lkml.org 
[lkml]   [2017]   [Jul]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] mm: don't zero ballooned pages
On 07/31/2017 02:55 PM, Michal Hocko wrote:
> On Mon 31-07-17 12:13:33, Wei Wang wrote:
>> Ballooned pages will be marked as MADV_DONTNEED by the hypervisor and
>> shouldn't be given to the host ksmd to scan.
> Could you point me where this MADV_DONTNEED is done, please?

Sure. It's done in the hypervisor when the balloon pages are received.

Please see line 40 at
https://github.com/qemu/qemu/blob/master/hw/virtio/virtio-balloon.c


>
>> Therefore, it is not
>> necessary to zero ballooned pages, which is very time consuming when
>> the page amount is large. The ongoing fast balloon tests show that the
>> time to balloon 7G pages is increased from ~491ms to 2.8 seconds with
>> __GFP_ZERO added. So, this patch removes the flag.
> Please make it obvious that this is a revert of bb01b64cfab7
> ("mm/balloon_compaction.c: enqueue zero page to balloon device").
>
>

Ok, will do.

Best,
Wei

\
 
 \ /
  Last update: 2017-07-31 09:40    [W:0.054 / U:0.192 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site