android_kernel_xiaomi_sm8350/arch/x86
Arjan van de Ven 9bcbdd9c58 x86, timers: Check for pending timers after (device) interrupts
Now that range timers and deferred timers are common, I found a
problem with these using the "perf timechart" tool. Frans Pop also
reported high scheduler latencies via LatencyTop, when using
iwlagn.

It turns out that on x86, these two 'opportunistic' timers only get
checked when another "real" timer happens. These opportunistic
timers have the objective to save power by hitchhiking on other
wakeups, as to avoid CPU wakeups by themselves as much as possible.

The change in this patch runs this check not only at timer
interrupts, but at all (device) interrupts. The effect is that:

 1) the deferred timers/range timers get delayed less

 2) the range timers cause less wakeups by themselves because
    the percentage of hitchhiking on existing wakeup events goes up.

I've verified the working of the patch using "perf timechart", the
original exposed bug is gone with this patch. Frans also reported
success - the latencies are now down in the expected ~10 msec
range.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Tested-by: Frans Pop <elendil@planet.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20091008064041.67219b13@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-08 17:27:27 +02:00
..
boot Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-09-26 10:13:35 -07:00
configs
crypto Merge branch 'x86-cpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-09-14 07:57:32 -07:00
ia32 x86: Don't leak 64-bit kernel register values to 32-bit processes 2009-10-01 11:24:26 +02:00
include/asm KVM: add support for change_pte mmu notifiers 2009-10-04 17:04:53 +02:00
kernel x86, timers: Check for pending timers after (device) interrupts 2009-10-08 17:27:27 +02:00
kvm KVM: add support for change_pte mmu notifiers 2009-10-04 17:04:53 +02:00
lguest lguest: move panic notifier registration to its expected place. 2009-09-23 22:26:44 +09:30
lib x86: Don't generate cmpxchg8b_emu if CONFIG_X86_CMPXCHG64=y 2009-10-01 08:42:24 +02:00
math-emu
mm Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-09-26 10:13:35 -07:00
oprofile perf: Do the big rename: Performance Counters -> Performance Events 2009-09-21 14:28:04 +02:00
pci const: mark struct vm_struct_operations 2009-09-27 11:39:25 -07:00
power x86: Remove final bits of CONFIG_X86_OLD_MCE 2009-09-18 08:31:23 +02:00
vdso kbuild: rename ld-option to cc-ldoption 2009-09-20 12:27:42 +02:00
video
xen const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
Kbuild
Kconfig x86, SLUB: Remove unused CONFIG FAST_CMPXCHG_LOCAL 2009-10-01 10:59:08 +02:00
Kconfig.cpu x86: Optimize cmpxchg64() at build-time some more 2009-10-01 08:01:08 +02:00
Kconfig.debug
Makefile kbuild: use INSTALLKERNEL to select customized installkernel script 2009-09-20 12:18:14 +02:00
Makefile_32.cpu