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From: Balbir Singh <bsingharora@gmail.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Alex Shi <alex.shi@linux.alibaba.com>,
	Joonsoo Kim <js1304@gmail.com>,
	Shakeel Butt <shakeelb@google.com>,
	Hugh Dickins <hughd@google.com>, Michal Hocko <mhocko@suse.com>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Roman Gushchin <guro@fb.com>,
	linux-mm@kvack.org, cgroups@vger.kernel.org,
	linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 00/19 V2] mm: memcontrol: charge swapin pages on instantiation
Date: Wed, 13 May 2020 11:30:32 +0000	[thread overview]
Message-ID: <20200513113032.GA93568@dev-dsk-sblbir-1c-a524888b.ap-northeast-1.amazon.com> (raw)
In-Reply-To: <20200508183105.225460-1-hannes@cmpxchg.org>

On Fri, May 08, 2020 at 02:30:47PM -0400, Johannes Weiner wrote:
> This patch series reworks memcg to charge swapin pages directly at
> swapin time, rather than at fault time, which may be much later, or
> not happen at all.
> 
> Changes in version 2:
> - prevent double charges on pre-allocated hugepages in khugepaged
> - leave shmem swapcache when charging fails to avoid double IO (Joonsoo)
> - fix temporary accounting bug by switching rmap<->commit (Joonsoo)
> - fix double swap charge bug in cgroup1/cgroup2 code gating
> - simplify swapin error checking (Joonsoo)
> - mm: memcontrol: document the new swap control behavior (Alex)
> - review tags
> 
> The delayed swapin charging scheme we have right now causes problems:
> 
> - Alex's per-cgroup lru_lock patches rely on pages that have been
>   isolated from the LRU to have a stable page->mem_cgroup; otherwise
>   the lock may change underneath him. Swapcache pages are charged only
>   after they are added to the LRU, and charging doesn't follow the LRU
>   isolation protocol.
> 
> - Joonsoo's anon workingset patches need a suitable LRU at the time
>   the page enters the swap cache and displaces the non-resident
>   info. But the correct LRU is only available after charging.
> 
> - It's a containment hole / DoS vector. Users can trigger arbitrarily
>   large swap readahead using MADV_WILLNEED. The memory is never
>   charged unless somebody actually touches it.
> 
> - It complicates the page->mem_cgroup stabilization rules
> 
> In order to charge pages directly at swapin time, the memcg code base
> needs to be prepared, and several overdue cleanups become a necessity:
> 
> To charge pages at swapin time, we need to always have cgroup
> ownership tracking of swap records. We also cannot rely on
> page->mapping to tell apart page types at charge time, because that's
> only set up during a page fault.
> 
> To eliminate the page->mapping dependency, memcg needs to ditch its
> private page type counters (MEMCG_CACHE, MEMCG_RSS, NR_SHMEM) in favor
> of the generic vmstat counters and accounting sites, such as
> NR_FILE_PAGES, NR_ANON_MAPPED etc.

Could you elaborate on what this means and the implications of this on
user space programs?

> 
> To switch to generic vmstat counters, the charge sequence must be
> adjusted such that page->mem_cgroup is set up by the time these
> counters are modified.
> 
> The series is structured as follows:
> 
> 1. Bug fixes
> 2. Decoupling charging from rmap
> 3. Swap controller integration into memcg
> 4. Direct swapin charging
>

Thanks,
Balbir Singh. 


  parent reply	other threads:[~2020-05-13 11:30 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-08 18:30 Johannes Weiner
2020-05-08 18:30 ` [PATCH 01/19] mm: fix NUMA node file count error in replace_page_cache() Johannes Weiner
2020-05-18 11:18   ` Balbir Singh
2020-05-08 18:30 ` [PATCH 02/19] mm: memcontrol: fix stat-corrupting race in charge moving Johannes Weiner
2020-05-08 18:30 ` [PATCH 03/19] mm: memcontrol: drop @compound parameter from memcg charging API Johannes Weiner
2020-05-08 18:30 ` [PATCH 04/19] mm: memcontrol: move out cgroup swaprate throttling Johannes Weiner
2020-05-08 18:30 ` [PATCH 05/19] mm: memcontrol: convert page cache to a new mem_cgroup_charge() API Johannes Weiner
2020-06-10 16:09   ` Michal Hocko
2020-05-08 18:30 ` [PATCH 06/19] mm: memcontrol: prepare uncharging for removal of private page type counters Johannes Weiner
2020-05-08 18:30 ` [PATCH 07/19] mm: memcontrol: prepare move_account " Johannes Weiner
2020-05-08 18:30 ` [PATCH 08/19] mm: memcontrol: prepare cgroup vmstat infrastructure for native anon counters Johannes Weiner
2020-05-08 18:30 ` [PATCH 09/19] mm: memcontrol: switch to native NR_FILE_PAGES and NR_SHMEM counters Johannes Weiner
2020-06-10 16:42   ` Michal Hocko
2020-05-08 18:30 ` [PATCH 10/19] mm: memcontrol: switch to native NR_ANON_MAPPED counter Johannes Weiner
2020-05-08 18:30 ` [PATCH 11/19] mm: memcontrol: switch to native NR_ANON_THPS counter Johannes Weiner
2020-05-08 18:30 ` [PATCH 12/19] mm: memcontrol: convert anon and file-thp to new mem_cgroup_charge() API Johannes Weiner
2020-05-12 14:38   ` Qian Cai
2020-05-12 17:11     ` Qian Cai
2020-05-12 21:58     ` Johannes Weiner
2020-05-12 23:58       ` Qian Cai
2020-05-08 18:31 ` [PATCH 13/19] mm: memcontrol: drop unused try/commit/cancel charge API Johannes Weiner
2020-06-22 17:06   ` Ben Widawsky
2020-05-08 18:31 ` [PATCH 14/19] mm: memcontrol: prepare swap controller setup for integration Johannes Weiner
2020-05-08 18:31 ` [PATCH 15/19] mm: memcontrol: make swap tracking an integral part of memory control Johannes Weiner
2020-05-08 18:31 ` [PATCH 16/19] mm: memcontrol: charge swapin pages on instantiation Johannes Weiner
2020-06-11  9:35   ` Michal Hocko
2020-06-17  8:49     ` [PATCH for 5.8] mm: do_swap_page fix up the error code instantiation Michal Hocko
2020-06-17  9:02       ` Michal Hocko
2020-06-17 13:34         ` Johannes Weiner
2020-05-08 18:31 ` [PATCH 17/19] mm: memcontrol: document the new swap control behavior Johannes Weiner
2020-05-08 18:31 ` [PATCH 18/19] mm: memcontrol: delete unused lrucare handling Johannes Weiner
2020-05-08 18:31 ` [PATCH 19/19] mm: memcontrol: update page->mem_cgroup stability rules Johannes Weiner
2020-06-11  9:40   ` Michal Hocko
2020-05-13 11:30 ` Balbir Singh [this message]
2020-05-13 12:35   ` [PATCH 00/19 V2] mm: memcontrol: charge swapin pages on instantiation Johannes Weiner
2020-05-14 11:04     ` Balbir Singh

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