Messages in this thread | | | Subject | Re: [PATCH] /dev/zero: also implement ->read | From | Christophe Leroy <> | Date | Sun, 6 Sep 2020 20:35:38 +0200 |
| |
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
Christophe
| |