lkml.org 
[lkml]   [2015]   [Nov]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [patch 3/3] vmstat: Create our own workqueue
From
Date
Christoph Lameter wrote:
> On Sat, 31 Oct 2015, Tetsuo Handa wrote:
>
> > Then, you need to update below description (or drop it) because
> > patch 3/3 alone will not guarantee that the counters are up to date.
>
> The vmstat system does not guarantee that the counters are up to date
> always. The whole point is the deferral of updates for performance
> reasons. They are updated *at some point* within stat_interval. That needs
> to happen and that is what this patchset is fixing.

So, if you refer to the blocking of the execution of vmstat updates,
description for patch 3/3 sould be updated to something like below?

----------
Since __GFP_WAIT memory allocations do not call schedule()
when there is nothing to reclaim, and workqueue does not kick
remaining workqueue items unless in-flight workqueue item calls
schedule(), __GFP_WAIT memory allocation requests by workqueue
items can block vmstat_update work item forever.

Since zone_reclaimable() decision depends on vmstat counters
to be up to dated, a silent lockup occurs because a workqueue
item doing a __GFP_WAIT memory allocation request continues
using outdated vmstat counters.

In order to fix this problem, we need to allocate a dedicated
workqueue for vmstat. Note that this patch itself does not fix
lockup problem. Tejun will develop a patch which detects lockup
situation and kick remaining workqueue items.
----------


\
 
 \ /
  Last update: 2015-11-06 12:41    [W:0.079 / U:0.100 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site