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* [PATCH 0/2] block: add bio split counters for iostat
@ 2019-12-09 13:57 Aleksei Zakharov
  2019-12-09 13:58 ` [PATCH 1/2] block: extend bi_flags to int and introduce BIO_SPLITTED Aleksei Zakharov
  2019-12-09 13:58 ` [PATCH 2/2] block: add iostat counters for requests splits Aleksei Zakharov
  0 siblings, 2 replies; 5+ messages in thread
From: Aleksei Zakharov @ 2019-12-09 13:57 UTC (permalink / raw)
  To: linux-block; +Cc: Aleksei Zakharov

There's a mechanism which splits IO's if their size
is greater than queue/max_sectors_kb setting. But there's
no counter for split requests. Having splits counter helps
to understand workload profile and necessity
of settings tuning.


bi_flags converted to int from short.
Add BIO_SPLITTED flag and set it in bio_split() for new bio.
Add splits[] counters.
In blk_account_io_start() check the BIO_SPLITTED flag
and if it's set increment appropriate splits counter.

Aleksei Zakharov (2):
  block: extend bi_flags to int and introduce BIO_SPLITTED
  block: add iostat counters for requests splits

 Documentation/ABI/testing/procfs-diskstats |  3 +++
 Documentation/ABI/testing/sysfs-block      |  5 ++++-
 Documentation/admin-guide/iostats.rst      | 10 ++++++++++
 block/bio.c                                |  2 ++
 block/blk-core.c                           |  2 ++
 block/genhd.c                              |  8 ++++++--
 block/partition-generic.c                  |  8 ++++++--
 include/linux/blk_types.h                  |  5 +++--
 include/linux/genhd.h                      |  1 +
 9 files changed, 37 insertions(+), 7 deletions(-)

-- 
2.17.1


^ permalink raw reply	[flat|nested] 5+ messages in thread
* [PATCH 1/2] block: extend bi_flags to int and introduce BIO_SPLITTED
  2019-12-09 13:57 [PATCH 0/2] block: add bio split counters for iostat Aleksei Zakharov
@ 2019-12-09 13:58 ` Aleksei Zakharov
  2019-12-09 13:58 ` [PATCH 2/2] block: add iostat counters for requests splits Aleksei Zakharov
  1 sibling, 0 replies; 5+ messages in thread
From: Aleksei Zakharov @ 2019-12-09 13:58 UTC (permalink / raw)
  To: linux-block; +Cc: Aleksei Zakharov

BIO_SPLITTED flag will be used to gather statistics for
splitted bio's.
---
 include/linux/blk_types.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 70254ae11769..7ff32e7c48fb 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -148,7 +148,7 @@ struct bio {
 						 * top bits REQ_OP. Use
 						 * accessors.
 						 */
-	unsigned short		bi_flags;	/* status, etc and bvec pool number */
+	unsigned int		bi_flags;	/* status, etc and bvec pool number */
 	unsigned short		bi_ioprio;
 	unsigned short		bi_write_hint;
 	blk_status_t		bi_status;
@@ -207,6 +207,7 @@ struct bio {
  * bio flags
  */
 enum {
+	BIO_SPLITTED,		/* set if bio was split in bio_split */
 	BIO_NO_PAGE_REF,	/* don't put release vec pages */
 	BIO_CLONED,		/* doesn't own data */
 	BIO_BOUNCED,		/* bio is a bounce bio */
@@ -240,7 +241,7 @@ enum {
  * freed.
  */
 #define BVEC_POOL_BITS		(3)
-#define BVEC_POOL_OFFSET	(16 - BVEC_POOL_BITS)
+#define BVEC_POOL_OFFSET	(32 - BVEC_POOL_BITS)
 #define BVEC_POOL_IDX(bio)	((bio)->bi_flags >> BVEC_POOL_OFFSET)
 #if (1<< BVEC_POOL_BITS) < (BVEC_POOL_NR+1)
 # error "BVEC_POOL_BITS is too small"
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 5+ messages in thread
* [PATCH 2/2] block: add iostat counters for requests splits
  2019-12-09 13:57 [PATCH 0/2] block: add bio split counters for iostat Aleksei Zakharov
  2019-12-09 13:58 ` [PATCH 1/2] block: extend bi_flags to int and introduce BIO_SPLITTED Aleksei Zakharov
@ 2019-12-09 13:58 ` Aleksei Zakharov
  2019-12-10  3:08   ` Ming Lei
  1 sibling, 1 reply; 5+ messages in thread
From: Aleksei Zakharov @ 2019-12-09 13:58 UTC (permalink / raw)
  To: linux-block; +Cc: Aleksei Zakharov

I/O request can be splitted for two or more requests,
if it's size is greater than queue/max_sectors_kb
setting.

