From: Pavel Machek <pavel@denx.de>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Pavel Machek <pavel@denx.de>,
David Laight <David.Laight@ACULAB.COM>,
Christoph Hellwig <hch@lst.de>, "arnd@arndb.de" <arnd@arndb.de>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] /dev/zero: also implement ->read
Date: Sun, 6 Sep 2020 20:38:20 +0200 [thread overview]
Message-ID: <20200906183820.GA13290@amd> (raw)
In-Reply-To: <8c353864-76a9-90bf-fa2f-f7a8231b5487@csgroup.eu>
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On Sun 2020-09-06 20:35:38, Christophe Leroy wrote:
> Hi,
>
> Le 06/09/2020 à 20:21, Pavel Machek a écrit :
> >Hi!
> >
> >>>>Christophe reported a major speedup due to avoiding the iov_iter
> >>>>overhead, so just add this trivial function. Note that /dev/zero
> >>>>already implements both an iter and non-iter writes so this just
> >>>>makes it more symmetric.
> >>>>
> >>>>Christophe Leroy <christophe.leroy@csgroup.eu>
> >>>>Signed-off-by: Christoph Hellwig <hch@lst.de>
> >>>
> >>>Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> >>
> >>Any idea what has happened to make the 'iter' version so bad?
> >
> >Exactly. Also it would be nice to note how the speedup was measured
> >and what the speedup is.
> >
>
> Was measured on an 8xx powerpc running at 132MHz with:
>
> dd if=/dev/zero of=/dev/null count=1M
>
> With the patch, dd displays a throughput of 113.5MB/s
> Without the patch it is 99.9MB/s
Actually... that does not seem like a huge deal. read(/dev/zero) is
not that common operation.
Are you getting similar speedups on normal hardware?
Pavel
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DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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next prev parent reply other threads:[~2020-09-06 18:38 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-03 15:59 [PATCH] /dev/zero: also implement ->read Christoph Hellwig
2020-09-03 16:05 ` Christophe Leroy
2020-09-03 21:35 ` David Laight
2020-09-06 18:21 ` Pavel Machek
2020-09-06 18:35 ` Christophe Leroy
2020-09-06 18:38 ` Pavel Machek [this message]
2020-09-06 18:47 ` Christophe Leroy
2020-09-06 20:09 ` gregkh
2020-09-06 20:52 ` David Laight
2020-09-07 4:44 ` Christophe Leroy
2020-09-07 8:18 ` David Laight
2020-09-03 17:51 ` Christophe Leroy
2020-09-03 18:02 ` Greg KH
2020-09-06 22:34 ` Rasmus Villemoes
2020-09-07 6:20 ` Christoph Hellwig
2020-09-07 6:50 ` Rasmus Villemoes
2020-09-07 7:30 ` Christoph Hellwig
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