* [PATCH 0/2] optimise bvec/bio iteration
@ 2020-11-24 17:58 Pavel Begunkov
2020-11-24 17:58 ` [PATCH 1/2] block: optimise for_each_bvec() advance Pavel Begunkov
` (2 more replies)
0 siblings, 3 replies; 9+ messages in thread
From: Pavel Begunkov @ 2020-11-24 17:58 UTC (permalink / raw)
To: Jens Axboe, linux-block; +Cc: Ming Lei, Christoph Hellwig
This adds simpler versions of bvec_iter_advance() and bio_advance_iter()
(i.e. *_single()), that are faster but work with the restriction that
@bytes shouldn't be more than available in the current bvec segment.
That covers most of bvec/bio iteration/foreach, that are massively
inlined, and thus also nicely shrinks binary.
Others non core-block users might be updated on case by case basis
(if applicable) after the change is merged.
Pavel Begunkov (2):
block: optimise for_each_bvec() advance
bio: optimise bvec iteration
block/bio.c | 4 ++--
include/linux/bio.h | 17 +++++++++++++++--
include/linux/bvec.h | 20 +++++++++++++++-----
3 files changed, 32 insertions(+), 9 deletions(-)
--
2.24.0
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 1/2] block: optimise for_each_bvec() advance
2020-11-24 17:58 [PATCH 0/2] optimise bvec/bio iteration Pavel Begunkov
@ 2020-11-24 17:58 ` Pavel Begunkov
2020-11-26 10:00 ` Christoph Hellwig
2020-11-24 17:58 ` [PATCH 2/2] bio: optimise bvec iteration Pavel Begunkov
2020-12-02 16:47 ` [PATCH 0/2] optimise bvec/bio iteration Jens Axboe
2 siblings, 1 reply; 9+ messages in thread
From: Pavel Begunkov @ 2020-11-24 17:58 UTC (permalink / raw)
To: Jens Axboe, linux-block; +Cc: Ming Lei, Christoph Hellwig
Because of how for_each_bvec() works it never advances across multiple
entries at a time, so bvec_iter_advance() is an overkill. Add
specialised bvec_iter_advance_single() that is faster. It also handles
zero-len bvecs, so can kill bvec_iter_skip_zero_bvec().
text data bss dec hex filename
before:
23977 805 0 24782 60ce lib/iov_iter.o
before, bvec_iter_advance() w/o WARN_ONCE()
22886 600 0 23486 5bbe ./lib/iov_iter.o
after:
21862 600 0 22462 57be lib/iov_iter.o
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
include/linux/bvec.h | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 2efec10bf792..ff832e698efb 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -121,18 +121,28 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
return true;
}
-static inline void bvec_iter_skip_zero_bvec(struct bvec_iter *iter)
+/*
+ * A simpler version of bvec_iter_advance(), @bytes should not span
+ * across multiple bvec entries, i.e. bytes <= bv[i->bi_idx].bv_len
+ */
+static inline void bvec_iter_advance_single(const struct bio_vec *bv,
+ struct bvec_iter *iter, unsigned int bytes)
{
- iter->bi_bvec_done = 0;
- iter->bi_idx++;
+ unsigned int done = iter->bi_bvec_done + bytes;
+
+ if (done == bv[iter->bi_idx].bv_len) {
+ done = 0;
+ iter->bi_idx++;
+ }
+ iter->bi_bvec_done = done;
+ iter->bi_size -= bytes;
}
#define for_each_bvec(bvl, bio_vec, iter, start) \
for (iter = (start); \
(iter).bi_size && \
((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
- (bvl).bv_len ? (void)bvec_iter_advance((bio_vec), &(iter), \
- (bvl).bv_len) : bvec_iter_skip_zero_bvec(&(iter)))
+ bvec_iter_advance_single((bio_vec), &(iter), (bvl).bv_len))
/* for iterating one bio from start to end */
#define BVEC_ITER_ALL_INIT (struct bvec_iter) \
--
2.24.0
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 2/2] bio: optimise bvec iteration
