linux-kernel - Re: [PATCH v16 15/22] mm/compaction: do page isolation first in compaction

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Message-ID: <dd0a75b5-c8b2-8b66-79b9-0f6ce259e227@linux.alibaba.com>
Date:   Sun, 19 Jul 2020 11:59:36 +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>
Subject: Re: [PATCH v16 15/22] mm/compaction: do page isolation first in
 compaction



在 2020/7/18 上午12:09, Alexander Duyck 写道:
>>> I wonder if it wouldn't make sense to combine these two atomic ops
>>> with tests and the put_page into a single inline function? Then it
>>> could be possible to just do one check and if succeeds you do the
>>> block of code below, otherwise you just fall-through into the -EBUSY
>>> case.
>>>
>> Uh, since get_page changes page->_refcount, TestClearPageLRU changes page->flags,
>> So I don't know how to combine them, could you make it more clear with code?
> Actually it is pretty straight forward. Something like this:
> static inline bool get_page_unless_zero_or_nonlru(struct page *page)
> {
>     if (get_page_unless_zero(page)) {
>         if (TestClearPageLRU(page))
>             return true;
>         put_page(page);
>     }
>     return false;
> }
> 
> You can then add comments as necessary. The general idea is you are
> having to do this in two different spots anyway so why not combine the
> logic? Although it does assume you can change the ordering of the
> other test above.


It doesn't look different with original code, does it?

Thanks
Alex