linux-kernel - Re: [PATCH v17 14/21] mm/compaction: do page isolation first in compaction

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Message-ID: <8dbd004e-8eba-f1ec-a5eb-5dc551978936@linux.alibaba.com>
Date:   Mon, 10 Aug 2020 21:10:17 +0800
From:   Alex Shi <alex.shi@...ux.alibaba.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Tejun Heo <tj@...nel.org>, Hugh Dickins <hughd@...gle.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Matthew Wilcox <willy@...radead.org>,
        Johannes Weiner <hannes@...xchg.org>,
        kbuild test robot <lkp@...el.com>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, cgroups@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Wei Yang <richard.weiyang@...il.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Rong Chen <rong.a.chen@...el.com>
Subject: Re: [PATCH v17 14/21] mm/compaction: do page isolation first in
 compaction



在 2020/8/7 下午10:51, Alexander Duyck 写道:
> I wonder if this entire section shouldn't be restructured. This is the
> only spot I can see where we are resetting the LRU flag instead of
> pulling the page from the LRU list with the lock held. Looking over
> the code it seems like something like that should be possible. I am
> not sure the LRU lock is really protecting us in either the
> PageCompound check nor the skip bits. It seems like holding a
> reference on the page should prevent it from switching between
> compound or not, and the skip bits are per pageblock with the LRU bits
> being per node/memcg which I would think implies that we could have
> multiple LRU locks that could apply to a single skip bit.

Hi Alexander,

I don't find problem yet on compound or skip bit usage. Would you clarify the
issue do you concerned? 

Thanks!