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/lib/libspl/Makefile.in b/lib/libspl/Makefile.in
index 4db8c3553..b77af2300 100644
--- a/lib/libspl/Makefile.in
+++ b/lib/libspl/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/lib/libspl/asm-generic/Makefile.in b/lib/libspl/asm-generic/Makefile.in
index f838c9101..7fb66ef7c 100644
--- a/lib/libspl/asm-generic/Makefile.in
+++ b/lib/libspl/asm-generic/Makefile.in
@@ -51,6 +51,11 @@ 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/lib/libspl/asm-i386/Makefile.in b/lib/libspl/asm-i386/Makefile.in
index 4d8e4502c..bf418b90e 100644
--- a/lib/libspl/asm-i386/Makefile.in
+++ b/lib/libspl/asm-i386/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/lib/libspl/asm-x86_64/Makefile.in b/lib/libspl/asm-x86_64/Makefile.in
index 9edbecf39..2d6f74644 100644
--- a/lib/libspl/asm-x86_64/Makefile.in
+++ b/lib/libspl/asm-x86_64/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/lib/libspl/include/Makefile.in b/lib/libspl/include/Makefile.in
index c04faa5fc..9c693d43f 100644
--- a/lib/libspl/include/Makefile.in
+++ b/lib/libspl/include/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/lib/libspl/include/ia32/Makefile.in b/lib/libspl/include/ia32/Makefile.in
index eeccf56a0..789214e5f 100644
--- a/lib/libspl/include/ia32/Makefile.in
+++ b/lib/libspl/include/ia32/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/lib/libspl/include/ia32/sys/Makefile.in b/lib/libspl/include/ia32/sys/Makefile.in
index 246f71995..058f143a5 100644
--- a/lib/libspl/include/ia32/sys/Makefile.in
+++ b/lib/libspl/include/ia32/sys/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/lib/libspl/include/rpc/Makefile.in b/lib/libspl/include/rpc/Makefile.in
index d70ce7034..840100f75 100644
--- a/lib/libspl/include/rpc/Makefile.in
+++ b/lib/libspl/include/rpc/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/lib/libspl/include/sys/Makefile.in b/lib/libspl/include/sys/Makefile.in
index 201b17977..81d011e1a 100644
--- a/lib/libspl/include/sys/Makefile.in
+++ b/lib/libspl/include/sys/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/lib/libspl/include/sys/dktp/Makefile.in b/lib/libspl/include/sys/dktp/Makefile.in
index bbbd4596a..1107586e4 100644
--- a/lib/libspl/include/sys/dktp/Makefile.in
+++ b/lib/libspl/include/sys/dktp/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/lib/libspl/include/sys/sysevent/Makefile.in b/lib/libspl/include/sys/sysevent/Makefile.in
index 9a58c5106..065f9dc0e 100644
--- a/lib/libspl/include/sys/sysevent/Makefile.in
+++ b/lib/libspl/include/sys/sysevent/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/lib/libspl/include/util/Makefile.in b/lib/libspl/include/util/Makefile.in
index 94d0d27c8..62db1c83f 100644
--- a/lib/libspl/include/util/Makefile.in
+++ b/lib/libspl/include/util/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 \