From: Barry Song <21cnbao@gmail.com>
To: lsf-pc@lists.linux-foundation.org
Cc: Linux-MM <linux-mm@kvack.org>
Subject: [LSF/MM/BPF TOPIC]mTHP reliable allocation and reclamation
Date: Fri, 10 May 2024 14:22:02 +1200 [thread overview]
Message-ID: <CAGsJ_4xgRpfp7yZ_=8mxkaLO=WNVzaeTkFTQYxr8zBLpzFmzzA@mail.gmail.com> (raw)
Hi,
I'd like to propose a session about the allocation and reclamation of
mTHP. This is related to Yu Zhao's
TAO[1] but not the same.
OPPO has implemented mTHP-like large folios across thousands of
genuine Android devices, utilizing
ARM64 CONT-PTE. However, we've encountered challenges:
- The allocation of mTHP isn't consistently reliable; even after
prolonged use, obtaining large folios
remains uncertain.
As an instance, following a few hours of operation, the likelihood
of successfully allocating large
folios on a phone may decrease to just 2%.
- Mixing large and small folios in the same LRU list can lead to
mutual blocking and unpredictable
latency during reclamation/allocation.
For instance, if you require large folios, the LRU list's tail could
be filled with small folios.
LRU(LF- large folio, SF- small folio):
LF - LF - LF - SF - SF - SF - SF - SF - SF -SF - SF - SF - SF - SF - SF - SF
You might end up reclaiming many small folios yet still struggle to
allocate large folios. Conversely,
the inverse scenario can occur when the LRU list's tail is populated
with large folios.
SF - SF - SF - LF - LF - LF - LF - LF - LF -LF - LF - LF - LF - LF - LF - LF
In OPPO's products, we allocate dedicated pageblocks solely for large
folios allocation, and we've
fine-tuned the LRU mechanism to support dual LRU—one for small folios
and another for large ones.
Dedicated page blocks offer a fundamental guarantee of allocating
large folios. Additionally, segregating
small and large folios into two LRUs ensures that both can be
efficiently reclaimed for their respective
users' requests. However, while the implementation may lack aesthetic
appeal and is primarily tailored
for product purposes, it isn't fully upstreamable.
You can obtain the architectural diagram of OPPO's approach from link[2].
Therefore, my plan is to present:
- Introduce the architecture of OPPO's mTHP-like approach, which
encompasses additional optimizations
we've made to address swap fragmentation issues and improve swap
performance, such as dual-zRAM
and compression/decompression of large folios [3].
- Present OPPO's method of utilizing dedicated page blocks and a
dual-LRU system for mTHP.
- Share our observations from employing Yu Zhao's TAO on Pixel 6 phones.
- Discuss our future direction—are we leaning towards TAO or dedicated
page blocks? If we opt for page
blocks, how do we plan to resolve the LRU issue?
[1] https://lore.kernel.org/linux-mm/20240229183436.4110845-1-yuzhao@google.com/
[2] https://github.com/21cnbao/mTHP/blob/main/largefoliosarch.png
[3] https://lore.kernel.org/linux-mm/20240327214816.31191-1-21cnbao@gmail.com/
Thanks,
Barry
next reply other threads:[~2024-05-10 2:22 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-10 2:22 Barry Song [this message]
2024-05-10 2:31 ` [LSF/MM/BPF TOPIC]mTHP reliable allocation and reclamation Matthew Wilcox
2024-05-10 2:42 ` Barry Song
2024-05-10 14:25 ` [Lsf-pc] " Michal Hocko
2024-05-10 20:33 ` Yu Zhao
[not found] ` <CAGsJ_4w2zFBSabS97Pnnt59TjC3z48ZkwLoskXniq1puzK0O=Q@mail.gmail.com>
2024-05-15 10:21 ` Karim Manaouil
2024-05-15 13:50 ` Yang Shi
2024-05-15 18:14 ` Barry Song
2024-05-10 21:18 ` Yang Shi
2024-05-14 9:20 ` Barry Song
2024-05-15 13:49 ` Yang Shi
2024-05-15 19:25 ` Barry Song
2024-05-15 21:41 ` Yang Shi
2024-05-15 22:15 ` Barry Song
2024-05-15 23:41 ` Matthew Wilcox
2024-05-16 0:25 ` Barry Song
2024-05-16 3:19 ` Gao Xiang
2024-05-16 6:57 ` Barry Song
2024-05-16 7:07 ` Gao Xiang
2024-05-22 21:43 ` David Hildenbrand
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