linux-kernel - Re: [PATCH V8] Eliminate task stack trace duplication

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Message-ID: <CALWz4iyKDcrLoK4Dtnwwq6OvDAiEyb72iV6dezwKmoZWhkVDSw@mail.gmail.com>
Date:	Thu, 26 Apr 2012 12:33:36 -0700
From:	Ying Han <yinghan@...gle.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, tglx@...utronix.de,
	x86@...nel.org
Subject: Re: [PATCH V8] Eliminate task stack trace duplication

++cc x86 people which I forgot this time ..

--Ying

On Fri, Apr 6, 2012 at 11:57 AM, Rik van Riel <riel@...hat.com> wrote:
> On 04/06/2012 02:45 PM, Ying Han wrote:
>>
>> The problem with small dmesg ring buffer like 512k is that only limited
>> number
>> of task traces will be logged. Sometimes we lose important information
>> only
>> because of too many duplicated stack traces. This problem occurs when
>> dumping
>> lots of stacks in a single operation, such as sysrq-T.
>>
>> This patch tries to reduce the duplication of task stack trace in the dump
>> message by hashing the task stack. The hashtable is a 32k pre-allocated
>> buffer
>> during bootup. Each time if we find the identical task trace in the task
>> stack,
>> we dump only the pid of the task which has the task trace dumped. So it is
>> easy
>> to back track to the full stack with the pid.
>
>
>> Signed-off-by: Ying Han<yinghan@...gle.com>
>
>
> Acked-by: Rik van Riel <riel@...hat.com>
>
> --
> All rights reversed
--
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