[PATCH] makedumpfile: turn off mmap for free page scan

HATAYAMA Daisuke d.hatayama at jp.fujitsu.com
Wed May 22 03:38:56 EDT 2013

(2013/05/22 15:57), Atsushi Kumagai wrote:
> On Wed, 15 May 2013 13:43:59 -0500
> Cliff Wickman <cpw at sgi.com> wrote:
>> From: Cliff Wickman <cpw at sgi.com>
>> Because addresses of each successive page structure are often descending
>> it is much faster to use read()'s, so set off info->flag_usemmap
>> while doing exclude_free_page().
>> Signed-off-by: Cliff Wickman <cpw at sgi.com>
> Sounds good.
> BTW, do you have a speed measurement like your another patch ?

Also how about keeping mmap mode and reducing mapping size temporarily 
to 4KiB?

>> I find this to speed the scan of page structures for a 1TB system from
>> 60sec to 30sec.

I don't know which this measured time indicates. Only free pages 
filtering or free pages filtering plus unnecessary pages filtering?


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