Knowledge of splits frequency helps to understand workload
profile better and to make decision to tune queue/max_sectors_kb.

This patch adds three counters to /sys/class/block/$dev/stat
and /proc/diskstats: number of reads, writes and discards
splitted.

There's also counter for flush requests, but it is ignored,
because flush cannot be splitted.
---
 Documentation/ABI/testing/procfs-diskstats |  3 +++
 Documentation/ABI/testing/sysfs-block      |  5 ++++-
 Documentation/admin-guide/iostats.rst      | 10 ++++++++++
 block/bio.c                                |  2 ++
 block/blk-core.c                           |  2 ++
 block/genhd.c                              |  8 ++++++--
 block/partition-generic.c                  |  8 ++++++--
 include/linux/genhd.h                      |  1 +
 8 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/Documentation/ABI/testing/procfs-diskstats b/Documentation/ABI/testing/procfs-diskstats
index 70dcaf2481f4..e1473e93d901 100644
--- a/Documentation/ABI/testing/procfs-diskstats
+++ b/Documentation/ABI/testing/procfs-diskstats
@@ -33,5 +33,8 @@ Description:
 
 		19 - flush requests completed successfully
 		20 - time spent flushing
+		21 - reads splitted
+		22 - writes splitted
+		23 - discards splitted
 
 		For more details refer to Documentation/admin-guide/iostats.rst
diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index ed8c14f161ee..ffbac0e72508 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -3,7 +3,7 @@ Date:		February 2008
 Contact:	Jerome Marchand <jmarchan@redhat.com>
 Description:
 		The /sys/block/<disk>/stat files displays the I/O
-		statistics of disk <disk>. They contain 11 fields:
+		statistics of disk <disk>. They contain 20 fields:
 		 1 - reads completed successfully
 		 2 - reads merged
 		 3 - sectors read
@@ -21,6 +21,9 @@ Description:
 		15 - time spent discarding (ms)
 		16 - flush requests completed
 		17 - time spent flushing (ms)
+		18 - reads splitted
+		19 - writes splitted
+		20 - discrads splitted
 		For more details refer Documentation/admin-guide/iostats.rst
 
 
diff --git a/Documentation/admin-guide/iostats.rst b/Documentation/admin-guide/iostats.rst
index 4f0462af3ca7..7f3f374b82b7 100644
--- a/Documentation/admin-guide/iostats.rst
+++ b/Documentation/admin-guide/iostats.rst
@@ -130,6 +130,16 @@ Field 16 -- # of flush requests completed
 Field 17 -- # of milliseconds spent flushing
     This is the total number of milliseconds spent by all flush requests.
 
+Field 18 -- # of reads splitted, field 19 -- # of writes splitted
+    This is the total number of requests splitted before queue.
+
+    The maximum size of I/O is limited by queue/max_sectors_kb.
+    If size of I/O is greater than this limit, it will be splitted
+    as many times as needed to keep I/O size withing the limit.
+
+Field 20 -- # of discrads Splitted
+    See description of fileds 18 and 19.
+
 To avoid introducing performance bottlenecks, no locks are held while
 modifying these counters.  This implies that minor inaccuracies may be
 introduced when changes collide, so (for instance) adding up all the
diff --git a/block/bio.c b/block/bio.c
index 8f0ed6228fc5..c8a051e128f8 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1855,6 +1855,8 @@ struct bio *bio_split(struct bio *bio, int sectors,
 	if (bio_flagged(bio, BIO_TRACE_COMPLETION))
 		bio_set_flag(split, BIO_TRACE_COMPLETION);
 
