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

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Date:   Tue, 3 Oct 2017 16:26:51 -0400
From:   Pasha Tatashin <pasha.tatashin@...cle.com>
To:     Michal Hocko <mhocko@...nel.org>
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

Hi Michal,

I decided not to merge these two patches, because in addition to sparc 
optimization move, we have this dependancies:

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.

However, the first patch depends on
mm: zero struct pages during initialization

As it uses mm_zero_struct_page().

Pasha


On 10/03/2017 11:34 AM, Pasha Tatashin wrote:
> On 10/03/2017 09:19 AM, Michal Hocko wrote:
>> On Wed 20-09-17 16:17:14, Pavel Tatashin wrote:
>>> vmemmap_alloc_block() will no longer zero the block, so zero memory
>>> at its call sites for everything except struct pages.  Struct page 
>>> memory
>>> is zero'd by struct page initialization.
>>>
>>> Replace allocators in sprase-vmemmap to use the non-zeroing version. So,
>>> we will get the performance improvement by zeroing the memory in 
>>> parallel
>>> when struct pages are zeroed.
>>
>> Is it possible to merge this patch with 
>> http://lkml.kernel.org/r/20170920201714.19817-7-pasha.tatashin@oracle.com
> 
> Yes, I will do that. It would also require re-arranging
> [PATCH v9 07/12] sparc64: optimized struct page zeroing
> optimization to come after this patch.
> 
> Pasha