From: haoxin <xhao@linux.alibaba.com>
To: Huang Ying <ying.huang@intel.com>, linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Zi Yan <ziy@nvidia.com>, Yang Shi <shy828301@gmail.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Oscar Salvador <osalvador@suse.de>,
Matthew Wilcox <willy@infradead.org>,
yangyicong@hisilicon.com, v-songbaohua@oppo.com,
21cnbao@gmail.com
Subject: Re: [RFC 0/6] migrate_pages(): batch TLB flushing
Date: Tue, 27 Sep 2022 19:21:08 +0800 [thread overview]
Message-ID: <393d6318-aa38-01ed-6ad8-f9eac89bf0fc@linux.alibaba.com> (raw)
In-Reply-To: <20220921060616.73086-1-ying.huang@intel.com>
Hi, Huang
在 2022/9/21 下午2:06, Huang Ying 写道:
> 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.
>
As the pmbench can not run on arm64 machine, so i use lmbench instead.
I test case like this: (i am not sure whether it is reasonable, but it seems worked)
./bw_mem -N10000 10000m rd &
time migratepages pid node0 node1
o/patch w/patch
real 0m0.035s real 0m0.024s
user 0m0.000s user 0m0.000s
sys 0m0.035s sys 0m0.024s
the migratepages time is reduced above 32%.
But there has a problem, i see the batch flush is called by
migrate_pages_batch
try_to_unmap_flush
arch_tlbbatch_flush(&tlb_ubc->arch); // there batch flush really work.
But in arm64, the arch_tlbbatch_flush are not supported, becasue it not support CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH yet.
So, the tlb batch flush means no any flush is did, it is a empty func.
Maybe this patch can help solve this problem.
https://lore.kernel.org/linux-arm-kernel/20220921084302.43631-1-yangyicong@huawei.com/T/
next prev parent reply other threads:[~2022-09-27 11:23 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 ` [RFC 0/6] migrate_pages(): batch TLB flushing Zi Yan
2022-09-22 1:45 ` 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 [this message]
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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