+	bio_set_flag(split, BIO_SPLITTED);
+
 	return split;
 }
 EXPORT_SYMBOL(bio_split);
diff --git a/block/blk-core.c b/block/blk-core.c
index f0d82227a2fc..776d28b9a5bf 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1379,6 +1379,8 @@ void blk_account_io_start(struct request *rq, bool new_io)
 		}
 		part_inc_in_flight(rq->q, part, rw);
 		rq->part = part;
+		if (bio_flagged(rq->bio, BIO_SPLITTED))
+			part_stat_inc(part, splits[rw]);
 	}
 
 	update_io_ticks(part, jiffies);
diff --git a/block/genhd.c b/block/genhd.c
index ff6268970ddc..adb38baa24dc 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1386,7 +1386,8 @@ static int diskstats_show(struct seq_file *seqf, void *v)
 			   "%lu %lu %lu %u "
 			   "%u %u %u "
 			   "%lu %lu %lu %u "
-			   "%lu %u"
+			   "%lu %u "
+			   "%lu %lu %lu"
 			   "\n",
 			   MAJOR(part_devt(hd)), MINOR(part_devt(hd)),
 			   disk_name(gp, hd->partno, buf),
@@ -1406,7 +1407,10 @@ static int diskstats_show(struct seq_file *seqf, void *v)
 			   part_stat_read(hd, sectors[STAT_DISCARD]),
 			   (unsigned int)part_stat_read_msecs(hd, STAT_DISCARD),
 			   part_stat_read(hd, ios[STAT_FLUSH]),
-			   (unsigned int)part_stat_read_msecs(hd, STAT_FLUSH)
+			   (unsigned int)part_stat_read_msecs(hd, STAT_FLUSH),
+			   part_stat_read(hd, splits[STAT_READ]),
+			   part_stat_read(hd, splits[STAT_WRITE]),
+			   part_stat_read(hd, splits[STAT_DISCARD])
 			);
 	}
 	disk_part_iter_exit(&piter);
diff --git a/block/partition-generic.c b/block/partition-generic.c
index 3db8b73a96b1..61e26ec21256 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -128,7 +128,8 @@ ssize_t part_stat_show(struct device *dev,
 		"%8lu %8lu %8llu %8u "
 		"%8u %8u %8u "
 		"%8lu %8lu %8llu %8u "
-		"%8lu %8u"
+		"%8lu %8u "
+		"%8lu %8lu %8lu"
 		"\n",
 		part_stat_read(p, ios[STAT_READ]),
 		part_stat_read(p, merges[STAT_READ]),
@@ -146,7 +147,10 @@ ssize_t part_stat_show(struct device *dev,
 		(unsigned long long)part_stat_read(p, sectors[STAT_DISCARD]),
 		(unsigned int)part_stat_read_msecs(p, STAT_DISCARD),
 		part_stat_read(p, ios[STAT_FLUSH]),
-		(unsigned int)part_stat_read_msecs(p, STAT_FLUSH));
+		(unsigned int)part_stat_read_msecs(p, STAT_FLUSH),
+		part_stat_read(p, splits[STAT_READ]),
+		part_stat_read(p, splits[STAT_WRITE]),
+		part_stat_read(p, splits[STAT_DISCARD]));
 }
 
 ssize_t part_inflight_show(struct device *dev, struct device_attribute *attr,
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 8b5330dd5ac0..ea502e7b12b6 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -88,6 +88,7 @@ struct disk_stats {
 	unsigned long sectors[NR_STAT_GROUPS];
 	unsigned long ios[NR_STAT_GROUPS];
 	unsigned long merges[NR_STAT_GROUPS];
+	unsigned long splits[NR_STAT_GROUPS];
 	unsigned long io_ticks;
 	unsigned long time_in_queue;
 	local_t in_flight[2];
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] block: add iostat counters for requests splits
  2019-12-09 13:58 ` [PATCH 2/2] block: add iostat counters for requests splits Aleksei Zakharov
@ 2019-12-10  3:08   ` Ming Lei
  2019-12-10 13:39     ` Aleksei Zakharov
  0 siblings, 1 reply; 5+ messages in thread
From: Ming Lei @ 2019-12-10  3:08 UTC (permalink / raw)
  To: Aleksei Zakharov; +Cc: linux-block

On Mon, Dec 9, 2019 at 10:25 PM Aleksei Zakharov <zaharov@selectel.ru> wrote:
>
> I/O request can be splitted for two or more requests,
> if it's size is greater than queue/max_sectors_kb
> setting.
>
> Knowledge of splits frequency helps to understand workload
> profile better and to make decision to tune queue/max_sectors_kb.

