Messages in this thread | | | Date | Thu, 24 Jul 2014 09:15:55 +0800 | From | Gu Zheng <> | Subject | Re: [RESEND PATCH 4/4] aio: use iovec array rather than the single one |
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Hi Jeff, On 07/23/2014 09:25 PM, Jeff Moyer wrote:
> Gu Zheng <guz.fnst@cn.fujitsu.com> writes: > >> Previously, we only offer a single iovec to handle all the read/write cases, so >> the PREADV/PWRITEV request always need to alloc more iovec buffer when copying >> user vectors. >> If we use a tmp iovec array rather than the single one, some small PREADV/PWRITEV >> workloads(vector size small than the tmp buffer) will not need to alloc more >> iovec buffer when copying user vectors. > > Hi, Gu, > > This still doesn't explain why you decided to look into this.
The comment is clear, just want to avoid some needless memory allocation in the io submit path.
> Did you > notice a performance issue in this path? Do you have benchmarks that > show some speedup due to this change?
Just some common tests based on fio, it gains a slight improvement(~3%) when the iodepth in [5,6,7] than before. I did not paste these info here, because I think other guys(especially the guys have production environment) who are interested in this can give us more meaningful feedback.
Thanks, Gu
> > Thanks, > Jeff > >> >> Reviewed-by: Jeff Moyer <jmoyer@redhat.com> >> Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com> >> --- >> fs/aio.c | 10 +++++----- >> 1 files changed, 5 insertions(+), 5 deletions(-) >> >> diff --git a/fs/aio.c b/fs/aio.c >> index f1fede2..df3491a 100644 >> --- a/fs/aio.c >> +++ b/fs/aio.c >> @@ -1267,12 +1267,12 @@ static ssize_t aio_setup_vectored_rw(struct kiocb *kiocb, >> if (compat) >> ret = compat_rw_copy_check_uvector(rw, >> (struct compat_iovec __user *)buf, >> - *nr_segs, 1, *iovec, iovec); >> + *nr_segs, UIO_FASTIOV, *iovec, iovec); >> else >> #endif >> ret = rw_copy_check_uvector(rw, >> (struct iovec __user *)buf, >> - *nr_segs, 1, *iovec, iovec); >> + *nr_segs, UIO_FASTIOV, *iovec, iovec); >> if (ret < 0) >> return ret; >> >> @@ -1309,7 +1309,7 @@ static ssize_t aio_run_iocb(struct kiocb *req, unsigned opcode, >> fmode_t mode; >> aio_rw_op *rw_op; >> rw_iter_op *iter_op; >> - struct iovec inline_vec, *iovec = &inline_vec; >> + struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs; >> struct iov_iter iter; >> >> switch (opcode) { >> @@ -1344,7 +1344,7 @@ rw_common: >> if (!ret) >> ret = rw_verify_area(rw, file, &req->ki_pos, req->ki_nbytes); >> if (ret < 0) { >> - if (iovec != &inline_vec) >> + if (iovec != inline_vecs) >> kfree(iovec); >> return ret; >> } >> @@ -1391,7 +1391,7 @@ rw_common: >> return -EINVAL; >> } >> >> - if (iovec != &inline_vec) >> + if (iovec != inline_vecs) >> kfree(iovec); >> >> if (ret != -EIOCBQUEUED) { > . >
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