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: Mon, 20 Jan 2020 20:58:09 +0800 [thread overview]
Message-ID: <9ee80b68-a78f-714a-c727-1f6d2b4f87ea@linux.alibaba.com> (raw)
In-Reply-To: <20200116215222.GA64230@cmpxchg.org>
在 2020/1/17 上午5:52, Johannes Weiner 写道:
> You simply cannot serialize on page->mem_cgroup->lruvec when
> page->mem_cgroup isn't stable. You need to serialize on the page
> itself, one way or another, to make this work.
>
>
> So here is a crazy idea that may be worth exploring:
>
> Right now, pgdat->lru_lock protects both PageLRU *and* the lruvec's
> linked list.
>
> Can we make PageLRU atomic and use it to stabilize the lru_lock
> instead, and then use the lru_lock only serialize list operations?
>
Hi Johannes,
I am trying to figure out the solution of atomic PageLRU, but is
blocked by the following sitations, when PageLRU and lru list was protected
together under lru_lock, the PageLRU could be a indicator if page on lru list
But now seems it can't be the indicator anymore.
Could you give more clues of stabilization usage of PageLRU?
__page_cache_release/release_pages/compaction __pagevec_lru_add
if (TestClearPageLRU(page)) if (!PageLRU())
lruvec_lock();
list_add();
lruvec_unlock();
SetPageLRU() //position 1
lock_page_lruvec_irqsave(page, &flags);
del_page_from_lru_list(page, lruvec, ..);
unlock_page_lruvec_irqrestore(lruvec, flags);
SetPageLRU() //position 2
Thanks a lot!
Alex
> I.e. in compaction, you'd do
>
> if (!TestClearPageLRU(page))
> goto isolate_fail;
> /*
> * We isolated the page's LRU state and thereby locked out all
> * other isolators, including cgroup page moving, page reclaim,
> * page freeing etc. That means page->mem_cgroup is now stable
> * and we can safely look up the correct lruvec and take the
> * page off its physical LRU list.
> */
> lruvec = mem_cgroup_page_lruvec(page);
> spin_lock_irq(&lruvec->lru_lock);
> del_page_from_lru_list(page, lruvec, page_lru(page));
>
> Putback would mostly remain the same (although you could take the
> PageLRU setting out of the list update locked section, as long as it's
> set after the page is physically linked):
>
> /* LRU isolation pins page->mem_cgroup */
> lruvec = mem_cgroup_page_lruvec(page)
> spin_lock_irq(&lruvec->lru_lock);
> add_page_to_lru_list(...);
> spin_unlock_irq(&lruvec->lru_lock);
>
> SetPageLRU(page);
>
> And you'd have to carefully review and rework other sites that rely on
> PageLRU: reclaim, __page_cache_release(), __activate_page() etc.
>
> Especially things like activate_page(), which used to only check
> PageLRU to shuffle the page on the LRU list would now have to briefly
> clear PageLRU and then set it again afterwards.
>
> However, aside from a bit more churn in those cases, and the
> unfortunate additional atomic operations, I currently can't think of a
> fundamental reason why this wouldn't work.
>
> Hugh, what do you think?
>
next prev parent reply other threads:[~2020-01-20 13:00 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 [this message]
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
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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