IO split should be one static behavior, so if one bio's sector/size is provided,
it is easy to figure out the split pattern, not sure if it is worth of
adding statistics
in iostat.

That said the IO split analysis can be done simply as post-process of IO trace,
or even it can be done runtime via bcc/bpftrace script without much difficulty.

>
> This patch adds three counters to /sys/class/block/$dev/stat
> and /proc/diskstats: number of reads, writes and discards
> splitted.
>
> There's also counter for flush requests, but it is ignored,
> because flush cannot be splitted.
> ---
>  Documentation/ABI/testing/procfs-diskstats |  3 +++
>  Documentation/ABI/testing/sysfs-block      |  5 ++++-
>  Documentation/admin-guide/iostats.rst      | 10 ++++++++++
>  block/bio.c                                |  2 ++
>  block/blk-core.c                           |  2 ++
>  block/genhd.c                              |  8 ++++++--
>  block/partition-generic.c                  |  8 ++++++--
>  include/linux/genhd.h                      |  1 +
>  8 files changed, 34 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/ABI/testing/procfs-diskstats b/Documentation/ABI/testing/procfs-diskstats
> index 70dcaf2481f4..e1473e93d901 100644
> --- a/Documentation/ABI/testing/procfs-diskstats
> +++ b/Documentation/ABI/testing/procfs-diskstats
> @@ -33,5 +33,8 @@ Description:
>
>                 19 - flush requests completed successfully
>                 20 - time spent flushing
> +               21 - reads splitted
> +               22 - writes splitted
> +               23 - discards splitted
>
>                 For more details refer to Documentation/admin-guide/iostats.rst
> diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
> index ed8c14f161ee..ffbac0e72508 100644
> --- a/Documentation/ABI/testing/sysfs-block
> +++ b/Documentation/ABI/testing/sysfs-block
> @@ -3,7 +3,7 @@ Date:           February 2008
>  Contact:       Jerome Marchand <jmarchan@redhat.com>
>  Description:
>                 The /sys/block/<disk>/stat files displays the I/O
> -               statistics of disk <disk>. They contain 11 fields:
> +               statistics of disk <disk>. They contain 20 fields:
>                  1 - reads completed successfully
>                  2 - reads merged
>                  3 - sectors read
> @@ -21,6 +21,9 @@ Description:
>                 15 - time spent discarding (ms)
>                 16 - flush requests completed
>                 17 - time spent flushing (ms)
> +               18 - reads splitted
> +               19 - writes splitted
> +               20 - discrads splitted
>                 For more details refer Documentation/admin-guide/iostats.rst
>
>
> diff --git a/Documentation/admin-guide/iostats.rst b/Documentation/admin-guide/iostats.rst
> index 4f0462af3ca7..7f3f374b82b7 100644
> --- a/Documentation/admin-guide/iostats.rst
> +++ b/Documentation/admin-guide/iostats.rst
> @@ -130,6 +130,16 @@ Field 16 -- # of flush requests completed
>  Field 17 -- # of milliseconds spent flushing
>      This is the total number of milliseconds spent by all flush requests.
>
> +Field 18 -- # of reads splitted, field 19 -- # of writes splitted
> +    This is the total number of requests splitted before queue.
> +
> +    The maximum size of I/O is limited by queue/max_sectors_kb.
> +    If size of I/O is greater than this limit, it will be splitted
> +    as many times as needed to keep I/O size withing the limit.
> +
> +Field 20 -- # of discrads Splitted
> +    See description of fileds 18 and 19.
> +
>  To avoid introducing performance bottlenecks, no locks are held while
>  modifying these counters.  This implies that minor inaccuracies may be
>  introduced when changes collide, so (for instance) adding up all the
> diff --git a/block/bio.c b/block/bio.c
> index 8f0ed6228fc5..c8a051e128f8 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1855,6 +1855,8 @@ struct bio *bio_split(struct bio *bio, int sectors,
>         if (bio_flagged(bio, BIO_TRACE_COMPLETION))
>                 bio_set_flag(split, BIO_TRACE_COMPLETION);
>
> +       bio_set_flag(split, BIO_SPLITTED);
> +
>         return split;
>  }
>  EXPORT_SYMBOL(bio_split);
> diff --git a/block/blk-core.c b/block/blk-core.c
> index f0d82227a2fc..776d28b9a5bf 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1379,6 +1379,8 @@ void blk_account_io_start(struct request *rq, bool new_io)
>                 }
>                 part_inc_in_flight(rq->q, part, rw);
>                 rq->part = part;
> +               if (bio_flagged(rq->bio, BIO_SPLITTED))
> +                       part_stat_inc(part, splits[rw]);

