linux-kernel - Re: [PATCH v6 1/2] memory_hotplug: Free pages as higher order

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <542cd3516b54d88d1bffede02c6045b8@codeaurora.org>
Date:   Tue, 06 Nov 2018 21:01:29 +0530
From:   Arun KS <arunks@...eaurora.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     arunks.linux@...il.com, akpm@...ux-foundation.org, vbabka@...e.cz,
        osalvador@...e.de, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, getarunks@...il.com
Subject: Re: [PATCH v6 1/2] memory_hotplug: Free pages as higher order

On 2018-11-06 19:36, Michal Hocko wrote:
> On Tue 06-11-18 11:33:13, Arun KS wrote:
>> When free pages are done with higher order, time spend on
>> coalescing pages by buddy allocator can be reduced. With
>> section size of 256MB, hot add latency of a single section
>> shows improvement from 50-60 ms to less than 1 ms, hence
>> improving the hot add latency by 60%. Modify external
>> providers of online callback to align with the change.
>> 
>> This patch modifies totalram_pages, zone->managed_pages and
>> totalhigh_pages outside managed_page_count_lock. A follow up
>> series will be send to convert these variable to atomic to
>> avoid readers potentially seeing a store tear.
> 
> Is there any reason to rush this through rather than wait for counters
> conversion first?

Sure Michal.

Conversion patch, https://patchwork.kernel.org/cover/10657217/ is 
currently incremental to this patch. I ll change the order. Will wait 
for preparatory patch to settle first.

Regards,
Arun.

> 
> The patch as is looks good to me - modulo atomic counters of course. I
> cannot really judge whether existing updaters do really race in 
> practice
> to take this riskless.
> 
> The improvement is nice of course but this is a rare operation and 50ms
> vs 1ms is hardly noticeable. So I would rather wait for the preparatory
> work to settle. Btw. is there anything blocking that? It seems to be
> mostly automated.