linux-kernel - Re: [mm PATCH v3 1/6] mm: Use mm_zero_struct_page from SPARC on all 64b architectures

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 17 Oct 2018 07:52:16 -0700
From:   Alexander Duyck <alexander.h.duyck@...ux.intel.com>
To:     Mike Rapoport <rppt@...ux.ibm.com>,
        Pavel Tatashin <pasha.tatashin@...il.com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        pavel.tatashin@...rosoft.com, mhocko@...e.com,
        dave.jiang@...el.com, linux-kernel@...r.kernel.org,
        willy@...radead.org, davem@...emloft.net,
        yi.z.zhang@...ux.intel.com, khalid.aziz@...cle.com,
        rppt@...ux.vnet.ibm.com, vbabka@...e.cz,
        sparclinux@...r.kernel.org, dan.j.williams@...el.com,
        ldufour@...ux.vnet.ibm.com, mgorman@...hsingularity.net,
        mingo@...nel.org, kirill.shutemov@...ux.intel.com
Subject: Re: [mm PATCH v3 1/6] mm: Use mm_zero_struct_page from SPARC on all
 64b architectures

On 10/17/2018 12:30 AM, Mike Rapoport wrote:
> On Tue, Oct 16, 2018 at 03:01:11PM -0400, Pavel Tatashin wrote:
>>
>>
>> On 10/15/18 4:26 PM, Alexander Duyck wrote:
>>> This change makes it so that we use the same approach that was already in
>>> use on Sparc on all the archtectures that support a 64b long.
>>>
>>> This is mostly motivated by the fact that 8 to 10 store/move instructions
>>> are likely always going to be faster than having to call into a function
>>> that is not specialized for handling page init.
>>>
>>> An added advantage to doing it this way is that the compiler can get away
>>> with combining writes in the __init_single_page call. As a result the
>>> memset call will be reduced to only about 4 write operations, or at least
>>> that is what I am seeing with GCC 6.2 as the flags, LRU poitners, and
>>> count/mapcount seem to be cancelling out at least 4 of the 8 assignments on
>>> my system.
>>>
>>> One change I had to make to the function was to reduce the minimum page
>>> size to 56 to support some powerpc64 configurations.
>>>
>>> Signed-off-by: Alexander Duyck <alexander.h.duyck@...ux.intel.com>
>>
>>
>> I have tested on Broadcom's Stingray cpu with 48G RAM:
>> __init_single_page() takes 19.30ns / 64-byte struct page
>> Wit the change it takes 17.33ns / 64-byte struct page
>   
> I gave it a run on an OpenPower (S812LC 8348-21C) with Power8 processor and
> with 128G of RAM. My results for 64-byte struct page were:
> 
> before: 4.6788ns
> after: 4.5882ns
> 
> My two cents :)

Thanks. I will add this and Pavel's data to the patch description.

- Alex