lkml.org 
[lkml]   [2012]   [Feb]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 9/10] mm/memcg: move lru_lock into lruvec
On Wed, 22 Feb 2012, Konstantin Khlebnikov wrote:
> Hugh Dickins wrote:
> >
> > I'll have to come back to think about your locking later too;
> > or maybe that's exactly where I need to look, when investigating
> > the mm_inline.h:41 BUG.
>
> pages_count[] updates looks correct.
> This really may be bug in locking, and this VM_BUG_ON catch it before
> list-debug.

I've still not got into looking at it yet.

You're right to mention DEBUG_LIST: I have that on some of the machines,
and I would expect that to be the first to catch a mislocking issue.

In the past my problems with that BUG (well, the spur to introduce it)
came from hugepages.

> >
> > But at first sight, I have to say I'm very suspicious: I've never found
> > PageLRU a good enough test for whether we need such a lock, because of
> > races with those pages on percpu lruvec about to be put on the lru.
> >
> > But maybe once I look closer, I'll find that's handled by your changes
> > away from lruvec; though I'd have thought the same issue exists,
> > independent of whether the pending pages are in vector or list.
>
> Are you talking about my per-cpu page-lists for lru-adding?

Yes.

> This is just an unnecessary patch, I don't know why I include it into v2 set.
> It does not protect anything.

Okay.

Hugh


\
 
 \ /
  Last update: 2012-02-21 23:15    [from the cache]
©2003-2011 Jasper Spaans