linux-kernel - Re: [PATCH v9 12/12] mm: stop zeroing memory during allocation in vmemmap

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Message-ID: <20171004084526.57uzy3t4ualwxdyt@dhcp22.suse.cz>
Date:   Wed, 4 Oct 2017 10:45:26 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Pasha Tatashin <pasha.tatashin@...cle.com>
Cc:     linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        x86@...nel.org, kasan-dev@...glegroups.com, borntraeger@...ibm.com,
        heiko.carstens@...ibm.com, davem@...emloft.net,
        willy@...radead.org, ard.biesheuvel@...aro.org,
        mark.rutland@....com, will.deacon@....com, catalin.marinas@....com,
        sam@...nborg.org, mgorman@...hsingularity.net,
        steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        bob.picco@...cle.com
Subject: Re: [PATCH v9 12/12] mm: stop zeroing memory during allocation in
 vmemmap

On Tue 03-10-17 16:26:51, Pasha Tatashin wrote:
> Hi Michal,
> 
> I decided not to merge these two patches, because in addition to sparc
> optimization move, we have this dependancies:

optimizations can and should go on top of the core patch.

> mm: zero reserved and unavailable struct pages
> 
> must be before
> 
> mm: stop zeroing memory during allocation in vmemmap.
> 
> Otherwise, we can end-up with struct pages that are not zeroed properly.

Right and you can deal with it easily. Just introduce the
mm_zero_struct_page earlier along with its user in "stop zeroing ..."

I think that moving the zeroying in one go is more reasonable than
adding it to __init_single_page with misleading numbers and later
dropping the zeroying from the memmap path.
-- 
Michal Hocko
SUSE Labs