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Subject: Re: [PATCH v21 18/19] mm/lru: introduce the relock_page_lruvec
 function
To:     Alex Shi <alex.shi@linux.alibaba.com>, akpm@linux-foundation.org,
        mgorman@techsingularity.net, tj@kernel.org, hughd@google.com,
        khlebnikov@yandex-team.ru, daniel.m.jordan@oracle.com,
        willy@infradead.org, hannes@cmpxchg.org, lkp@intel.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        cgroups@vger.kernel.org, shakeelb@google.com,
        iamjoonsoo.kim@lge.com, richard.weiyang@gmail.com,
        kirill@shutemov.name, alexander.duyck@gmail.com,
        rong.a.chen@intel.com, mhocko@suse.com, vdavydov.dev@gmail.com,
        shy828301@gmail.com
Cc:     Alexander Duyck <alexander.h.duyck@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>
References: <1604566549-62481-1-git-send-email-alex.shi@linux.alibaba.com>
 <1604566549-62481-19-git-send-email-alex.shi@linux.alibaba.com>
From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <5bd37d82-6a46-84eb-7110-411bc5e6515c@suse.cz>
Date:   Thu, 12 Nov 2020 13:31:04 +0100
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On 11/5/20 9:55 AM, Alex Shi wrote:
> From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> 
> Use this new function to replace repeated same code, no func change.
> 
> When testing for relock we can avoid the need for RCU locking if we simply
> compare the page pgdat and memcg pointers versus those that the lruvec is
> holding. By doing this we can avoid the extra pointer walks and accesses of
> the memory cgroup.

Ah, clever. Seems to address my worry from previous patch (except the potential 
to improve documenting comments).

> In addition we can avoid the checks entirely if lruvec is currently NULL.
> 
> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
> Acked-by: Hugh Dickins <hughd@google.com>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: linux-kernel@vger.kernel.org
> Cc: cgroups@vger.kernel.org
> Cc: linux-mm@kvack.org