linux-kernel - Re: [RFC for-next v2 0/4] enable pcpu bio caching for IRQ I/O

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Date:   Thu, 20 Oct 2022 05:53:07 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Begunkov <asml.silence@...il.com>,
        Christoph Hellwig <hch@...radead.org>
Cc:     linux-block@...r.kernel.org, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [RFC for-next v2 0/4] enable pcpu bio caching for IRQ I/O

On 10/20/22 5:40 AM, Pavel Begunkov wrote:
> On 10/20/22 09:32, Christoph Hellwig wrote:
>> On Tue, Oct 18, 2022 at 08:50:54PM +0100, Pavel Begunkov wrote:
>>> This series implements bio pcpu caching for normal / IRQ-driven I/O
>>> extending REQ_ALLOC_CACHE currently limited to iopoll. The allocation side
>>> still only works from non-irq context, which is the reason it's not enabled
>>> by default, but turning it on for other users (e.g. filesystems) is
>>> as a matter of passing a flag.
>>>
>>> t/io_uring with an Optane SSD setup showed +7% for batches of 32 requests
>>> and +4.3% for batches of 8.
>>
>> This looks much nicer to me than the previous attempt exposing the bio
>> internals to io_uring, thanks.
> 
> Yeah, I saw the one Jens posted before but I wanted this one to be more
> generic, i.e. applicable not only to io_uring. Thanks for taking a look.

It is indeed better like that, also because we can get rid of the alloc
cache flag long term and just have it be the way that bio allocations
work.

-- 
Jens Axboe