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Chen, Kenneth W 1e185b97b4 [PATCH] ia64: cpu_idle performance bug fix 
Our performance validation on 2.6.15-rc1 caught a disastrous performance
regression on ia64 with netperf (-98%) and volanomark (-58%) compares to
previous kernel version 2.6.14-git7.  See the following chart (result
group 1 & 2).

  http://kernel-perf.sourceforge.net/results.machine_id=26.html

We have root caused it to commit 64c7c8f885

This changeset broke the ia64 task resched notification.  In
sched.c:resched_task(), a reschedule IPI is conditioned upon
TIF_POLLING_NRFLAG.  However, the above changeset unconditionally set
the polling thread flag for idle tasks regardless whether pal_halt_light
is in use or not.  As a result, resched IPI is not sent from
resched_task().  And since the default behavior on ia64 is to use
pal_halt_light, we end up delaying the rescheduling task until next
timer tick, and thus cause the performance regression.

This fixes the performance bug.  I'm glad our performance suite is
turning up bad performance bug like this in time.

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-15 15:50:51 -08:00
..
configs [IA64] 4-level page tables 2005-11-11 09:37:29 -08:00
dig Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
hp [PATCH] ia64: fix-up schedule_timeout() usage 2005-11-07 07:53:56 -08:00
ia32 [PATCH] remove ioctl32_handler_t 2005-11-09 07:56:00 -08:00
kernel [PATCH] ia64: cpu_idle performance bug fix 2005-11-15 15:50:51 -08:00
lib Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6 2005-10-28 21:09:26 -07:00
mm Pull context-bitmap into release branch 2005-11-10 10:39:49 -08:00
oprofile [PATCH] Move Kprobes and Oprofile to "Instrumentation Support" menu 2005-11-07 07:53:35 -08:00
pci [IA64] add the MMIO regions that are translated to I/O port space to /proc/iomem 2005-11-08 10:09:40 -08:00
scripts Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sn [IA64-SGI] set altix preferred console 2005-11-11 11:24:26 -08:00
defconfig [IA64] 4-level page tables 2005-11-11 09:37:29 -08:00
install.sh Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
Kconfig Merge x86-64 update from Andi 2005-11-14 19:56:02 -08:00
Kconfig.debug [PATCH] Move Kprobes and Oprofile to "Instrumentation Support" menu 2005-11-07 07:53:35 -08:00
Makefile [IA64] fix circular dependency on generation of asm-offsets.h 2005-09-13 08:50:39 -07:00
module.lds Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00