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

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Message-ID: <432180fd-2faf-af37-7d99-4e24ab263d50@morey-chaisemartin.com>
Date:	Thu, 12 May 2016 08:07:59 +0200
From:	Nicolas Morey-Chaisemartin <devel@...ey-chaisemartin.com>
To:	Jerome Glisse <j.glisse@...il.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?



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.

Nicolas