linux-kernel - Re: [PATCH v5 2/4] mm: convert zone->managed

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Date:   Wed, 14 Nov 2018 19:21:54 +0000
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     Arun KS <arunks@...eaurora.org>
Cc:     keescook@...omium.org, khlebnikov@...dex-team.ru,
        minchan@...nel.org, getarunks@...il.com,
        gregkh@...uxfoundation.org, akpm@...ux-foundation.org,
        mhocko@...nel.org, vbabka@...e.cz, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, vatsa@...eaurora.org, willy@...radead.org
Subject: Re: [PATCH v5 2/4] mm: convert zone->managed_pages to atomic variable

On 18-11-13 12:03:08, Arun KS wrote:
> totalram_pages, zone->managed_pages and totalhigh_pages updates
> are protected by managed_page_count_lock, but readers never care
> about it. Convert these variables to atomic to avoid readers
> potentially seeing a store tear.
> 
> This patch converts zone->managed_pages. Subsequent patches will
> convert totalram_panges, totalhigh_pages and eventually
> managed_page_count_lock will be removed.
> 
> Main motivation was that managed_page_count_lock handling was
> complicating things. It was discussed in length here,
> https://lore.kernel.org/patchwork/patch/995739/#1181785
> So it seemes better to remove the lock and convert variables
> to atomic, with preventing poteintial store-to-read tearing as
> a bonus.
> 
> Suggested-by: Michal Hocko <mhocko@...e.com>
> Suggested-by: Vlastimil Babka <vbabka@...e.cz>
> Signed-off-by: Arun KS <arunks@...eaurora.org>
> Reviewed-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> Acked-by: Michal Hocko <mhocko@...e.com>
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Reviewed-by: Pavel Tatashin <pasha.tatashin@...een.com>