linux-kernel - Re: [Question] Missing data after DMA read transfer

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Date:	Thu, 12 May 2016 11:36:32 +0200
From:	Jerome Glisse <j.glisse@...il.com>
To:	Nicolas Morey-Chaisemartin <devel@...ey-chaisemartin.com>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Andrea Arcangeli <aarcange@...hat.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [Question] Missing data after DMA read transfer - mm issue with
 transparent huge page?

On Thu, May 12, 2016 at 08:07:59AM +0200, Nicolas Morey-Chaisemartin wrote:
> 
> 
> Le 05/11/2016 à 04:51 PM, Jerome Glisse a écrit :
> > On Wed, May 11, 2016 at 01:15:54PM +0200, Nicolas Morey Chaisemartin wrote:
> >>
> >> Le 05/10/2016 à 12:01 PM, Jerome Glisse a écrit :
> >>> On Tue, May 10, 2016 at 09:04:36AM +0200, Nicolas Morey Chaisemartin wrote:
> >>>> Le 05/03/2016 à 12:11 PM, Jerome Glisse a écrit :
> >>>>> On Mon, May 02, 2016 at 09:04:02PM -0700, Hugh Dickins wrote:
> >>>>>> On Fri, 29 Apr 2016, Nicolas Morey Chaisemartin wrote:
> >> [...]
> >>>> Hi,
> >>>>
> >>>> I backported the patch to 3.10 (had to copy paste pmd_protnone defitinition from 4.5) and it's working !
> >>>> I'll open a ticket in Redhat tracker to try and get this fixed in RHEL7.
> >>>>
> >>>> I have a dumb question though: how can we end up in numa/misplaced memory code on a single socket system?
> >>>>
> >>> This patch is not a fix, do you see bug message in kernel log ? Because if
> >>> you do that it means we have a bigger issue.
> >>>
> >>> You did not answer one of my previous question, do you set get_user_pages
> >>> with write = 1 as a paremeter ?
> >>>
> >>> Also it would be a lot easier if you were testing with lastest 4.6 or 4.5
> >>> not RHEL kernel as they are far appart and what might looks like same issue
> >>> on both might be totaly different bugs.
> >>>
> >>> If you only really care about RHEL kernel then open a bug with Red Hat and
> >>> you can add me in bug-cc <jglisse@...hat.com>
> >>>
> >>> Cheers,
> >>> Jérôme
> >> I finally managed to get a proper setup.
> >> I build a vanilla 4.5 kernel from git tree using the Centos7 config, my test fails as usual.
> >> I applied your patch, rebuild => still fails and no new messages in dmesg.
> >>
> >> Now that I don't have to go through the RPM repackaging, I can try out things much quicker if you have any ideas.
> >>
> > Still an issue if you boot with transparent_hugepage=never ?
> >
> > Also to simplify investigation force write to 1 all the time no matter what.
> >
> > Cheers,
> > Jérôme
> 
> With transparent_hugepage=never I can't see the bug anymore.
> 

Can you test https://patchwork.kernel.org/patch/9061351/ with 4.5
(does not apply to 3.10) and without transparent_hugepage=never

Jérôme