linux-kernel - Re: [PATCH v7 06/12] mm: multigenerational LRU: exploit locality in rmap

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Date:   Tue, 8 Feb 2022 01:40:49 -0700
From:   Yu Zhao <yuzhao@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...nel.org>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Aneesh Kumar <aneesh.kumar@...ux.ibm.com>,
        Barry Song <21cnbao@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Hillf Danton <hdanton@...a.com>, Jens Axboe <axboe@...nel.dk>,
        Jesse Barnes <jsbarnes@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Michael Larabel <Michael@...haellarabel.com>,
        Mike Rapoport <rppt@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Will Deacon <will@...nel.org>,
        Ying Huang <ying.huang@...el.com>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        page-reclaim@...gle.com, x86@...nel.org,
        Brian Geffon <bgeffon@...gle.com>,
        Jan Alexander Steffens <heftig@...hlinux.org>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Steven Barrett <steven@...uorix.net>,
        Suleiman Souhlal <suleiman@...gle.com>,
        Daniel Byrne <djbyrne@....edu>,
        Donald Carr <d@...os-reins.com>,
        Holger Hoffstätte 
        <holger@...lied-asynchrony.com>,
        Konstantin Kharlamov <Hi-Angel@...dex.ru>,
        Shuang Zhai <szhai2@...rochester.edu>,
        Sofia Trinh <sofia.trinh@....works>
Subject: Re: [PATCH v7 06/12] mm: multigenerational LRU: exploit locality in
 rmap

On Tue, Feb 08, 2022 at 01:18:56AM -0700, Yu Zhao wrote:

<snipped>

> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index b72d75141e12..51c9bc8e965d 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -436,6 +436,7 @@ static inline struct obj_cgroup *__folio_objcg(struct folio *folio)
>   * - LRU isolation
>   * - lock_page_memcg()
>   * - exclusive reference
> + * - mem_cgroup_trylock_pages()
>   *
>   * For a kmem folio a caller should hold an rcu read lock to protect memcg
>   * associated with a kmem folio from being released.
> @@ -497,6 +498,7 @@ static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio)
>   * - LRU isolation
>   * - lock_page_memcg()
>   * - exclusive reference
> + * - mem_cgroup_trylock_pages()
>   *
>   * For a kmem page a caller should hold an rcu read lock to protect memcg
>   * associated with a kmem page from being released.
> @@ -934,6 +936,23 @@ void unlock_page_memcg(struct page *page);
>  
>  void __mod_memcg_state(struct mem_cgroup *memcg, int idx, int val);
>  
> +/* try to stablize folio_memcg() for all the pages in a memcg */
> +static inline bool mem_cgroup_trylock_pages(struct mem_cgroup *memcg)
> +{
> +	rcu_read_lock();
> +
> +	if (mem_cgroup_disabled() || !atomic_read(&memcg->moving_account))
> +		return true;
> +
> +	rcu_read_unlock();
> +	return false;
> +}
> +
> +static inline void mem_cgroup_unlock_pages(void)
> +{
> +	rcu_read_unlock();
> +}

Replaced the open-coded folio_memcg() lock with a new function
mem_cgroup_trylock_pages() as requested here:
https://lore.kernel.org/linux-mm/YeATr%2F%2FU6XD87fWF@dhcp22.suse.cz/

<snipped>