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

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Message-ID: <20190104085801.GH31793@dhcp22.suse.cz>
Date:   Fri, 4 Jan 2019 09:58:01 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Arun KS <arunks@...eaurora.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 Fri 04-01-19 10:35:58, Arun KS wrote:
> 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/

I believe I have give my Acked-by to this version already, and v7 indeed
has it. Are there any relevant changes since v6 for me to do the review
again. If yes you should have dropped the Acked-by.
-- 
Michal Hocko
SUSE Labs