Improve ZVOL queue behavior.

The Linux block device queue subsystem exposes a number of configurable
settings described in Linux block/blk-settings.c. The defaults for these
settings are tuned for hard drives, and are not optimized for ZVOLs. Proper
configuration of these options would allow upper layers (I/O scheduler) to
take better decisions about write merging and ordering.

Detailed rationale:

 - max_hw_sectors is set to unlimited (UINT_MAX). zvol_write() is able to
   handle writes of any size, so there's no reason to impose a limit. Let the
   upper layer decide.

 - max_segments and max_segment_size are set to unlimited. zvol_write() will
   copy the requests' contents into a dbuf anyway, so the number and size of
   the segments are irrelevant. Let the upper layer decide.

 - physical_block_size and io_opt are set to the ZVOL's block size. This
   has the potential to somewhat alleviate issue #361 for ZVOLs, by warning
   the upper layers that writes smaller than the volume's block size will be
   slow.

 - The NONROT flag is set to indicate this isn't a rotational device.
   Although the backing zpool might be composed of rotational devices, the
   resulting ZVOL often doesn't exhibit the same behavior due to the COW
   mechanisms used by ZFS. Setting this flag will prevent upper layers from
   making useless decisions (such as reordering writes) based on incorrect
   assumptions about the behavior of the ZVOL.

Signed-off-by: Brian Behlendorf <[email protected]>

12 files changed, 60 insertions, 0 deletions

diff --git a/cmd/Makefile.in b/cmd/Makefile.in
index ba5360941..a0fdde92c 100644
--- a/cmd/Makefile.in
+++ b/cmd/Makefile.in
@@ -50,6 +50,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \
diff --git a/cmd/mount_zfs/Makefile.in b/cmd/mount_zfs/Makefile.in
index 94e316004..350c67dd4 100644
--- a/cmd/mount_zfs/Makefile.in
+++ b/cmd/mount_zfs/Makefile.in
@@ -53,6 +53,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \
diff --git a/cmd/sas_switch_id/Makefile.in b/cmd/sas_switch_id/Makefile.in
index 09826f2c9..94e3a63e6 100644
--- a/cmd/sas_switch_id/Makefile.in
+++ b/cmd/sas_switch_id/Makefile.in
@@ -52,6 +52,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \
diff --git a/cmd/zdb/Makefile.in b/cmd/zdb/Makefile.in
index 7dd5dfc5f..fa0b8c762 100644
--- a/cmd/zdb/Makefile.in
+++ b/cmd/zdb/Makefile.in
@@ -53,6 +53,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \
diff --git a/cmd/zfs/Makefile.in b/cmd/zfs/Makefile.in
index 54f63c75f..ccf9924bd 100644
--- a/cmd/zfs/Makefile.in
+++ b/cmd/zfs/Makefile.in
@@ -53,6 +53,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \
diff --git a/cmd/zinject/Makefile.in b/cmd/zinject/Makefile.in
index 59d67f096..eb3f28d0f 100644
--- a/cmd/zinject/Makefile.in
+++ b/cmd/zinject/Makefile.in
@@ -53,6 +53,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \
diff --git a/cmd/zpios/Makefile.in b/cmd/zpios/Makefile.in
index f357559f3..c9811af10 100644
--- a/cmd/zpios/Makefile.in
+++ b/cmd/zpios/Makefile.in
@@ -53,6 +53,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \
diff --git a/cmd/zpool/Makefile.in b/cmd/zpool/Makefile.in
index cb15fee8e..60a97aa2a 100644
--- a/cmd/zpool/Makefile.in
+++ b/cmd/zpool/Makefile.in
@@ -53,6 +53,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \
diff --git a/cmd/zpool_id/Makefile.in b/cmd/zpool_id/Makefile.in
index a6277ef81..e53c87c4f 100644
--- a/cmd/zpool_id/Makefile.in
+++ b/cmd/zpool_id/Makefile.in
@@ -52,6 +52,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \
diff --git a/cmd/zpool_layout/Makefile.in b/cmd/zpool_layout/Makefile.in
index 12f21e51b..20658364b 100644
--- a/cmd/zpool_layout/Makefile.in
+++ b/cmd/zpool_layout/Makefile.in
@@ -52,6 +52,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \
diff --git a/cmd/ztest/Makefile.in b/cmd/ztest/Makefile.in
index 85fdde032..e95f55cb4 100644
--- a/cmd/ztest/Makefile.in
+++ b/cmd/ztest/Makefile.in
@@ -53,6 +53,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \
diff --git a/cmd/zvol_id/Makefile.in b/cmd/zvol_id/Makefile.in
index 2c22c80dc..39862677f 100644
--- a/cmd/zvol_id/Makefile.in
+++ b/cmd/zvol_id/Makefile.in
@@ -53,6 +53,11 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-blk-end-request.m4 \
 	$(top_srcdir)/config/kernel-blk-fetch-request.m4 \
 	$(top_srcdir)/config/kernel-blk-queue-flush.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-io-opt.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-hw-sectors.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-max-segments.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-nonrot.m4 \
+	$(top_srcdir)/config/kernel-blk-queue-physical-block-size.m4 \
 	$(top_srcdir)/config/kernel-blk-requeue-request.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-bytes.m4 \
 	$(top_srcdir)/config/kernel-blk-rq-pos.m4 \