It is the only use of BIO_SPLITTED, and it should have been done as one rq flag,
then extra change in bio struct can be avoided.  If the bio is
splitted can be easily
figured out in blk_mq_make_request(),  then you may pass that info to
blk_mq_bio_to_request().

Thanks,
Ming

^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] block: add iostat counters for requests splits
  2019-12-10  3:08   ` Ming Lei
@ 2019-12-10 13:39     ` Aleksei Zakharov
  0 siblings, 0 replies; 5+ messages in thread
From: Aleksei Zakharov @ 2019-12-10 13:39 UTC (permalink / raw)
  To: Ming Lei; +Cc: linux-block

вт, 10 дек. 2019 г. в 06:09, Ming Lei <tom.leiming@gmail.com>:
>
> On Mon, Dec 9, 2019 at 10:25 PM Aleksei Zakharov <zaharov@selectel.ru> wrote:
> >
> > I/O request can be splitted for two or more requests,
> > if it's size is greater than queue/max_sectors_kb
> > setting.
> >
> > Knowledge of splits frequency helps to understand workload
> > profile better and to make decision to tune queue/max_sectors_kb.
>
> IO split should be one static behavior, so if one bio's sector/size is provided,
> it is easy to figure out the split pattern, not sure if it is worth of
> adding statistics
> in iostat.
>
> That said the IO split analysis can be done simply as post-process of IO trace,
> or even it can be done runtime via bcc/bpftrace script without much difficulty.
Yes, you're right, it can be done via bpftrace. But iostat is just well-known
and overall used tool. It's better to have most of stats with default tool,
than have a lot of tools for different parts of one subsystem layer, IMO.

