgbufs

sgbufs use pages to store buffers. They are intended as a replacement
for slab allocation in ZIO buffers and will be proposed for inclusion
into Illumos once they are ready.

Adoption of sgbufs for buffers provides the following benefits:

1. The elimination of memory loss to SLAB fragmentation, which has been
observed to exceed 10% of system memory on some systems.

2. The ability to mmap() directly into ARC.

3. Opportunities to use page table manipulation when doing copies or
zeroes that involve page alignment.

Additional patches will be required to obtain each of these benefits.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Set zfs_arc_min to 4MB

Decrease the mimimum ARC size from 1/32 of total system memory
(or 64MB) to a much smaller 4MB.

1) Large systems with over a 1TB of memory are being deployed
   and reserving 1/32 of this memory (32GB) as the mimimum
   requirement is overkill.

2) Tiny systems like the raspberry pi may only have 256MB of
   memory in which case 64MB is far too large.

The ARC should be reclaimable if the VFS determines it needs
the memory for some other purpose.  If you want to ensure the
ARC is never completely reclaimed due to memory pressure you
may still set a larger value with zfs_arc_min.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Implement File Attribute Support

We add support for lsattr and chattr. Only attributes common to both
Solaris and Linux are supported. These are 'a', 'd' and 'i'. File
attributes exclusive to Solaris are present in the ZFS code, but cannot
be accessed or modified through this method. That was the case prior to
this patch.

This commit removes the ZFS_IOC_GETFLAGS and ZFS_IOC_SETFLAGS macros in
recognition that this is not equivalent to the Solaris operation. The
resolution of issue zfsonlinux/zfs#229 should implement something
equivalent that will permit access and modification of Solaris-specific
attributes.

This resolves a regression caused by
88c283952f0bfeab54612f9ce666601d83c4244f that broke python's
xattr.list(). This broke Gentoo Portage's FEATURES=xattr, which depended
on this.

https://bugs.gentoo.org/show_bug.cgi?id=483516
Issue zfsonlinux/zfs#1691

Original-patch-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Switch to C99

Upstream Illumos uses C99, but we have been building as C89. This
required backporting patches from Illumos from C99 to C89. There are no
known ABI compatibility issues when mixing C89 and C99 code. so lets
just build as C99 and save ourselves some trouble. This patch modifies
the autotools checks, userland code and kernel code to use C89.

Note that the Linux kernel passes -Wdeclaration-after-statement, so we
must pass -Wno-declaration-after-statement to counteract that. We also
do a little cleanup to simplify the makefiles.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Illumos #3742

3742 zfs comments need cleaner, more consistent style
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Approved by: Christopher Siden <christopher.siden@delphix.com>
Ported-by: Richard Yao <ryao@gentoo.org>

References:

https://www.illumos.org/issues/3742
illumos/illumos-gate@f7170741490edba9d1d9c697c177c887172bc741

Porting notes:

The change to zfs_vfsops.c was dropped because it involves
zfs_mount_label_policy, which does not exist in the Linux port.
Use bitfields for boolean values in znode_t

znode_t uses 1312 bytes in length on Linux 3.9.6 amd64. Switching to
bitfields for boolean values reduces the size to 1296 bytes. Further
reductions should be possible if padding were removed, but saving 16
bytes per struct can translate into megabytes of savings when hundreds
of thousands of znodes are cached. While the savings is relatively
small in comparison to memory used, the small efficiency gain is
practically free.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Remove unused option -r from zpool

Signed-off-by: Richard Yao <ryao@gentoo.org>
Implement -t option to zpool import for temporary pool names

Specifying newname to a pool import currently changes the pool name. We
implement option -t. Specifying option -t in conjuction with newpool to
zpool import will make the name change temporary. In specific, the
original pool name will be used in all label updates and therefore is
retained upon export.

This is useful in any situation where maintenance on a system's root
pool is done from another system. A good example is environments using
virtualization, where it is more desireable to do rollback of the root
dataset of a guest's root pool than it is to rollback of the zvol
hosting the guest's root pool when an issue prevents the guest from
booting properly. Other examples include maintenance on root pools
hosted on iSCSI and operating system installations on USB keys that are
used to rescue non-bootable sytems.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Add pkg-config file for libzfs

Signed-off-by: Richard Yao <ryao@gentoo.org>
fnvlist_alloc() must not be used in synctext context

fnvlist_alloc() does allocations using KM_SLEEP, which is not
permissible in the synctask context. Inline the function with a change
to use KM_PUSHPAGE as a fix.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Illumos #4045 write throttle & i/o scheduler performance work

4045 zfs write throttle & i/o scheduler performance work

1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync
read, sync write, async read, async write, and scrub/resilver.  The scheduler
issues a number of concurrent i/os from each class to the device.  Once a class
has been selected, an i/o is selected from this class using either an elevator
algorithem (async, scrub classes) or FIFO (sync classes).  The number of
concurrent async write i/os is tuned dynamically based on i/o load, to achieve
good sync i/o latency when there is not a high load of writes, and good write
throughput when there is.  See the block comment in vdev_queue.c (reproduced
below) for more details.

