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

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Date:   Fri, 04 Jan 2019 10:35:58 +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 11:51, Arun KS wrote:
> 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/

Hello Michal,

Please review version 7 sent,
https://lore.kernel.org/patchwork/patch/1028908/

Regards,
Arun
> 
> Regards,
> Arun