Commit-ID: f8e617f4582995f7c25ef25b4167213120ad122b Gitweb: http://git.kernel.org/tip/f8e617f4582995f7c25ef25b4167213120ad122b Author: Mike Galbraith <bitbuc...@online.de> AuthorDate: Sat, 18 Jan 2014 17:14:44 +0100 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Mon, 16 Mar 2015 11:14:22 +0100
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 <bitbuc...@online.de> Cc: <sta...@vger.kernel.org> # 3.10+ Cc: Borislav Petkov <b...@alien8.de> Cc: H. Peter Anvin <h...@zytor.com> Cc: Ian Malone <ibmal...@gmail.com> Cc: Josh Boyer <jwbo...@redhat.com> Cc: Len Brown <len.br...@intel.com> Cc: Len Brown <l...@kernel.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Mike Galbraith <efa...@gmx.de> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/1390061684.5566.4.ca...@marge.simpson.net [ Ported to recent kernel, added comments about the quirk. ] Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/kernel/process.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index da06f74..6ad8a63 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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
