linux-kernel - Re: [PATCH] target/file: don't zero iter before iov_iter

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Date:   Sat, 9 Jan 2021 21:25:53 +0000
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>
Cc:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "target-devel@...r.kernel.org" <target-devel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] target/file: don't zero iter before iov_iter_bvec

On 09/01/2021 20:52, Chaitanya Kulkarni wrote:
> On 1/9/21 12:40, Pavel Begunkov wrote:
>> I expect you won't find any, but such little things can pile up
>> into a not-easy-to-spot overhead over time.
> 
> That is what I suspected with the resulting assembly. The commit log
> needs to document that there is no direct impact on the performance

It's obvious that 3-4 extra mov $0 off(%reg) won't change performance
but still hasn't been formally confirmed ...

> which can be seen with this patch, but this is nice to have

... so if you don't mind, I won't be resending just for that.

-- 
Pavel Begunkov