From: Matthew Wilcox <willy@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Pavel Begunkov <asml.silence@gmail.com>,
Ming Lei <ming.lei@redhat.com>,
linux-fsdevel@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] iov_iter: optimise iov_iter_npages for bvec
Date: Fri, 20 Nov 2020 12:39:31 +0000 [thread overview]
Message-ID: <20201120123931.GN29991@casper.infradead.org> (raw)
In-Reply-To: <20201120081429.GA30801@infradead.org>
On Fri, Nov 20, 2020 at 08:14:29AM +0000, Christoph Hellwig wrote:
> On Fri, Nov 20, 2020 at 02:54:57AM +0000, Matthew Wilcox wrote:
> > On Fri, Nov 20, 2020 at 02:25:08AM +0000, Pavel Begunkov wrote:
> > > On 20/11/2020 02:22, Ming Lei wrote:
> > > > iov_iter_npages(bvec) still can be improved a bit by the following way:
> > >
> > > Yep, was doing exactly that, +a couple of other places that are in my way.
> >
> > Are you optimising the right thing here? Assuming you're looking at
> > the one in do_blockdev_direct_IO(), wouldn't we be better off figuring
> > out how to copy the bvecs directly from the iov_iter into the bio
> > rather than calling dio_bio_add_page() for each page?
>
> Which is most effectively done by stopping to to use *blockdev_direct_IO
> and switching to iomap instead :)
But iomap still calls iov_iter_npages(). So maybe we need something like
this ...
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 933f234d5bec..1c5a802a45d9 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -250,7 +250,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
orig_count = iov_iter_count(dio->submit.iter);
iov_iter_truncate(dio->submit.iter, length);
- nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES);
+ nr_pages = bio_iov_iter_npages(dio->submit.iter);
if (nr_pages <= 0) {
ret = nr_pages;
goto out;
@@ -308,7 +308,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
dio->size += n;
copied += n;
- nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES);
+ nr_pages = bio_iov_iter_npages(dio->submit.iter);
iomap_dio_submit_bio(dio, iomap, bio, pos);
pos += n;
} while (nr_pages);
diff --git a/include/linux/bio.h b/include/linux/bio.h
index c6d765382926..86cc74f84b30 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -10,6 +10,7 @@
#include <linux/ioprio.h>
/* struct bio, bio_vec and BIO_* flags are defined in blk_types.h */
#include <linux/blk_types.h>
+#include <linux/uio.h>
#define BIO_DEBUG
@@ -447,6 +448,16 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
void __bio_add_page(struct bio *bio, struct page *page,
unsigned int len, unsigned int off);
int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter);
+
+static inline int bio_iov_iter_npages(const struct iov_iter *i)
+{
+ if (!iov_iter_count(i))
+ return 0;
+ if (iov_iter_is_bvec(i))
+ return 1;
+ return iov_iter_npages(i, BIO_MAX_PAGES);
+}
+
void bio_release_pages(struct bio *bio, bool mark_dirty);
extern void bio_set_pages_dirty(struct bio *bio);
extern void bio_check_pages_dirty(struct bio *bio);
next prev parent reply other threads:[~2020-11-20 12:39 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-19 23:24 [PATCH v2 0/2] optimise iov_iter Pavel Begunkov
2020-11-19 23:24 ` [PATCH v2 1/2] iov_iter: optimise iov_iter_npages for bvec Pavel Begunkov
2020-11-20 1:20 ` Matthew Wilcox
2020-11-20 1:39 ` Pavel Begunkov
2020-11-20 1:49 ` Matthew Wilcox
2020-11-20 1:56 ` Pavel Begunkov
2020-11-20 2:06 ` Matthew Wilcox
2020-11-20 2:08 ` Pavel Begunkov
2020-11-20 2:24 ` Ming Lei
2020-11-20 17:22 ` Pavel Begunkov
2020-11-20 17:23 ` Pavel Begunkov
2020-11-20 2:22 ` Ming Lei
2020-11-20 2:25 ` Pavel Begunkov
2020-11-20 2:54 ` Matthew Wilcox
2020-11-20 8:14 ` Christoph Hellwig
2020-11-20 12:39 ` Matthew Wilcox [this message]
2020-11-20 13:00 ` Pavel Begunkov
2020-11-20 13:13 ` Matthew Wilcox
2020-11-20 9:57 ` Pavel Begunkov
2020-11-20 13:29 ` David Laight
2020-11-19 23:24 ` [PATCH v2 2/2] iov_iter: optimise iter type checking Pavel Begunkov
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