>
> >
> > This patch adds three counters to /sys/class/block/$dev/stat
> > and /proc/diskstats: number of reads, writes and discards
> > splitted.
> >
> > There's also counter for flush requests, but it is ignored,
> > because flush cannot be splitted.
> > ---
> >  Documentation/ABI/testing/procfs-diskstats |  3 +++
> >  Documentation/ABI/testing/sysfs-block      |  5 ++++-
> >  Documentation/admin-guide/iostats.rst      | 10 ++++++++++
> >  block/bio.c                                |  2 ++
> >  block/blk-core.c                           |  2 ++
> >  block/genhd.c                              |  8 ++++++--
> >  block/partition-generic.c                  |  8 ++++++--
> >  include/linux/genhd.h                      |  1 +
> >  8 files changed, 34 insertions(+), 5 deletions(-)
> >
> > diff --git a/Documentation/ABI/testing/procfs-diskstats b/Documentation/ABI/testing/procfs-diskstats
> > index 70dcaf2481f4..e1473e93d901 100644
> > --- a/Documentation/ABI/testing/procfs-diskstats
> > +++ b/Documentation/ABI/testing/procfs-diskstats
> > @@ -33,5 +33,8 @@ Description:
> >
> >                 19 - flush requests completed successfully
> >                 20 - time spent flushing
> > +               21 - reads splitted
> > +               22 - writes splitted
> > +               23 - discards splitted
> >
> >                 For more details refer to Documentation/admin-guide/iostats.rst
> > diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
> > index ed8c14f161ee..ffbac0e72508 100644
> > --- a/Documentation/ABI/testing/sysfs-block
> > +++ b/Documentation/ABI/testing/sysfs-block
> > @@ -3,7 +3,7 @@ Date:           February 2008
> >  Contact:       Jerome Marchand <jmarchan@redhat.com>
> >  Description:
> >                 The /sys/block/<disk>/stat files displays the I/O
> > -               statistics of disk <disk>. They contain 11 fields:
> > +               statistics of disk <disk>. They contain 20 fields:
> >                  1 - reads completed successfully
> >                  2 - reads merged
> >                  3 - sectors read
> > @@ -21,6 +21,9 @@ Description:
> >                 15 - time spent discarding (ms)
> >                 16 - flush requests completed
> >                 17 - time spent flushing (ms)
> > +               18 - reads splitted
> > +               19 - writes splitted
> > +               20 - discrads splitted
> >                 For more details refer Documentation/admin-guide/iostats.rst
> >
> >
> > diff --git a/Documentation/admin-guide/iostats.rst b/Documentation/admin-guide/iostats.rst
> > index 4f0462af3ca7..7f3f374b82b7 100644
> > --- a/Documentation/admin-guide/iostats.rst
> > +++ b/Documentation/admin-guide/iostats.rst
> > @@ -130,6 +130,16 @@ Field 16 -- # of flush requests completed
> >  Field 17 -- # of milliseconds spent flushing
> >      This is the total number of milliseconds spent by all flush requests.
> >
> > +Field 18 -- # of reads splitted, field 19 -- # of writes splitted
> > +    This is the total number of requests splitted before queue.
> > +
> > +    The maximum size of I/O is limited by queue/max_sectors_kb.
> > +    If size of I/O is greater than this limit, it will be splitted
> > +    as many times as needed to keep I/O size withing the limit.
> > +
> > +Field 20 -- # of discrads Splitted
> > +    See description of fileds 18 and 19.
> > +
> >  To avoid introducing performance bottlenecks, no locks are held while
> >  modifying these counters.  This implies that minor inaccuracies may be
> >  introduced when changes collide, so (for instance) adding up all the
> > diff --git a/block/bio.c b/block/bio.c
> > index 8f0ed6228fc5..c8a051e128f8 100644
> > --- a/block/bio.c
> > +++ b/block/bio.c
> > @@ -1855,6 +1855,8 @@ struct bio *bio_split(struct bio *bio, int sectors,
> >         if (bio_flagged(bio, BIO_TRACE_COMPLETION))
> >                 bio_set_flag(split, BIO_TRACE_COMPLETION);
> >
> > +       bio_set_flag(split, BIO_SPLITTED);
> > +
> >         return split;
> >  }
> >  EXPORT_SYMBOL(bio_split);
> > diff --git a/block/blk-core.c b/block/blk-core.c
> > index f0d82227a2fc..776d28b9a5bf 100644
> > --- a/block/blk-core.c
> > +++ b/block/blk-core.c
> > @@ -1379,6 +1379,8 @@ void blk_account_io_start(struct request *rq, bool new_io)
> >                 }
> >                 part_inc_in_flight(rq->q, part, rw);
> >                 rq->part = part;
> > +               if (bio_flagged(rq->bio, BIO_SPLITTED))
> > +                       part_stat_inc(part, splits[rw]);
>
> It is the only use of BIO_SPLITTED, and it should have been done as one rq flag,
> then extra change in bio struct can be avoided.  If the bio is
> splitted can be easily
> figured out in blk_mq_make_request(),  then you may pass that info to
> blk_mq_bio_to_request().
Thanks for pointing that out!
I'll rethink this patch.
>
> Thanks,
> Ming



-- 
Best Regards,
Aleksei Zakharov
System administrator

www.selectel.com

^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2019-12-10 13:39 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-12-09 13:57 [PATCH 0/2] block: add bio split counters for iostat Aleksei Zakharov
2019-12-09 13:58 ` [PATCH 1/2] block: extend bi_flags to int and introduce BIO_SPLITTED Aleksei Zakharov
2019-12-09 13:58 ` [PATCH 2/2] block: add iostat counters for requests splits Aleksei Zakharov
2019-12-10  3:08   ` Ming Lei
2019-12-10 13:39     ` Aleksei Zakharov

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