From: Alex Shi <alex.shi@linux.alibaba.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, akpm@linux-foundation.org,
mgorman@techsingularity.net, tj@kernel.org, hughd@google.com,
khlebnikov@yandex-team.ru, daniel.m.jordan@oracle.com,
yang.shi@linux.alibaba.com, willy@infradead.org,
shakeelb@google.com, "Michal Hocko" <mhocko@kernel.org>,
"Vladimir Davydov" <vdavydov.dev@gmail.com>,
"Roman Gushchin" <guro@fb.com>,
"Chris Down" <chris@chrisdown.name>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Vlastimil Babka" <vbabka@suse.cz>, "Qian Cai" <cai@lca.pw>,
"Andrey Ryabinin" <aryabinin@virtuozzo.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Andrea Arcangeli" <aarcange@redhat.com>,
"David Rientjes" <rientjes@google.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
swkhack <swkhack@gmail.com>,
"Potyra, Stefan" <Stefan.Potyra@elektrobit.com>,
"Mike Rapoport" <rppt@linux.vnet.ibm.com>,
"Stephen Rothwell" <sfr@canb.auug.org.au>,
"Colin Ian King" <colin.king@canonical.com>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Mauro Carvalho Chehab" <mchehab+samsung@kernel.org>,
"Peng Fan" <peng.fan@nxp.com>,
"Nikolay Borisov" <nborisov@suse.com>,
"Ira Weiny" <ira.weiny@intel.com>,
"Kirill Tkhai" <ktkhai@virtuozzo.com>,
"Yafang Shao" <laoar.shao@gmail.com>
Subject: Re: [PATCH v8 03/10] mm/lru: replace pgdat lru_lock with lruvec lock
Date: Wed, 15 Apr 2020 21:42:26 +0800 [thread overview]
Message-ID: <54af0662-cbb4-88c7-7eae-f969684025dd@linux.alibaba.com> (raw)
In-Reply-To: <20200414163114.GA136578@cmpxchg.org>
在 2020/4/15 上午12:31, Johannes Weiner 写道:
> On Tue, Apr 14, 2020 at 12:52:30PM +0800, Alex Shi wrote:
>> 在 2020/4/14 上午2:07, Johannes Weiner 写道:
>>> Plus, the overhead of tracking is tiny - 512k per G of swap (0.04%).
>>>
>>> Maybe we should just delete MEMCG_SWAP and unconditionally track swap
>>> entry ownership when the memory controller is enabled. I don't see a
>>> good reason not to, and it would simplify the entire swapin path, the
>>> LRU locking, and the page->mem_cgroup stabilization rules.
>>>
>>
>> Sorry for not follow you up, did you mean just remove the MEMCG_SWAP configuration
>> and keep the feature in default memcg?
>
> Yes.
>
>> That does can remove lrucare, but PageLRU lock scheme still fails since
>> we can not isolate the page during commit_charge, is that right?
>
> No, without lrucare the scheme works. Charges usually do:
>
> page->mem_cgroup = new;
> SetPageLRU(page);
>
> And so if you can TestClearPageLRU(), page->mem_cgroup is stable.
>
> lrucare charging is the exception: it changes page->mem_cgroup AFTER
> PageLRU has already been set, and even when it CANNOT acquire the
> PageLRU lock itself. It violates the rules.
>
> If we make MEMCG_SWAP mandatory, we always have cgroup records for
> swapped out pages. That means we can charge all swapin pages
> (incl. readahead pages) directly in __read_swap_cache_async(), before
> setting PageLRU on the new pages.
>
> Then we can delete lrucare.
>
> And then TestClearPageLRU() guarantees page->mem_cgroup is stable.
>
Hi Johannes,
Thanks a lot for point out!
Charging in __read_swap_cache_async would ask for 3 layers function arguments
pass, that would be a bit ugly. Compare to this, could we move out the
lru_cache add after commit_charge, like ksm copied pages?
That give a bit extra non lru list time, but the page just only be used only
after add_anon_rmap setting. Could it cause troubles?
I tried to track down the reason of lru_cache_add here, but no explanation
till first git kernel commit.
Thanks
Alex
next prev parent reply other threads:[~2020-04-15 13:43 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 3:04 [PATCH v8 00/10] per lruvec lru_lock for memcg Alex Shi
2020-01-16 3:05 ` [PATCH v8 01/10] mm/vmscan: remove unnecessary lruvec adding Alex Shi
2020-01-16 3:05 ` [PATCH v8 02/10] mm/memcg: fold lock_page_lru into commit_charge Alex Shi
2020-01-16 3:05 ` [PATCH v8 03/10] mm/lru: replace pgdat lru_lock with lruvec lock Alex Shi
2020-01-16 21:52 ` Johannes Weiner
2020-01-19 11:32 ` Alex Shi
2020-01-20 12:58 ` Alex Shi
2020-01-21 16:00 ` Johannes Weiner
2020-01-22 12:01 ` Alex Shi
2020-01-22 18:31 ` Johannes Weiner
2020-04-13 10:48 ` Alex Shi
2020-04-13 18:07 ` Johannes Weiner
2020-04-14 4:52 ` Alex Shi
2020-04-14 16:31 ` Johannes Weiner
2020-04-15 13:42 ` Alex Shi [this message]
2020-04-16 8:01 ` Alex Shi
2020-04-16 15:28 ` Johannes Weiner
2020-04-16 17:47 ` Shakeel Butt
2020-04-17 13:18 ` Alex Shi
2020-04-17 14:39 ` Alex Shi
2020-04-14 8:19 ` Alex Shi
2020-04-14 16:36 ` Johannes Weiner
2020-01-16 3:05 ` [PATCH v8 04/10] mm/lru: introduce the relock_page_lruvec function Alex Shi
2020-01-16 3:05 ` [PATCH v8 05/10] mm/mlock: optimize munlock_pagevec by relocking Alex Shi
2020-01-16 3:05 ` [PATCH v8 06/10] mm/swap: only change the lru_lock iff page's lruvec is different Alex Shi
2020-01-16 3:05 ` [PATCH v8 07/10] mm/pgdat: remove pgdat lru_lock Alex Shi
2020-01-16 3:05 ` [PATCH v8 08/10] mm/lru: revise the comments of lru_lock Alex Shi
2020-01-16 3:05 ` [PATCH v8 09/10] mm/lru: add debug checking for page memcg moving Alex Shi
2020-01-16 3:05 ` [PATCH v8 10/10] mm/memcg: add debug checking in lock_page_memcg Alex Shi
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