linux-kernel - Re: [PATCH v3 3/7] mm/lru: replace pgdat lru

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Message-ID: <3f179d84-85e2-bace-2dbc-e77f73883c71@linux.alibaba.com>
Date:   Mon, 18 Nov 2019 20:23:12 +0800
From:   Alex Shi <alex.shi@...ux.alibaba.com>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Cgroups <cgroups@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        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>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Roman Gushchin <guro@...com>,
        Chris Down <chris@...isdown.name>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vlastimil Babka <vbabka@...e.cz>, Qian Cai <cai@....pw>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
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        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
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        Yafang Shao <laoar.shao@...il.com>
Subject: Re: [PATCH v3 3/7] mm/lru: replace pgdat lru_lock with lruvec lock



在 2019/11/16 下午3:03, Shakeel Butt 写道:
>> +reget_lruvec:
>> +               lruvec = mem_cgroup_page_lruvec(page, pgdat);
>> +
>>                 /* If we already hold the lock, we can skip some rechecking */
>> -               if (!locked) {
>> -                       locked = compact_lock_irqsave(&pgdat->lru_lock,
>> -                                                               &flags, cc);
>> +               if (lruvec != locked_lruvec) {
>> +                       if (locked_lruvec) {
>> +                               spin_unlock_irqrestore(&locked_lruvec->lru_lock,
>> +                                               locked_lruvec->irqflags);
>> +                               locked_lruvec = NULL;
>> +                       }
> What guarantees the lifetime of lruvec? You should read the comment on
> mem_cgroup_page_lruvec(). Have you seen the patches Hugh had shared?
> Please look at the  trylock_page_lruvec().
> 

Thanks for comments, Shakeel.

lruvec lifetime is same as memcg, which allocted in mem_cgroup_alloc()->alloc_mem_cgroup_per_node_info()
I have read Hugh's patchset, even not every lines. But what's point of you here?

> BTW have you tested Hugh's patches?
> 

yes, I have tried the case-lru-file-readtwice on my machine w/o containers, it show a bit more regression.

Thanks
Alex