linux-kernel - Re: [RFC PATCH 0/5] crash dump bitmap: scan memory pages in kernel to speedup kernel dump process

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Message-ID: <513D9DB1.7040100@hp.com>
Date:	Mon, 11 Mar 2013 17:02:41 +0800
From:	Jingbai Ma <jingbai.ma@...com>
To:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
CC:	jingbai.ma@...com, vgoyal@...hat.com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, lisa.mitchell@...com,
	mingo@...hat.com, kumagai-atsushi@....nes.nec.co.jp,
	ebiederm@...ssion.com, hpa@...or.com, yinghai@...nel.org
Subject: Re: [RFC PATCH 0/5] crash dump bitmap: scan memory pages in kernel
 to speedup kernel dump process

On 03/09/2013 12:31 PM, HATAYAMA Daisuke wrote:
> From: Jingbai Ma<jingbai.ma@...com>
> Subject: Re: [RFC PATCH 0/5] crash dump bitmap: scan memory pages in kernel to speedup kernel dump process
> Date: Fri, 8 Mar 2013 18:06:31 +0800
>
>> On 03/07/2013 11:21 PM, Vivek Goyal wrote:
>>> On Thu, Mar 07, 2013 at 10:58:18PM +0800, Jingbai Ma wrote:
> ...
>>> First of all 64MB per TB should not be a huge deal. And makedumpfile
>>> also has this cyclic mode where you process a map, discard it and then
>>> move on to next section. So memory usage remains constant at the
>>> expense
>>> of processing time.
>>
>> Yes, that's true. But in cyclic mode, makedumpfile will have to
>> write/read bitmap from storage, it will also impact the performance.
>> I have measured the penalty for cyclic mode is about 70%
>> slowdown. Maybe could be faster after mmap implemented.
>
> I guess the slowdown came from the issue that enough VMCOREINFO was
> not provided from the kernel, and unnecessary filtering processing for
> free pages is done multiple times.

Thanks for your comments! It would be very helpful.
I will test it on the machine again.

-- 
Jingbai Ma (jingbai.ma@...com)
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