2020-11-24 17:58 [PATCH 0/2] optimise bvec/bio iteration Pavel Begunkov
2020-11-24 17:58 ` [PATCH 1/2] block: optimise for_each_bvec() advance Pavel Begunkov
@ 2020-11-24 17:58 ` Pavel Begunkov
2020-11-26 10:02 ` Christoph Hellwig
2020-12-02 14:56 ` Christoph Hellwig
2020-12-02 16:47 ` [PATCH 0/2] optimise bvec/bio iteration Jens Axboe
2 siblings, 2 replies; 9+ messages in thread
From: Pavel Begunkov @ 2020-11-24 17:58 UTC (permalink / raw)
To: Jens Axboe, linux-block; +Cc: Ming Lei, Christoph Hellwig
__bio_for_each_bvec(), __bio_for_each_segment() and bio_copy_data_iter()
fall under conditions of bvec_iter_advance_single(), which is a faster
and slimmer version of bvec_iter_advance(). Add
bio_advance_iter_single() and convert them.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
block/bio.c | 4 ++--
include/linux/bio.h | 17 +++++++++++++++--
2 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index fa01bef35bb1..8e718920457a 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1212,8 +1212,8 @@ void bio_copy_data_iter(struct bio *dst, struct bvec_iter *dst_iter,
flush_dcache_page(dst_bv.bv_page);
- bio_advance_iter(src, src_iter, bytes);
- bio_advance_iter(dst, dst_iter, bytes);
+ bio_advance_iter_single(src, src_iter, bytes);
+ bio_advance_iter_single(dst, dst_iter, bytes);
}
}
EXPORT_SYMBOL(bio_copy_data_iter);
diff --git a/include/linux/bio.h b/include/linux/bio.h
index c6d765382926..d55d53c49ae4 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -148,11 +148,24 @@ static inline void bio_advance_iter(const struct bio *bio,
/* TODO: It is reasonable to complete bio with error here. */
}
+/* @bytes should be less or equal to bvec[i->bi_idx].bv_len */
+static inline void bio_advance_iter_single(const struct bio *bio,
+ struct bvec_iter *iter,
+ unsigned int bytes)
+{
+ iter->bi_sector += bytes >> 9;
+
+ if (bio_no_advance_iter(bio))
+ iter->bi_size -= bytes;
+ else
+ bvec_iter_advance_single(bio->bi_io_vec, iter, bytes);
+}
+
#define __bio_for_each_segment(bvl, bio, iter, start) \
for (iter = (start); \
(iter).bi_size && \
((bvl = bio_iter_iovec((bio), (iter))), 1); \
- bio_advance_iter((bio), &(iter), (bvl).bv_len))
+ bio_advance_iter_single((bio), &(iter), (bvl).bv_len))
#define bio_for_each_segment(bvl, bio, iter) \
__bio_for_each_segment(bvl, bio, iter, (bio)->bi_iter)
@@ -161,7 +174,7 @@ static inline void bio_advance_iter(const struct bio *bio,
for (iter = (start); \
(iter).bi_size && \
((bvl = mp_bvec_iter_bvec((bio)->bi_io_vec, (iter))), 1); \
- bio_advance_iter((bio), &(iter), (bvl).bv_len))
+ bio_advance_iter_single((bio), &(iter), (bvl).bv_len))
/* iterate over multi-page bvec */
#define bio_for_each_bvec(bvl, bio, iter) \
--
2.24.0
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH 1/2] block: optimise for_each_bvec() advance
2020-11-24 17:58 ` [PATCH 1/2] block: optimise for_each_bvec() advance Pavel Begunkov
@ 2020-11-26 10:00 ` Christoph Hellwig
0 siblings, 0 replies; 9+ messages in thread
From: Christoph Hellwig @ 2020-11-26 10:00 UTC (permalink / raw)
To: Pavel Begunkov; +Cc: Jens Axboe, linux-block, Ming Lei, Christoph Hellwig
On Tue, Nov 24, 2020 at 05:58:12PM +0000, Pavel Begunkov wrote:
> Because of how for_each_bvec() works it never advances across multiple
> entries at a time, so bvec_iter_advance() is an overkill. Add
> specialised bvec_iter_advance_single() that is faster. It also handles
> zero-len bvecs, so can kill bvec_iter_skip_zero_bvec().
