linux-kernel - Re: [RFC PATCH 0/1] Large folios in block buffered IO path

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Message-ID: <fb026d85-7f2e-4ab5-a7e1-48bf071260cf@amd.com>
Date: Thu, 28 Nov 2024 16:53:54 +0530
From: Bharata B Rao <bharata@....com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Mateusz Guzik <mjguzik@...il.com>, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 linux-mm@...ck.org, nikunj@....com, vbabka@...e.cz, david@...hat.com,
 akpm@...ux-foundation.org, yuzhao@...gle.com, axboe@...nel.dk,
 viro@...iv.linux.org.uk, brauner@...nel.org, jack@...e.cz,
 joshdon@...gle.com, clm@...a.com
Subject: Re: [RFC PATCH 0/1] Large folios in block buffered IO path

On 28-Nov-24 10:07 AM, Bharata B Rao wrote:
> On 28-Nov-24 9:52 AM, Matthew Wilcox wrote:
>> On Thu, Nov 28, 2024 at 09:31:50AM +0530, Bharata B Rao wrote:
>>> However a point of concern is that FIO bandwidth comes down drastically
>>> after the change.
>>>
>>>         default                inode_lock-fix
>>> rw=30%
>>> Instance 1    r=55.7GiB/s,w=23.9GiB/s        r=9616MiB/s,w=4121MiB/s
>>> Instance 2    r=38.5GiB/s,w=16.5GiB/s        r=8482MiB/s,w=3635MiB/s
>>> Instance 3    r=37.5GiB/s,w=16.1GiB/s        r=8609MiB/s,w=3690MiB/s
>>> Instance 4    r=37.4GiB/s,w=16.0GiB/s        r=8486MiB/s,w=3637MiB/s
>>
>> Something this dramatic usually only happens when you enable a debugging
>> option.  Can you recheck that you're running both A and B with the same
>> debugging options both compiled in, and enabled?
> 
> It is the same kernel tree with and w/o Mateusz's inode_lock changes to 
> block/fops.c. I see the config remains same for both the builds.
> 
> Let me get a run for both base and patched case w/o running perf lock 
> contention to check if that makes a difference.

Without perf lock contention

                 default                         inode_lock-fix
rw=30%
Instance 1      r=54.6GiB/s,w=23.4GiB/s         r=11.4GiB/s,w=4992MiB/s
Instance 2      r=52.7GiB/s,w=22.6GiB/s         r=11.4GiB/s,w=4981MiB/s
Instance 3      r=53.3GiB/s,w=22.8GiB/s         r=12.7GiB/s,w=5575MiB/s
Instance 4      r=37.7GiB/s,w=16.2GiB/s         r=10.4GiB/s,w=4581MiB/s

> 
> Regards,
> Bharata.
>