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.le...@csgroup.eu> > >>>>Signed-off-by: Christoph Hellwig <h...@lst.de> > >>> > >>>Tested-by: Christophe Leroy <christophe.le...@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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