2. The write throttle (dsl_pool_tempreserve_space() and
txg_constrain_throughput()) is rewritten to produce much more consistent delays
when under constant load.  The new write throttle is based on the amount of
dirty data, rather than guesses about future performance of the system.  When
there is a lot of dirty data, each transaction (e.g. write() syscall) will be
delayed by the same small amount.  This eliminates the "brick wall of wait"
that the old write throttle could hit, causing all transactions to wait several
seconds until the next txg opens.  One of the keys to the new write throttle is
decrementing the amount of dirty data as i/o completes, rather than at the end
of spa_sync().  Note that the write throttle is only applied once the i/o
scheduler is issuing the maximum number of outstanding async writes.  See the
block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for
more details.

This diff has several other effects, including:

 * the commonly-tuned global variable zfs_vdev_max_pending has been removed;
use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead.

 * the size of each txg (meaning the amount of dirty data written, and thus the
time it takes to write out) is now controlled differently.  There is no longer
an explicit time goal; the primary determinant is amount of dirty data.
Systems that are under light or medium load will now often see that a txg is
always syncing, but the impact to performance (e.g. read latency) is minimal.
Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this.

 * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression,
checksum, etc.  This improves latency by not allowing these CPU-intensive tasks
to consume all CPU (on machines with at least 4 CPU's; the percentage is
rounded up).

--matt

APPENDIX: problems with the current i/o scheduler

The current ZFS i/o scheduler (vdev_queue.c) is deadline based.  The problem
with this is that if there are always i/os pending, then certain classes of i/
os can see very long delays.

For example, if there are always synchronous reads outstanding, then no async
writes will be serviced until they become "past due".  One symptom of this
situation is that each pass of the txg sync takes at least several seconds
(typically 3 seconds).

If many i/os become "past due" (their deadline is in the past), then we must
service all of these overdue i/os before any new i/os.  This happens when we
enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in
the future.  If we can't complete all the i/os in 2.5 seconds (e.g. because
there were always reads pending), then these i/os will become past due.  Now we
must service all the "async" writes (which could be hundreds of megabytes)
before we service any reads, introducing considerable latency to synchronous i/
os (reads or ZIL writes).

Notes on porting to ZFS on Linux:

- zio_t gained new members io_physdone and io_phys_children.  Because
  object caches in the Linux port call the constructor only once at
  allocation time, objects may contain residual data when retrieved
  from the cache. Therefore zio_create() was updated to zero out the two
  new fields.

- vdev_mirror_pending() relied on the depth of the per-vdev pending queue
  (vq->vq_pending_tree) to select the least-busy leaf vdev to read from.
  This tree has been replaced by vq->vq_active_tree which is now used
  for the same purpose.

- vdev_queue_init() used the value of zfs_vdev_max_pending to determine
  the number of vdev I/O buffers to pre-allocate.  That global no longer
  exists, so we instead use the sum of the *_max_active values for each of
  the five I/O classes described above.

- The Illumos implementation of dmu_tx_delay() delays a transaction by
  sleeping in condition variable embedded in the thread
  (curthread->t_delay_cv).  We do not have an equivalent CV to use in
  Linux, so this change replaced the delay logic with a wrapper called
  zfs_sleep_until(). This wrapper could be adopted upstream and in other
  downstream ports to abstract away operating system-specific delay logic.

- These tunables are added as module parameters:

  zfs_dirty_data_max_percent
  zfs_delay_min_dirty_percent
  zfs_dirty_data_max
  zfs_dirty_data_max_max
  zfs_dirty_data_sync
  zfs_delay_scale

  The latter four have type unsigned long, whereas they are uint64_t in
  Illumos.  This accommodates Linux's module_param() supported types, but
  means they may overflow on 32-bit architectures.

- Fixed reversed logic in comment above zfs_delay_scale declaration.

- Replaced dmu_tx_write_limit in the dmu_tx kstat file
  with dmu_tx_dirty_delay and dmu_tx_dirty_over_max.  The first counts
  how many times a transaction has been delayed because the pool dirty
  data has exceeded zfs_delay_min_dirty_percent.  The latter counts how
  many times the pool dirty data has exceeded zfs_dirty_data_max (which
  we expect to never happen).

- The original patch would have regressed the bug fixed in
  zfsonlinux/zfs@c418410, which prevented users from setting the
  zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE.
  A similar fix is added to vdev_queue_aggregate().

References:
        http://www.illumos.org/issues/4045
        illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e

Ported-by: Ned Bass <bass6@llnl.gov>