From: Andi Kleen <ak@suse.de>
To: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
manfred@colorfullife.com
Subject: Re: Weird schedule delay time for cache_reap()
Date: Thu, 27 Oct 2005 10:37:08 +0200 [thread overview]
Message-ID: <200510271037.08853.ak@suse.de> (raw)
In-Reply-To: <200510270228.j9R2SWg27777@unix-os.sc.intel.com>
On Thursday 27 October 2005 04:28, Chen, Kenneth W wrote:
> can't convince myself that the 2nd argument in schedule_delayed_work
>called from cache_reap() function make any sense:
>static void cache_reap(void *unused)
>{ ...
>schedule_delayed_work(&__get_cpu_var(reap_work), REAPTIMEOUT_CPUC +
smp_processor_id());
>
> Suppose one have a lucky 1024-processor big iron numa box,
> cpu0 will do cache_reap every 2 sec (REAPTIMEOUT_CPUC = 2*HZ).
> cpu512 will do cache_reap every 4 sec,
> cpu1023 will do cache_reap every 6 sec.
>
> Is the skew intentional on different CPU? Why different interval for
> different cpu#?
It looks like a buggy attempt to make the timers not cluster.
The +smp_processor_id() should be probably only done on the first iteration.
start_cpu_timer() does this already, so removing it should be ok.
-Andi
WARNING: multiple messages have this Message-ID (diff)
From: Andi Kleen <ak@suse.de>
To: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
manfred@colorfullife.com
Subject: Re: Weird schedule delay time for cache_reap()
Date: Thu, 27 Oct 2005 10:37:08 +0200 [thread overview]
Message-ID: <200510271037.08853.ak@suse.de> (raw)
In-Reply-To: <200510270228.j9R2SWg27777@unix-os.sc.intel.com>
On Thursday 27 October 2005 04:28, Chen, Kenneth W wrote:
> can't convince myself that the 2nd argument in schedule_delayed_work
>called from cache_reap() function make any sense:
>static void cache_reap(void *unused)
>{ ...
>schedule_delayed_work(&__get_cpu_var(reap_work), REAPTIMEOUT_CPUC +
smp_processor_id());
>
> Suppose one have a lucky 1024-processor big iron numa box,
> cpu0 will do cache_reap every 2 sec (REAPTIMEOUT_CPUC = 2*HZ).
> cpu512 will do cache_reap every 4 sec,
> cpu1023 will do cache_reap every 6 sec.
>
> Is the skew intentional on different CPU? Why different interval for
> different cpu#?
It looks like a buggy attempt to make the timers not cluster.
The +smp_processor_id() should be probably only done on the first iteration.
start_cpu_timer() does this already, so removing it should be ok.
-Andi
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next prev parent reply other threads:[~2005-10-27 8:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-27 2:28 Weird schedule delay time for cache_reap() Chen, Kenneth W
2005-10-27 2:28 ` Chen, Kenneth W
2005-10-27 8:37 ` Andi Kleen [this message]
2005-10-27 8:37 ` Andi Kleen
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