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Date: Tue, 11 May 2004 12:11:26 -0700
From: Andrew Morton <akpm@osdl.org>
To: "Geoff Gustafson" <geoff@linux.jf.intel.com>
Cc: linux-kernel@vger.kernel.org, kenneth.w.chen@intel.com,
       Ingo Molnar <mingo@elte.hu>
Subject: Re: [RFC] [PATCH] Performance of del_timer_sync
Message-Id: <20040511121126.73f5fdeb.akpm@osdl.org>
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"Geoff Gustafson" <geoff@linux.jf.intel.com> wrote:
>
> Andrew Morton wrote:
> > Geoff Gustafson <geoff@linux.jf.intel.com> wrote:
> >> 
> >> I started this patch based on profiling an enterprise database
> >>  application on a 32p IA64 NUMA machine, where del_timer_sync was
> >>  one of the top few functions taking CPU time in the kernel.
> > 
> > Do you know where it's being called from?
> 
> OK, the main sources were:
> 
> sys_semtimedop() -> schedule_timeout()
> 
> sys_io_getevents() -> read_events() -> clear_timeout()
> 

OK, thanks.  schedule_timeout()!  Ow.

Ingo, why is this not sufficient?


diff -puN kernel/timer.c~a kernel/timer.c
--- 25/kernel/timer.c~a	2004-05-11 12:10:28.695557600 -0700
+++ 25-akpm/kernel/timer.c	2004-05-11 12:10:42.820410296 -0700
@@ -331,6 +331,8 @@ int del_timer_sync(struct timer_list *ti
 
 del_again:
 	ret += del_timer(timer);
+	if (!ret)
+		return 0;
 
 	for_each_cpu(i) {
 		base = &per_cpu(tvec_bases, i);

_