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Date: Mon, 11 Jan 2021 10:55:48 +0800 From: Ming Lei <ming.lei@...hat.com> To: Pavel Begunkov <asml.silence@...il.com> Cc: linux-block@...r.kernel.org, Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@...radead.org>, Matthew Wilcox <willy@...radead.org>, Johannes Weiner <hannes@...xchg.org>, Alexander Viro <viro@...iv.linux.org.uk>, "Darrick J . Wong" <darrick.wong@...cle.com>, "Martin K . Petersen" <martin.petersen@...cle.com>, Jonathan Corbet <corbet@....net>, linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org, io-uring@...r.kernel.org, linux-kernel@...r.kernel.org, target-devel@...r.kernel.org, linux-scsi@...r.kernel.org, linux-doc@...r.kernel.org, Christoph Hellwig <hch@....de> Subject: Re: [PATCH v3 5/7] iov_iter: optimise bvec iov_iter_advance() On Sat, Jan 09, 2021 at 04:03:01PM +0000, Pavel Begunkov wrote: > iov_iter_advance() is heavily used, but implemented through generic > means. For bvecs there is a specifically crafted function for that, so > use bvec_iter_advance() instead, it's faster and slimmer. > > Reviewed-by: Christoph Hellwig <hch@....de> > Signed-off-by: Pavel Begunkov <asml.silence@...il.com> > --- > lib/iov_iter.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/lib/iov_iter.c b/lib/iov_iter.c > index 7de304269641..9b1c109dc8a9 100644 > --- a/lib/iov_iter.c > +++ b/lib/iov_iter.c > @@ -1065,6 +1065,21 @@ static void pipe_advance(struct iov_iter *i, size_t size) > pipe_truncate(i); > } > > +static void iov_iter_bvec_advance(struct iov_iter *i, size_t size) > +{ > + struct bvec_iter bi; > + > + bi.bi_size = i->count; > + bi.bi_bvec_done = i->iov_offset; > + bi.bi_idx = 0; > + bvec_iter_advance(i->bvec, &bi, size); > + > + i->bvec += bi.bi_idx; > + i->nr_segs -= bi.bi_idx; > + i->count = bi.bi_size; > + i->iov_offset = bi.bi_bvec_done; > +} > + > void iov_iter_advance(struct iov_iter *i, size_t size) > { > if (unlikely(iov_iter_is_pipe(i))) { > @@ -1075,6 +1090,10 @@ void iov_iter_advance(struct iov_iter *i, size_t size) > i->count -= size; > return; > } > + if (iov_iter_is_bvec(i)) { > + iov_iter_bvec_advance(i, size); > + return; > + } > iterate_and_advance(i, size, v, 0, 0, 0) > } > EXPORT_SYMBOL(iov_iter_advance); > -- > 2.24.0 > Reviewed-by: Ming Lei <ming.lei@...hat.com> -- Ming
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