linux-kernel - Re: [PATCH 0/2] optimise iov

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Message-ID: <72a1df1a-810b-5bf1-39bd-b702188a875b@kernel.dk>
Date:   Thu, 19 Nov 2020 10:20:02 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Begunkov <asml.silence@...il.com>,
        linux-block@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] optimise iov_iter

On 11/19/20 10:14 AM, Pavel Begunkov wrote:
> On 19/11/2020 16:46, Jens Axboe wrote:
>> On 11/19/20 8:29 AM, Pavel Begunkov wrote:
>>> The first patch optimises iov_iter_npages() for the bvec case, and the
>>> second helps code generation to kill unreachable code.
>>>
>>> Pavel Begunkov (2):
>>>   iov_iter: optimise iov_iter_npages for bvec
>>>   iov_iter: optimise iter type checking
>>>
>>>  include/linux/uio.h | 10 +++++-----
>>>  lib/iov_iter.c      | 10 +++++-----
>>>  2 files changed, 10 insertions(+), 10 deletions(-)
>>
>> Nice! Tested this and confirmed both the better code generation,
>> and reduction in overhead in iov_iter_npages().
> 
> Thanks! Did you find t-put/etc. boost with your setup?

Yeah, for this kind of test, if we shave 1% off the stack overhead,
that directly yields an increase in peak IOPS. My numbers were close
to yours, dropped about 1% of system overhead.

-- 
Jens Axboe