linux-kernel - Re: [iov_iter] 9bd0e337c6: will-it-scale.per_process

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Message-ID: <8124ce0d-c934-0771-5e34-cf5ea030fc08@kernel.dk>
Date:   Thu, 3 Dec 2020 10:50:03 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        kernel test robot <oliver.sang@...el.com>
Cc:     David Howells <dhowells@...hat.com>, lkp@...ts.01.org,
        kernel test robot <lkp@...el.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        Feng Tang <feng.tang@...el.com>, zhengjun.xing@...el.com,
        Pavel Begunkov <asml.silence@...il.com>,
        Matthew Wilcox <willy@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [iov_iter] 9bd0e337c6: will-it-scale.per_process_ops -4.8%
 regression

On 12/3/20 10:47 AM, Linus Torvalds wrote:
> On Wed, Dec 2, 2020 at 10:31 PM kernel test robot <oliver.sang@...el.com> wrote:
>>
>> FYI, we noticed a -4.8% regression of will-it-scale.per_process_ops due to commit:
> 
> Ok, I guess that's bigger than expected, but the profile data does
> show how bad the indirect branches are.

It's also in the same range (3-6%) as the microbenchmarks I ran and posted.
So at least there's correlation there too.

-- 
Jens Axboe