Messages in this thread | | | Date | Mon, 21 Apr 2008 16:27:38 +0200 | From | Ingo Molnar <> | Subject | Re: x86: improve default idle |
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* Andrew Morton <akpm@linux-foundation.org> wrote:
> On Fri, 18 Apr 2008 17:37:02 GMT > Linux Kernel Mailing List <linux-kernel@vger.kernel.org> wrote: > > > Gitweb: http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=13af4836b3914b23946f6a8982934e2c828c183f > > Commit: 13af4836b3914b23946f6a8982934e2c828c183f > > Parent: f5149a49f994e5c469ac398af7cdeb8eb612d3a4 > > Author: Ingo Molnar <mingo@elte.hu> > > AuthorDate: Wed Apr 2 13:23:22 2008 +0200 > > Committer: Ingo Molnar <mingo@elte.hu> > > CommitDate: Thu Apr 17 17:41:34 2008 +0200 > > > > x86: improve default idle > > > > Signed-off-by: Ingo Molnar <mingo@elte.hu> > > --- > > arch/x86/kernel/process_32.c | 8 -------- > > arch/x86/kernel/process_64.c | 8 -------- > > 2 files changed, 0 insertions(+), 16 deletions(-) > > > > diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c > > index 08c41ed..3903a8f 100644 > > --- a/arch/x86/kernel/process_32.c > > +++ b/arch/x86/kernel/process_32.c > > @@ -113,16 +113,8 @@ void default_idle(void) > > > > local_irq_disable(); > > if (!need_resched()) { > > - ktime_t t0, t1; > > - u64 t0n, t1n; > > - > > - t0 = ktime_get(); > > - t0n = ktime_to_ns(t0); > > safe_halt(); /* enables interrupts racelessly */ > > local_irq_disable(); > > - t1 = ktime_get(); > > - t1n = ktime_to_ns(t1); > > - sched_clock_idle_wakeup_event(t1n - t0n); > > } > > local_irq_enable(); > > current_thread_info()->status |= TS_POLLING; > > diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c > > index 4f40272..e75ccc8 100644 > > --- a/arch/x86/kernel/process_64.c > > +++ b/arch/x86/kernel/process_64.c > > @@ -107,16 +107,8 @@ void default_idle(void) > > smp_mb(); > > local_irq_disable(); > > if (!need_resched()) { > > - ktime_t t0, t1; > > - u64 t0n, t1n; > > - > > - t0 = ktime_get(); > > - t0n = ktime_to_ns(t0); > > safe_halt(); /* enables interrupts racelessly */ > > local_irq_disable(); > > - t1 = ktime_get(); > > - t1n = ktime_to_ns(t1); > > - sched_clock_idle_wakeup_event(t1n - t0n); > > } > > local_irq_enable(); > > current_thread_info()->status |= TS_POLLING; > > Ingo, what's going on? There is no way that this patch is so obvious > that it doesn't even need a changelog.
sorry, the changelog should be: if a system uses acpi_pm clocksource but default idle method then the overhead of entry/exit measurement is quite noticeable in profiles. The measurement is redundant anyway, as in HLT sched_clock() is still supposed to work fine. (the worst i know of is a slight skew on certain CPUs in HLT)
Ingo
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