lkml.org 
[lkml]   [2014]   [Feb]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] mm:prototype for the updated swapoff implementation
On 02/19/2014 04:27 PM, Andrew Morton wrote:
> On Tue, 18 Feb 2014 16:35:22 -0800 Kelley Nielsen <kelleynnn@gmail.com> wrote:
>
>> The function try_to_unuse() is of quadratic complexity, with a lot of
>> wasted effort. It unuses swap entries one by one, potentially iterating
>> over all the page tables for all the processes in the system for each
>> one.
>>
>> This new proposed implementation of try_to_unuse simplifies its
>> complexity to linear. It iterates over the system's mms once, unusing
>> all the affected entries as it walks each set of page tables. It also
>> makes similar changes to shmem_unuse.
>>
>> Improvement
>>
>> swapoff was called on a swap partition containing about 50M of data,
>> and calls to the function unuse_pte_range were counted.
>>
>> Present implementation....about 22.5M calls.
>> Prototype.................about 7.0K calls.
>
> Do you have situations in which swapoff is taking an unacceptable
> amount of time? If so, please update the changelog to provide full
> details on this, with before-and-after timing measurements.

I have seen plenty of that. With just a few GB in swap space in
use, on a system with 24GB of RAM, and about a dozen GB in use
by various processes, I have seen swapoff take several hours of
CPU time.

--
All rights reversed.


\
 
 \ /
  Last update: 2014-02-19 23:41    [W:0.082 / U:4.868 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site