lkml.org 
[lkml]   [2009]   [May]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 1/5] mm: Add __GFP_NO_OOM_KILL flag
Date
On Thursday 07 May 2009, David Rientjes wrote:
> On Thu, 7 May 2009, Andrew Morton wrote:
>
> > > > All of your tasks are in D state other than kthreads, right? That means
> > > > they won't be in the oom killer (thus no zones are oom locked), so you can
> > > > easily do this
> > > >
> > > > struct zone *z;
> > > > for_each_populated_zone(z)
> > > > zone_set_flag(z, ZONE_OOM_LOCKED);
> > > >
> > > > and then
> > > >
> > > > for_each_populated_zone(z)
> > > > zone_clear_flag(z, ZONE_OOM_LOCKED);
> > > >
> > > > The serialization is done with trylocks so this will never invoke the oom
> > > > killer because all zones in the allocator's zonelist will be oom locked.
> > > >
> > > > Why does this not work for you?
> > >
> > > Well, it might work too, but why are you insisting? How's it better than
> > > __GFP_NO_OOM_KILL, actually?
> > >
> > > Andrew, what do you think about this?
> >
> > I don't think I understand the proposal. Is it to provide a means by
> > which PM can go in and set a state bit against each and every zone? If
> > so, that's still a global boolean, only messier.
> >
>
> Why can't it be global while preallocating memory for hibernation since
> nothing but kthreads could allocate at this point and if the system is oom
> then the oom killer wouldn't be able to do anything anyway since it can't
> kill them?
>
> The fact is that _all_ allocations here are implicitly __GFP_NO_OOM_KILL
> whether it specifies it or not since the oom killer would simply kill a
> task in D state which can't exit or free memory and subsequent allocations
> would make the oom killer a no-op because there's an eligible task with
> TIF_MEMDIE set. The only thing you're saving with __GFP_NO_OOM_KILL is
> calling the oom killer in a first place and killing an unresponsive task

That's exactly what we're trying to do. We don't want tasks to get killed just
because we're freeing memory for hibernation image.

> but that would have to happen anyway when thawed since the system is oom
> (or otherwise lockup for GFP_KERNEL with order < PAGE_ALLOC_COSTLY_ORDER).

Are you sure? The image memory is freed before thawing tasks.


\
 
 \ /
  Last update: 2009-05-07 23:39    [W:1.150 / U:0.804 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site