lkml.org 
[lkml]   [2017]   [Jul]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using page->lru field
On Tue, Jul 4, 2017 at 10:51 PM, Michal Hocko <mhocko@kernel.org> wrote:
> On Mon 03-07-17 17:14:14, Jérôme Glisse wrote:
>> HMM pages (private or public device pages) are ZONE_DEVICE page and
>> thus you can not use page->lru fields of those pages. This patch
>> re-arrange the uncharge to allow single page to be uncharge without
>> modifying the lru field of the struct page.
>>
>> There is no change to memcontrol logic, it is the same as it was
>> before this patch.
>
> What is the memcg semantic of the memory? Why is it even charged? AFAIR
> this is not a reclaimable memory. If yes how are we going to deal with
> memory limits? What should happen if go OOM? Does killing an process
> actually help to release that memory? Isn't it pinned by a device?
>
> For the patch itself. It is quite ugly but I haven't spotted anything
> obviously wrong with it. It is the memcg semantic with this class of
> memory which makes me worried.
>

This is the HMM CDM case. Memory is normally malloc'd and then
migrated to ZONE_DEVICE or vice-versa. One of the things we did
discuss was seeing ZONE_DEVICE memory in user page tables.

Balbir Singh.

\
 
 \ /
  Last update: 2017-07-05 05:19    [W:0.111 / U:4.592 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site