From: Jerome Glisse <jglisse@redhat.com>
To: Dave Chinner <david@fromorbit.com>
Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [LSF/MM TOPIC] Un-addressable device memory and block/fs implications
Date: Tue, 13 Dec 2016 15:31:13 -0500 [thread overview]
Message-ID: <20161213203112.GE2305@redhat.com> (raw)
In-Reply-To: <20161213201515.GB4326@dastard>
On Wed, Dec 14, 2016 at 07:15:15AM +1100, Dave Chinner wrote:
> On Tue, Dec 13, 2016 at 01:15:11PM -0500, Jerome Glisse wrote:
> > I would like to discuss un-addressable device memory in the context of
> > filesystem and block device. Specificaly how to handle write-back, read,
> > ... when a filesystem page is migrated to device memory that CPU can not
> > access.
>
> You mean pmem that is DAX-capable that suddenly, without warning,
> becomes non-DAX capable?
>
> If you are not talking about pmem and DAX, then exactly what does
> "when a filesystem page is migrated to device memory that CPU can
> not access" mean? What "filesystem page" are we talking about that
> can get migrated from main RAM to something the CPU can't access?
I am talking about GPU, FPGA, ... any PCIE device that have fast on
board memory that can not be expose transparently to the CPU. I am
reusing ZONE_DEVICE for this, you can see HMM patchset on linux-mm
https://lwn.net/Articles/706856/
So in my case i am only considering non DAX/PMEM filesystem ie any
"regular" filesystem back by a "regular" block device. I want to be
able to migrate mmaped area of such filesystem to device memory while
the device is actively using that memory.
>From kernel point of view such memory is almost like any other, it
has a struct page and most of the mm code is non the wiser, nor need
to be about it. CPU access trigger a migration back to regular CPU
accessible page.
But for thing like writeback i want to be able to do writeback with-
out having to migrate page back first. So that data can stay on the
device while writeback is happening.
Jerome
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next prev parent reply other threads:[~2016-12-13 20:31 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-13 18:15 [LSF/MM TOPIC] Un-addressable device memory and block/fs implications Jerome Glisse
2016-12-13 18:20 ` James Bottomley
2016-12-13 18:55 ` Jerome Glisse
2016-12-13 20:01 ` James Bottomley
2016-12-13 20:22 ` Jerome Glisse
2016-12-13 20:27 ` Dave Hansen
2016-12-13 20:15 ` Dave Chinner
2016-12-13 20:31 ` Jerome Glisse [this message]
2016-12-13 21:10 ` Dave Chinner
2016-12-13 21:24 ` Jerome Glisse
2016-12-13 22:08 ` Dave Hansen
2016-12-13 23:02 ` Jerome Glisse
2016-12-13 22:13 ` Dave Chinner
2016-12-13 22:55 ` Jerome Glisse
2016-12-14 0:14 ` Dave Chinner
2016-12-14 1:07 ` Jerome Glisse
2016-12-14 4:23 ` Dave Chinner
2016-12-14 16:35 ` Jerome Glisse
2016-12-14 11:13 ` [Lsf-pc] " Jan Kara
2016-12-14 17:15 ` Jerome Glisse
2016-12-15 16:19 ` Jan Kara
2016-12-15 19:14 ` Jerome Glisse
2016-12-16 8:14 ` Jan Kara
2016-12-16 3:10 ` Aneesh Kumar K.V
2016-12-19 8:46 ` Jan Kara
2016-12-19 17:00 ` Aneesh Kumar K.V
2016-12-14 3:55 ` Balbir Singh
2016-12-16 3:14 ` [LSF/MM ATTEND] " Aneesh Kumar K.V
2017-01-16 12:04 ` Anshuman Khandual
2017-01-16 23:15 ` John Hubbard
2017-01-18 11:00 ` [Lsf-pc] " Jan Kara
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