[patch] iosched: prevent aliased requests from starving other I/O

http://lkml.indiana.edu/hypermail/linux/kernel/1106.0/00548.html

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
Optimized Async I/O
Lower VFS cache pressure

VFS cache pressure defines how readily the kernel will drop caches to recovery memory.
We lower it here to allow more RAM to be used for caches, which should increase
performance of frequently used apps.  The kernel will still drop the caches when we
need the memory.  We don't make it too low, because otherwise, performance could
suffer due to insufficient free memory.
Increase dirty ratio

Delay writing of data to SD for as long as possible to improve performance
Reduce swappiness

When using swap, don't swap until necessary.
Added optimized ARM RWSEM algorithm

Conflicts:
	arch/arm/configs/vigor_aosp_defconfig
Use the git implementation of SHA-1. From MikeC84.
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>
Increase default SD readahead
Disable GENTLE_FAIR_SLEEPERS
mm: optimize SLUB
Add dynamic writeback feature from 3.1
ARM: clean up idle handlers

Let's factor out the need_resched() check instead of having it duplicated
in every pm_idle implementations to avoid inconsistencies (omap2_pm_idle
is missing it already).

The forceful re-enablement of IRQs after pm_idle has returned can go.
The warning certainly doesn't trigger for existing users.

To get rid of the pm_idle calling convention oddity, let's introduce
arm_pm_idle() allowing for the local_irq_enable() to be factored out
from SOC specific implementations. The default pm_idle function becomes
a wrapper for arm_pm_idle and it takes care of enabling IRQs closer to
where they are initially disabled.

And finally move the comment explaining the reason for that turning off
of IRQs to a more proper location.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Acked-and-tested-by: Jamie Iles <jamie@jamieiles.com>
optimize checksum routines
mm: compaction: make compact_control order signed

"order" is -1 when compacting via /proc/sys/vm/compact_memory.  Making
it unsigned causes a bug in __compact_pgdat() when we test:

	if (cc->order < 0 || !compaction_deferred(zone, cc->order))
		compact_zone(zone, cc);

[akpm@linux-foundation.org: make __compact_pgdat()'s comparison match other code sites]
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Minchan Kim <minchan@kernel.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add topology.c
[PATCH] ARM Topology by Linaro team
allows individual queue'ing of tasks to cores by the scheduler
Enable Linaro ARM multicore topology scheduler
Allow reading of MPIDR on ARM