[lkml]   [2012]   [Jan]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] mm: vmscan: fix setting reclaim mode
On Wed, Jan 11, 2012 at 12:44 AM, Mel Gorman <> wrote:
> On Tue, Jan 10, 2012 at 11:58:03PM +0800, Hillf Danton wrote:
>> From: Hillf Danton <>
>> [PATCH] mm: vmscan: fix setting reclaim mode
>> The comment says, initially assume we are entering either lumpy reclaim or
>> reclaim/compaction, and depending on the reclaim order, we will either set the
>> sync mode or just reclaim order-0 pages later.
>> On other hand, order-0 reclaim, instead of sync reclaim, is expected when
>> under memory pressure, but the check for memory pressure is incorrect,
>> leading to sync reclaim at low reclaim priorities.
>> And the result is sync reclaim is set for high priorities.
> using RECLAIM_MODE_LUMPYRECLAIM, it should only be set when reclaim
> is under memory pressure and failing to reclaim the necessry pages
> (priority < DEF_PRIORITY - 2). Once in symc reclaim, reclaim will call
> wait_on_page_writeback() on dirty pages which potentially leads to
> significant stalls (one of the reasons why RECLAIM_MODE_LUMPYRECLAIM
> sucks and why compaction is preferred). Your patch means sync reclaim
> is used even when priority == DEF_PRIORITY. This is unexpected.
> Your changelog really needs to explain what the problem is that you
> have encountered and why this patch fixes it. It's not like some of
> your other patches which were minor performance optimisations that
> were self-evident.
Hi Mel

To avoid another step in wrong direction, I'd goto bed now,
it is about 1:09 AM.
When sane again, I will try to understand your comment.


 \ /
  Last update: 2012-01-10 18:01    [W:0.042 / U:22.944 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site