diff options
| author | Mike Galbraith <bitbucket@online.de> | 2014-01-18 17:14:44 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-03-16 11:14:22 +0100 |
| commit | f8e617f4582995f7c25ef25b4167213120ad122b (patch) | |
| tree | a7c1a1b1e45b27cc9e36a76ab83396a0e70b04e2 | |
| parent | b253149b843f89cd300cbdbea27ce1f847506f99 (diff) | |
| download | linux-f8e617f4582995f7c25ef25b4167213120ad122b.tar.bz2 | |
sched/idle/x86: Optimize unnecessary mwait_idle() resched IPIs
To fully take advantage of MWAIT, apparently the CLFLUSH instruction needs
another quirk on certain CPUs: proper barriers around it on certain machines.
On a Q6600 SMP system, pipe-test scheduling performance, cross core,
improves significantly:
3.8.13 487.2 KHz 1.000
3.13.0-master 415.5 KHz .852
3.13.0-master+ 415.2 KHz .852 + restore mwait_idle
3.13.0-master++ 488.5 KHz 1.002 + restore mwait_idle + IPI fix
Since X86_BUG_CLFLUSH_MONITOR is already a quirk, don't create a separate
quirk for the extra smp_mb()s.
Signed-off-by: Mike Galbraith <bitbucket@online.de>
Cc: <stable@vger.kernel.org> # 3.10+
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ian Malone <ibmalone@gmail.com>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1390061684.5566.4.camel@marge.simpson.net
[ Ported to recent kernel, added comments about the quirk. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | arch/x86/kernel/process.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index da06f741d2a6..6ad8a6396b75 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -428,18 +428,22 @@ static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c) static void mwait_idle(void) { - if (!need_resched()) { - if (this_cpu_has(X86_BUG_CLFLUSH_MONITOR)) + if (!current_set_polling_and_test()) { + if (this_cpu_has(X86_BUG_CLFLUSH_MONITOR)) { + smp_mb(); /* quirk */ clflush((void *)¤t_thread_info()->flags); + smp_mb(); /* quirk */ + } __monitor((void *)¤t_thread_info()->flags, 0, 0); - smp_mb(); if (!need_resched()) __sti_mwait(0, 0); else local_irq_enable(); - } else + } else { local_irq_enable(); + } + __current_clr_polling(); } void select_idle_routine(const struct cpuinfo_x86 *c) |