linux-kernel - Re: [PATCH v3 2/7] mm/lruvec: add irqsave flags into lruvec struct

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Date:   Fri, 15 Nov 2019 22:31:22 -0800
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Alex Shi <alex.shi@...ux.alibaba.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>,
        Vlastimil Babka <vbabka@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Michal Hocko <mhocko@...e.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Arun KS <arunks@...eaurora.org>,
        Rong Chen <rong.a.chen@...el.com>
Subject: Re: [PATCH v3 2/7] mm/lruvec: add irqsave flags into lruvec struct

On Fri, Nov 15, 2019 at 7:15 PM Alex Shi <alex.shi@...ux.alibaba.com> wrote:
>
> We need a irqflags vaiable to save state when do irqsave action, declare
> it here would make code more clear/clean.
>
> Rong Chen <rong.a.chen@...el.com> reported the 'irqflags' variable need
> move to the tail of lruvec struct otherwise it causes 18% regressions of
> vm-scalability testing on his machine. So add the flags and lru_lock to
> both near struct tail, even I have no clue of this perf losing.

Regressions compared to what? Also no need to have a separate patch.

>
> Originally-from: Hugh Dickins <hughd@...gle.com>
> Signed-off-by: Alex Shi <alex.shi@...ux.alibaba.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Wei Yang <richard.weiyang@...il.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Arun KS <arunks@...eaurora.org>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> CC: Rong Chen <rong.a.chen@...el.com>
> Cc: cgroups@...r.kernel.org
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  include/linux/mmzone.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index a13b8a602ee5..9b8b8daf4e03 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -269,6 +269,8 @@ struct lruvec {
>         unsigned long                   flags;
>         /* per lruvec lru_lock for memcg */
>         spinlock_t                      lru_lock;
> +       /* flags for irqsave */
> +       unsigned long                   irqflags;
>  #ifdef CONFIG_MEMCG
>         struct pglist_data *pgdat;
>  #endif
> --
> 1.8.3.1
>