lkml.org 
[lkml]   [2017]   [Jul]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [HMM 12/15] mm/migrate: new memory migration helper for use with device memory v4
On Tue, Jul 11, 2017 at 11:42:20AM -0700, Evgeny Baskakov wrote:
> On 7/11/17 11:29 AM, Jerome Glisse wrote:
> > Can you test if attached patch helps ? I am having trouble reproducing
> > this
> > from inside a vm.
> >
> > My theory is that 2 concurrent CPU page fault happens. First one manage to
> > start the migration back to system memory but second one see the migration
> > special entry and call migration_entry_wait() which increase page refcount
> > and this happen before first one check page refcount are ok for migration.
> >
> > For regular migration such scenario is ok as the migration bails out and
> > because page is CPU accessible there is no need to kick again the migration
> > for other thread that CPU fault to migrate.
> >
> > I am looking into how i can change migration_entry_wait() not to refcount
> > pages. Let me know if the attached patch helps.
> >
> > Thank you
> > Jérôme
>
> Hi Jerome,
>
> Thanks for the update.
>
> Unfortunately, the patch does not help. I just applied it and recompiled the
> kernel. Please find attached a new kernel log and an app log.
>

What are the symptoms ? The program just stop making any progress and you
trigger a sysrequest to dump current states of each threads ? In this
log i don't see migration_entry_wait() anymore but it seems to be waiting
on page lock so there might be 2 issues here.

Jérôme

\
 
 \ /
  Last update: 2017-07-11 20:50    [W:0.146 / U:0.192 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site