iosched: prevent aliased requests from starving other I/O

Hi, Jens,

If you recall, I posted an RFC patch for this back in July of last year:
http://lkml.org/lkml/2010/7/13/279

The basic problem is that a process can issue a never-ending stream of
async direct I/Os to the same sector on a device, thus starving out
other I/O in the system (due to the way the alias handling works in both
cfq and deadline).  The solution I proposed back then was to start
dispatching from the fifo after a certain number of aliases had been
dispatched.  Vivek asked why we had to treat aliases differently at all,
and I never had a good answer.  So, I put together a simple patch which
allows aliases to be added to the rb tree (it adds them to the right,
though that doesn't matter as the order isn't guaranteed anyway).  I
think this is the preferred solution, as it doesn't break up time slices
in CFQ or batches in deadline.  I've tested it, and it does solve the
starvation issue.  Let me know what you think.

Cheers,
Jeff

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
lib/memcopy: use glibc version

the kernel's memcpy and memmove is very inefficient. But the glibc version is
quite fast, in some cases it is 10 times faster than the kernel version. So I
introduce some memory copy macros and functions of the glibc to improve the
kernel version's performance.

The strategy of the memory functions is:
1. Copy bytes until the destination pointer is aligned.
2. Copy words in unrolled loops.  If the source and destination are not
   aligned in the same way, use word memory operations, but shift and merge
   two read words before writing.
3. Copy the few remaining bytes.

Signed-off-by: Miao Xie <miaox*******>
lib/string: use glibc version

the performance of memcpy and memmove of the general version is very
inefficient, this patch improved them.

Signed-off-by: Miao Xie <miaox*******>
Optimized ARM RWSEM algorithm

RWSEM implementation for ARM using atomic functions.
Heavily based on arch/sh/include/asm/rwsem.h

Signed-off-by: Ashwin Chaugule <ashwinc@codeaurora.org>
Remove ARM sha1 routines

Since commit 8827a4a6b397b07a341ba7fd36ffb91a7835207d
("lib/sha1: use the git implementation of SHA-1"), the ARM SHA1
routines no longer work. The reason? They depended on the larger
320-byte workspace, and now the sha1 workspace is just 16 words
(64 bytes). So the assembly version would overwrite the stack randomly.

The optimized asm version is also probably slower than the new improved
C version, so there's no reason to keep it around.  At least that was
the case in git, where what appears to be the same assembly language
version was removed two years ago because the optimized C BLK_SHA1 code
was faster.

Reported-and-tested-by: Joachim Eastwood <manabian@gmail.com>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Cc: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/sha1: use the git implementation of SHA-1

For ChromiumOS, we use SHA-1 to verify the integrity of the root
filesystem.  The speed of the kernel sha-1 implementation has a major
impact on our boot performance.

To improve boot performance, we investigated using the heavily optimized
sha-1 implementation used in git.  With the git sha-1 implementation, we
see a 11.7% improvement in boot time.

10 reboots, remove slowest/fastest.

Before:

  Mean: 6.58 seconds Stdev: 0.14

After (with git sha-1, this patch):

  Mean: 5.89 seconds Stdev: 0.07

The other cool thing about the git SHA-1 implementation is that it only
needs 64 bytes of stack for the workspace while the original kernel
implementation needed 320 bytes.

Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Cc: Nicolas Pitre <nico@cam.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David S. Miller <davem@davemloft.net>
Cc: linux-crypto@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
rcu: move struct rcu_head to its own file for SLQB and Netfilter use
include/filter.h: add missing rcu_types.h for kernel usage
ARM: net: JIT compiler for packet filters

based of Matt Evans's PPC64 implementation.

The compiler generates ARM instructions but interworking is
supported for Thumb2 kernels.

Supports both little and big endian. Unaligned loads are emitted
for ARMv6+. Not all the BPF opcodes that deal with ancillary data
are supported. The scratch memory of the filter lives on the stack.
Hardware integer division is used if it is available.

Enabled in the same way as for x86-64 and PPC64:

	echo 1 > /proc/sys/net/core/bpf_jit_enable

A value greater than 1 enables opcode output.

Signed-off-by: Mircea Gherzan <mgherzan@xxxxxxxxx>
ARM: net: JIT compiler for packet filters enabled by default
scheduler: minor improvement to pick_next_highest_task_rt

Avoid extra work by continuing on to the next rt_rq if the highest prio task
in current rt_rq is the same priority as our candidate task.