>
> text data bss dec hex filename
> before:
> 23977 805 0 24782 60ce lib/iov_iter.o
> before, bvec_iter_advance() w/o WARN_ONCE()
> 22886 600 0 23486 5bbe ./lib/iov_iter.o
> after:
> 21862 600 0 22462 57be lib/iov_iter.o
>
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 2/2] bio: optimise bvec iteration
2020-11-24 17:58 ` [PATCH 2/2] bio: optimise bvec iteration Pavel Begunkov
@ 2020-11-26 10:02 ` Christoph Hellwig
2020-11-26 12:32 ` Pavel Begunkov
2020-12-02 14:56 ` Christoph Hellwig
1 sibling, 1 reply; 9+ messages in thread
From: Christoph Hellwig @ 2020-11-26 10:02 UTC (permalink / raw)
To: Pavel Begunkov; +Cc: Jens Axboe, linux-block, Ming Lei, Christoph Hellwig
On Tue, Nov 24, 2020 at 05:58:13PM +0000, Pavel Begunkov wrote:
> __bio_for_each_bvec(), __bio_for_each_segment() and bio_copy_data_iter()
> fall under conditions of bvec_iter_advance_single(), which is a faster
> and slimmer version of bvec_iter_advance(). Add
> bio_advance_iter_single() and convert them.
Are you sure about bio_advance_iter()? That API looks like it might
not always be limited to a single segment, and might at least need a
WARN_ON_ONCE to make sure it is not abused.
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 2/2] bio: optimise bvec iteration
2020-11-26 10:02 ` Christoph Hellwig
@ 2020-11-26 12:32 ` Pavel Begunkov
2020-12-02 13:50 ` Pavel Begunkov
0 siblings, 1 reply; 9+ messages in thread
From: Pavel Begunkov @ 2020-11-26 12:32 UTC (permalink / raw)
To: Christoph Hellwig; +Cc: Jens Axboe, linux-block, Ming Lei
On 26/11/2020 10:02, Christoph Hellwig wrote:
> On Tue, Nov 24, 2020 at 05:58:13PM +0000, Pavel Begunkov wrote:
>> __bio_for_each_bvec(), __bio_for_each_segment() and bio_copy_data_iter()
>> fall under conditions of bvec_iter_advance_single(), which is a faster
>> and slimmer version of bvec_iter_advance(). Add
>> bio_advance_iter_single() and convert them.
>
> Are you sure about bio_advance_iter()? That API looks like it might
Both those listed bio_for_each*() pass bvl.bv_len, which is truncated to
current segment by bio_iter_iovec() (i.e. bvec_iter_bvec) or
mp_bvec_iter_bvec().
And just to note that I didn't change bio_advance_iter() but added a
new function.
There is always space for stupid mistakes, but I'm sure. What makes you
to think opposite? I may have missed it.
> not always be limited to a single segment, and might at least need a
> WARN_ON_ONCE to make sure it is not abused.
I thought twice about converting other places as you commented before,
and it looks saner to not do that exactly for that reason. I prefer
to leave *_single() versions for rare but high impact cases like
for_each()s.
And as it's contained I decided to not add overhead on WARN_ONCE(),
e.g. with inlining and w/o string dedup it grows .data section much.
--
Pavel Begunkov
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 2/2] bio: optimise bvec iteration
2020-11-26 12:32 ` Pavel Begunkov
@ 2020-12-02 13:50 ` Pavel Begunkov
0 siblings, 0 replies; 9+ messages in thread
From: Pavel Begunkov @ 2020-12-02 13:50 UTC (permalink / raw)
To: Christoph Hellwig; +Cc: Jens Axboe, linux-block, Ming Lei
On 26/11/2020 12:32, Pavel Begunkov wrote:
> On 26/11/2020 10:02, Christoph Hellwig wrote:
>> On Tue, Nov 24, 2020 at 05:58:13PM +0000, Pavel Begunkov wrote:
>>> __bio_for_each_bvec(), __bio_for_each_segment() and bio_copy_data_iter()
>>> fall under conditions of bvec_iter_advance_single(), which is a faster
>>> and slimmer version of bvec_iter_advance(). Add
>>> bio_advance_iter_single() and convert them.
