lkml.org 
[lkml]   [2014]   [Jul]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] swap: remove the struct cpumask has_work
On 7/31/2014 7:51 AM, Michal Hocko wrote:
> On Thu 31-07-14 11:30:19, Lai Jiangshan wrote:
>> It is suggested that cpumask_var_t and alloc_cpumask_var() should be used
>> instead of struct cpumask. But I don't want to add this complicity nor
>> leave this unwelcome "static struct cpumask has_work;", so I just remove
>> it and use flush_work() to perform on all online drain_work. flush_work()
>> performs very quickly on initialized but unused work item, thus we don't
>> need the struct cpumask has_work for performance.
> Why? Just because there is general recommendation for using
> cpumask_var_t rather than cpumask?
>
> In this particular case cpumask shouldn't matter much as it is static.
> Your code will work as well, but I do not see any strong reason to
> change it just to get rid of cpumask which is not on stack.

The code uses for_each_cpu with a cpumask to avoid waking cpus that don't
need to do work. This is important for the nohz_full type functionality,
power efficiency, etc. So, nack for this change.

--
Chris Metcalf, Tilera Corp.
http://www.tilera.com



\
 
 \ /
  Last update: 2014-07-31 19:01    [W:0.893 / U:0.580 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site