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

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Message-ID: <5e55c6e64a2bfd6eed855ea17a34788b@codeaurora.org>
Date:   Wed, 07 Nov 2018 11:51:12 +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 2018-11-07 01:38, Michal Hocko wrote:
> On Tue 06-11-18 21:01:29, Arun KS wrote:
>> 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.
> 
> The ordering should be other way around. Because as things stand with
> this patch first it is possible to introduce a subtle race prone
> updates. As I've said I am skeptical the race would matter, really, but
> there is no real reason to risk for that. Especially when you have the
> other (first) half ready.

Makes sense. I have rebased the preparatory patch on top of -rc1.
https://patchwork.kernel.org/patch/10670787/

Regards,
Arun