>>
>> Are you sure about bio_advance_iter()? That API looks like it might
>
> Both those listed bio_for_each*() pass bvl.bv_len, which is truncated to
> current segment by bio_iter_iovec() (i.e. bvec_iter_bvec) or
> mp_bvec_iter_bvec().
>
> And just to note that I didn't change bio_advance_iter() but added a
> new function.
> There is always space for stupid mistakes, but I'm sure. What makes you
> to think opposite? I may have missed it.
Christoph, any doubts left?
>> not always be limited to a single segment, and might at least need a
>> WARN_ON_ONCE to make sure it is not abused.
>
> I thought twice about converting other places as you commented before,
> and it looks saner to not do that exactly for that reason. I prefer
> to leave *_single() versions for rare but high impact cases like
> for_each()s.
> And as it's contained I decided to not add overhead on WARN_ONCE(),
> e.g. with inlining and w/o string dedup it grows .data section much.
>
--
Pavel Begunkov
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 2/2] bio: optimise bvec iteration
2020-11-24 17:58 ` [PATCH 2/2] bio: optimise bvec iteration Pavel Begunkov
2020-11-26 10:02 ` Christoph Hellwig
@ 2020-12-02 14:56 ` Christoph Hellwig
1 sibling, 0 replies; 9+ messages in thread
From: Christoph Hellwig @ 2020-12-02 14:56 UTC (permalink / raw)
To: Pavel Begunkov; +Cc: Jens Axboe, linux-block, Ming Lei, Christoph Hellwig
On Tue, Nov 24, 2020 at 05:58:13PM +0000, Pavel Begunkov wrote:
> __bio_for_each_bvec(), __bio_for_each_segment() and bio_copy_data_iter()
> fall under conditions of bvec_iter_advance_single(), which is a faster
> and slimmer version of bvec_iter_advance(). Add
> bio_advance_iter_single() and convert them.
>
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 0/2] optimise bvec/bio iteration
2020-11-24 17:58 [PATCH 0/2] optimise bvec/bio iteration Pavel Begunkov
2020-11-24 17:58 ` [PATCH 1/2] block: optimise for_each_bvec() advance Pavel Begunkov
2020-11-24 17:58 ` [PATCH 2/2] bio: optimise bvec iteration Pavel Begunkov
@ 2020-12-02 16:47 ` Jens Axboe
2 siblings, 0 replies; 9+ messages in thread
From: Jens Axboe @ 2020-12-02 16:47 UTC (permalink / raw)
To: Pavel Begunkov, linux-block; +Cc: Ming Lei, Christoph Hellwig
On 11/24/20 10:58 AM, Pavel Begunkov wrote:
> This adds simpler versions of bvec_iter_advance() and bio_advance_iter()
> (i.e. *_single()), that are faster but work with the restriction that
> @bytes shouldn't be more than available in the current bvec segment.
>
> That covers most of bvec/bio iteration/foreach, that are massively
> inlined, and thus also nicely shrinks binary.
>
> Others non core-block users might be updated on case by case basis
> (if applicable) after the change is merged.
Applied, thanks.
--
Jens Axboe
^ permalink raw reply [flat|nested] 9+ messages in thread
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2020-11-24 17:58 [PATCH 0/2] optimise bvec/bio iteration Pavel Begunkov
2020-11-24 17:58 ` [PATCH 1/2] block: optimise for_each_bvec() advance Pavel Begunkov
2020-11-26 10:00 ` Christoph Hellwig
2020-11-24 17:58 ` [PATCH 2/2] bio: optimise bvec iteration Pavel Begunkov
2020-11-26 10:02 ` Christoph Hellwig
2020-11-26 12:32 ` Pavel Begunkov
2020-12-02 13:50 ` Pavel Begunkov
2020-12-02 14:56 ` Christoph Hellwig
2020-12-02 16:47 ` [PATCH 0/2] optimise bvec/bio iteration Jens Axboe
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