linux-kernel - Re: [PATCH v1 0/4]mm: convert totalram_pages, totalhigh

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Message-ID: <33a9d26369468824e27de5a636e4e843@codeaurora.org>
Date:   Wed, 07 Nov 2018 11:49:44 +0530
From:   Arun KS <arunks@...eaurora.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     keescook@...omium.org, khlebnikov@...dex-team.ru,
        minchan@...nel.org, getarunks@...il.com,
        gregkh@...uxfoundation.org, mhocko@...nel.org, vbabka@...e.cz,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v1 0/4]mm: convert totalram_pages, totalhigh_pages and
 managed pages to atomic

On 2018-11-07 05:52, Andrew Morton wrote:
> On Fri, 26 Oct 2018 16:30:58 +0530 Arun KS <arunks@...eaurora.org> 
> wrote:
> 
>> This series convert totalram_pages, totalhigh_pages and
>> zone->managed_pages to atomic variables.
> 
> The whole point appears to be removal of managed_page_count_lock, yes?
> 
> Why?  What is the value of this patchset?  If "performance" then are 
> any
> measurements available?

Hello Andrew,

https://patchwork.kernel.org/patch/10670787/
In version 2, I have added motivation behind this conversion. Pasting 
same here,

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. I don't think we have a performance improvement here.

Regards,
Arun