Signed-off-by: Michael J Wang <mjwang@broadcom.com>
msm: cpufreq: Check cpufreq_frequency_table NULL

This is required during single kernel binary support where one target
supports cpufreq and other target is at the initial stages of bringup.
Since we cannot remove CONFIG_CPU_FREQ_MSM from the config file, but
still support the boot on both of them adding a check for targets where
table is not initialized by the acpu clock driver.

Change-Id: I5f52c246586f0c0378a1b2873a064ef69601e3c6
Signed-off-by: Taniya Das <tdas@codeaurora.org>
msm: hotplug: Support cpu hotplug in no PM cases

Add support for hotplug operations to take secondary
CPUs online/offline when CONFIG_PM is turned off.

Change-Id: Iae591f7307a3ea574e3f512714a08da23bcf069b
Signed-off-by: Sathish Ambley <sambley@codeaurora.org>
modified by faux123

Conflicts:

	arch/arm/mach-msm/hotplug.c
kernel: removed GENTLE_FAIR_SLEEPERS for better Android performance
CPUfreq ondemand: update sampling rate without waiting for next sampling

When a new sampling rate is shorter than the current one, (e.g., 1 sec
--> 10 ms) regardless how short the new one is, the current ondemand
mechanism wait for the previously set timer to be expired.

For example, if the user has just expressed that the sampling rate
should be 10 ms from now and the previous was 1000 ms, the new rate may
become effective 999 ms later, which could be not acceptable for the
user if the user has intended to speed up sampling because the system is
expected to react to CPU load fluctuation quickly from __now__.

In order to address this issue, we need to cancel the previously set
timer (schedule_delayed_work) and reset the timer if resetting timer is
expected to trigger the delayed_work ealier.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
lib/vsprintf: replace link to Draft by final RFC number

The draft has evolved to RFC 5952.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
lib: make _tolower() public

This function is required by *printf and kstrto* functions that are
located in the different modules.  This patch makes _tolower() public.
However, it's good idea to not use the helper outside of mentioned
functions.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/kstrtox: common code between kstrto*() and simple_strto*() functions

Currently termination logic (\0 or \n\0) is hardcoded in _kstrtoull(),
avoid that for code reuse between kstrto*() and simple_strtoull().
Essentially, make them different only in termination logic.

simple_strtoull() (and scanf(), BTW) ignores integer overflow, that's a
bug we currently don't have guts to fix, making KSTRTOX_OVERFLOW hack
necessary.

Almost forgot: patch shrinks code size by about ~80 bytes on x86_64.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
vsprintf: make %pV handling compatible with kasprintf()

kasprintf() (and potentially other functions that I didn't run across so
far) want to evaluate argument lists twice.  Caring to do so for the
primary list is obviously their job, but they can't reasonably be
expected to check the format string for instances of %pV, which however
need special handling too: On architectures like x86-64 (as opposed to
e.g.  ix86), using the same argument list twice doesn't produce the
expected results, as an internally managed cursor gets updated during
the first run.

Fix the problem by always acting on a copy of the original list when
handling %pV.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
procfs: add num_to_str() to speed up /proc/stat

== stat_check.py
num = 0
with open("/proc/stat") as f:
        while num < 1000 :
                data = f.read()
                f.seek(0, 0)
                num = num + 1
==

perf shows

    20.39%  stat_check.py  [kernel.kallsyms]    [k] format_decode
    13.41%  stat_check.py  [kernel.kallsyms]    [k] number
    12.61%  stat_check.py  [kernel.kallsyms]    [k] vsnprintf
    10.85%  stat_check.py  [kernel.kallsyms]    [k] memcpy
     4.85%  stat_check.py  [kernel.kallsyms]    [k] radix_tree_lookup
     4.43%  stat_check.py  [kernel.kallsyms]    [k] seq_printf

This patch removes most of calls to vsnprintf() by adding num_to_str()
and seq_print_decimal_ull(), which prints decimal numbers without rich
functions provided by printf().

On my 8cpu box.
== Before patch ==
[root@bluextal test]# time ./stat_check.py

real    0m0.150s
user    0m0.026s
sys     0m0.121s

== After patch ==
[root@bluextal test]# time ./stat_check.py

real    0m0.055s
user    0m0.022s
sys     0m0.030s

[akpm@linux-foundation.org: remove incorrect comment, use less statck in num_to_str(), move comment from .h to .c, simplify seq_put_decimal_ull()]
[andrea@betterlinux.com: avoid breaking the ABI in /proc/stat]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrea Righi <andrea@betterlinux.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Turner <pjt@google.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
backported from Linux 3.4-rc4 to Linux 3.0.x by faux123