From: Zi Yan <ziy@nvidia.com>
To: Huang Ying <ying.huang@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Yang Shi <shy828301@gmail.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Oscar Salvador <osalvador@suse.de>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [RFC 0/6] migrate_pages(): batch TLB flushing
Date: Wed, 21 Sep 2022 11:47:38 -0400 [thread overview]
Message-ID: <FE41BDA8-F7EC-4FBC-9647-A5A835CDECB0@nvidia.com> (raw)
In-Reply-To: <20220921060616.73086-1-ying.huang@intel.com>
[-- Attachment #1: Type: text/plain, Size: 2577 bytes --]
On 21 Sep 2022, at 2:06, Huang Ying wrote:
> From: "Huang, Ying" <ying.huang@intel.com>
>
> Now, migrate_pages() migrate pages one by one, like the fake code as
> follows,
>
> for each page
> unmap
> flush TLB
> copy
> restore map
>
> If multiple pages are passed to migrate_pages(), there are
> opportunities to batch the TLB flushing and copying. That is, we can
> change the code to something as follows,
>
> for each page
> unmap
> for each page
> flush TLB
> for each page
> copy
> for each page
> restore map
>
> The total number of TLB flushing IPI can be reduced considerably. And
> we may use some hardware accelerator such as DSA to accelerate the
> page copying.
>
> So in this patch, we refactor the migrate_pages() implementation and
> implement the TLB flushing batching. Base on this, hardware
> accelerated page copying can be implemented.
>
> If too many pages are passed to migrate_pages(), in the naive batched
> implementation, we may unmap too many pages at the same time. The
> possibility for a task to wait for the migrated pages to be mapped
> again increases. So the latency may be hurt. To deal with this
> issue, the max number of pages be unmapped in batch is restricted to
> no more than HPAGE_PMD_NR. That is, the influence is at the same
> level of THP migration.
>
> We use the following test to measure the performance impact of the
> patchset,
>
> On a 2-socket Intel server,
>
> - Run pmbench memory accessing benchmark
>
> - Run `migratepages` to migrate pages of pmbench between node 0 and
> node 1 back and forth.
>
> With the patch, the TLB flushing IPI reduces 99.1% during the test and
> the number of pages migrated successfully per second increases 291.7%.
Thank you for the patchset. Batching page migration will definitely
improve its throughput from my past experiments[1] and starting with
TLB flushing is a good first step.
BTW, what is the rationality behind the increased page migration
success rate per second?
>
> This patchset is based on v6.0-rc5 and the following patchset,
>
> [PATCH -V3 0/8] migrate_pages(): fix several bugs in error path
> https://lore.kernel.org/lkml/20220817081408.513338-1-ying.huang@intel.com/
>
> The migrate_pages() related code is converting to folio now. So this
> patchset cannot apply recent akpm/mm-unstable branch. This patchset
> is used to check the basic idea. If it is OK, I will rebase the
> patchset on top of folio changes.
>
> Best Regards,
> Huang, Ying
[1] https://lwn.net/Articles/784925/
--
Best Regards,
Yan, Zi
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next prev parent reply other threads:[~2022-09-21 15:49 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 6:06 [RFC 0/6] migrate_pages(): batch TLB flushing Huang Ying
2022-09-21 6:06 ` [RFC 1/6] mm/migrate_pages: separate huge page and normal pages migration Huang Ying
2022-09-21 15:55 ` Zi Yan
2022-09-22 1:14 ` Huang, Ying
2022-09-22 6:03 ` Baolin Wang
2022-09-22 6:22 ` Huang, Ying
2022-09-21 6:06 ` [RFC 2/6] mm/migrate_pages: split unmap_and_move() to _unmap() and _move() Huang Ying
2022-09-21 16:08 ` Zi Yan
2022-09-22 1:15 ` Huang, Ying
2022-09-22 6:36 ` Baolin Wang
2022-09-26 9:28 ` Alistair Popple
2022-09-26 18:06 ` Yang Shi
2022-09-27 0:02 ` Alistair Popple
2022-09-27 1:51 ` Huang, Ying
2022-09-27 20:34 ` John Hubbard
2022-09-27 20:57 ` Yang Shi
2022-09-28 0:59 ` Alistair Popple
2022-09-28 1:41 ` Huang, Ying
2022-09-28 1:44 ` John Hubbard
2022-09-28 1:49 ` Yang Shi
2022-09-28 1:56 ` John Hubbard
2022-09-28 2:14 ` Yang Shi
2022-09-28 2:57 ` John Hubbard
2022-09-28 3:25 ` Yang Shi
2022-09-28 3:39 ` Yang Shi
2022-09-27 20:56 ` Yang Shi
2022-09-27 20:54 ` Yang Shi
2022-09-21 6:06 ` [RFC 3/6] mm/migrate_pages: restrict number of pages to migrate in batch Huang Ying
2022-09-21 16:10 ` Zi Yan
2022-09-21 16:15 ` Zi Yan
2022-09-22 1:15 ` Huang, Ying
2022-09-21 6:06 ` [RFC 4/6] mm/migrate_pages: batch _unmap and _move Huang Ying
2022-09-21 6:06 ` [RFC 5/6] mm/migrate_pages: share more code between " Huang Ying
2022-09-21 6:06 ` [RFC 6/6] mm/migrate_pages: batch flushing TLB Huang Ying
2022-09-21 15:47 ` Zi Yan [this message]
2022-09-22 1:45 ` [RFC 0/6] migrate_pages(): batch TLB flushing Huang, Ying
2022-09-22 3:47 ` haoxin
2022-09-22 4:36 ` Huang, Ying
2022-09-22 12:50 ` Bharata B Rao
2022-09-23 7:52 ` Huang, Ying
2022-09-27 10:46 ` Bharata B Rao
2022-09-28 1:46 ` Huang, Ying
2022-09-26 9:11 ` Alistair Popple
2022-09-27 11:21 ` haoxin
2022-09-28 2:01 ` Huang, Ying
2022-09-28 3:33 ` haoxin
2022-09-28 4:53 ` Huang, Ying
2022-11-01 14:49 ` Hesham Almatary
2022-11-02 3:14 ` Huang, Ying
2022-11-02 14:13 ` Hesham Almatary
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