From: Bob Liu <lliubbo@gmail.com>
To: Jerome Glisse <jglisse@redhat.com>
Cc: Bob Liu <liubo95@huawei.com>,
Dan Williams <dan.j.williams@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>, John Hubbard <jhubbard@nvidia.com>,
David Nellans <dnellans@nvidia.com>,
Balbir Singh <bsingharora@gmail.com>,
Michal Hocko <mhocko@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 0/6] Cache coherent device memory (CDM) with HMM v5
Date: Wed, 11 Oct 2017 21:15:57 +0800 [thread overview]
Message-ID: <CAA_GA1dhrs7n-ewZmW4bNtouK8rKnF1_TWv0z+2vrUgJjWpnMQ@mail.gmail.com> (raw)
In-Reply-To: <20170930224927.GC6775@redhat.com>
On Sun, Oct 1, 2017 at 6:49 AM, Jerome Glisse <jglisse@redhat.com> wrote:
> On Sat, Sep 30, 2017 at 10:57:38AM +0800, Bob Liu wrote:
>> On 2017/9/27 0:16, Jerome Glisse wrote:
>> > On Tue, Sep 26, 2017 at 05:56:26PM +0800, Bob Liu wrote:
>> >> On Tue, Sep 12, 2017 at 7:36 AM, Jerome Glisse <jglisse@redhat.com> wrote:
>> >>> On Sun, Sep 10, 2017 at 07:22:58AM +0800, Bob Liu wrote:
>> >>>> On Wed, Sep 6, 2017 at 3:36 AM, Jerome Glisse <jglisse@redhat.com> wrote:
>> >>>>> On Thu, Jul 20, 2017 at 08:48:20PM -0700, Dan Williams wrote:
>> >>>>>> On Thu, Jul 20, 2017 at 6:41 PM, Jerome Glisse <jglisse@redhat.com> wrote:
>> [...]
>> >>>>> So i pushed a branch with WIP for nouveau to use HMM:
>> >>>>>
>> >>>>> https://cgit.freedesktop.org/~glisse/linux/log/?h=hmm-nouveau
>> >>>>>
>> >>>>
>> >>>> Nice to see that.
>> >>>> Btw, do you have any plan for a CDM-HMM driver? CPU can write to
>> >>>> Device memory directly without extra copy.
>> >>>
>> >>> Yes nouveau CDM support on PPC (which is the only CDM platform commercialy
>> >>> available today) is on the TODO list. Note that the driver changes for CDM
>> >>> are minimal (probably less than 100 lines of code). From the driver point
>> >>> of view this is memory and it doesn't matter if it is CDM or not.
>> >>>
>> >>
>> >> It seems have to migrate/copy memory between system-memory and
>> >> device-memory even in HMM-CDM solution.
>> >> Because device-memory is not added into buddy system, the page fault
>> >> for normal malloc() always allocate memory from system-memory!!
>> >> If the device then access the same virtual address, the data is copied
>> >> to device-memory.
>> >>
>> >> Correct me if I misunderstand something.
>> >> @Balbir, how do you plan to make zero-copy work if using HMM-CDM?
>> >
>> > Device can access system memory so copy to device is _not_ mandatory. Copying
>> > data to device is for performance only ie the device driver take hint from
>> > userspace and monitor device activity to decide which memory should be migrated
>> > to device memory to maximize performance.
>> >
>> > Moreover in some previous version of the HMM patchset we had an helper that
>>
>> Could you point in which version? I'd like to have a look.
>
> I will need to dig in.
>
Thank you.
>>
>> > allowed to directly allocate device memory on device page fault. I intend to
>> > post this helper again. With that helper you can have zero copy when device
>> > is the first to access the memory.
>> >
>> > Plan is to get what we have today work properly with the open source driver
>> > and make it perform well. Once we get some experience with real workload we
>> > might look into allowing CPU page fault to be directed to device memory but
>> > at this time i don't think we need this.
>> >
>>
>> For us, we need this feature that CPU page fault can be direct to device memory.
>> So that don't need to copy data from system memory to device memory.
>> Do you have any suggestion on the implementation? I'll try to make a prototype patch.
>
> Why do you need that ? What is the device and what are the requirement ?
>
You may think it as a CCIX device or CAPI device.
The requirement is eliminate any extra copy.
A typical usecase/requirement is malloc() and madvise() allocate from
device memory, then CPU write data to device memory directly and
trigger device to read the data/do calculation.
--
Regards,
--Bob
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next prev parent reply other threads:[~2017-10-11 13:16 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-13 21:15 [PATCH 0/6] Cache coherent device memory (CDM) with HMM v5 Jérôme Glisse
2017-07-13 21:15 ` [PATCH 1/6] mm/zone-device: rename DEVICE_PUBLIC to DEVICE_HOST Jérôme Glisse
2017-07-17 9:09 ` Balbir Singh
2017-07-13 21:15 ` [PATCH 2/6] mm/device-public-memory: device memory cache coherent with CPU v4 Jérôme Glisse
2017-07-13 23:01 ` Balbir Singh
2017-07-13 21:15 ` [PATCH 3/6] mm/hmm: add new helper to hotplug CDM memory region v3 Jérôme Glisse
2017-07-13 21:15 ` [PATCH 4/6] mm/memcontrol: allow to uncharge page without using page->lru field Jérôme Glisse
2017-07-17 9:10 ` Balbir Singh
2017-07-13 21:15 ` [PATCH 5/6] mm/memcontrol: support MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_PUBLIC v3 Jérôme Glisse
2017-07-17 9:15 ` Balbir Singh
2017-07-13 21:15 ` [PATCH 6/6] mm/hmm: documents how device memory is accounted in rss and memcg Jérôme Glisse
2017-07-14 13:26 ` Michal Hocko
2017-07-18 3:26 ` [PATCH 0/6] Cache coherent device memory (CDM) with HMM v5 Bob Liu
2017-07-18 15:38 ` Jerome Glisse
2017-07-19 1:46 ` Bob Liu
2017-07-19 2:25 ` Jerome Glisse
2017-07-19 9:09 ` Bob Liu
2017-07-20 15:03 ` Jerome Glisse
2017-07-21 1:15 ` Bob Liu
2017-07-21 1:41 ` Jerome Glisse
2017-07-21 2:10 ` Bob Liu
2017-07-21 12:01 ` Bob Liu
2017-07-21 15:21 ` Jerome Glisse
2017-07-21 3:48 ` Dan Williams
2017-07-21 15:22 ` Jerome Glisse
2017-09-05 19:36 ` Jerome Glisse
2017-09-09 23:22 ` Bob Liu
2017-09-11 23:36 ` Jerome Glisse
2017-09-12 1:02 ` Bob Liu
2017-09-12 16:17 ` Jerome Glisse
2017-09-26 9:56 ` Bob Liu
2017-09-26 16:16 ` Jerome Glisse
2017-09-30 2:57 ` Bob Liu
2017-09-30 22:49 ` Jerome Glisse
2017-10-11 13:15 ` Bob Liu [this message]
2017-10-12 15:37 ` Jerome Glisse
2017-11-16 2:10 ` chet l
2017-11-16 2:44 ` Jerome Glisse
2017-11-16 3:23 ` chetan L
2017-11-16 3:29 ` chetan L
2017-11-16 21:29 ` Jerome Glisse
2017-11-16 22:41 ` chetan L
2017-11-16 23:11 ` Jerome Glisse
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