Maxim Levitsky 867eccfed8 file-posix: Use max transfer length/segment count only for SCSI passthrough ... Regular kernel block devices (/dev/sda*, /dev/nvme*, etc) don't have max segment size/max segment count hardware requirements exposed to the userspace, but rather the kernel block layer takes care to split the incoming requests that violate these requirements. Allowing the kernel to do the splitting allows qemu to avoid various overheads that arise otherwise from this. This is especially visible in nbd server, exposing as a raw file, a mostly empty qcow2 image over the net. In this case most of the reads by the remote user won't even hit the underlying kernel block device, and therefore most of the overhead will be in the nbd traffic which increases significantly with lower max transfer size. In addition to that even for local block device access the peformance improves a bit due to less traffic between qemu and the kernel when large transfer sizes are used (e.g for image conversion) More info can be found at: https://bugzilla.redhat.com/show_bug.cgi?id=1647104 Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Pankaj Gupta <pagupta@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>		2019-07-12 15:42:23 +02:00
..
accounting.c	block/accounting: introduce latency histogram	2018-03-19 14:58:37 -05:00
backup.c	block: Add BlockBackend.ctx	2019-06-04 15:22:22 +02:00
blkdebug.c	blkdebug: Inject errors on .bdrv_co_block_status()	2019-06-14 14:16:57 +02:00
blklogwrites.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
blkreplay.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
blkverify.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
block-backend.c	block/block-backend: blk_iostatus_reset: drop usage of bs->job	2019-06-18 16:41:10 +02:00
bochs.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
cloop.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
commit.c	block: include base when checking image chain for block allocation	2019-07-02 03:53:04 +02:00
copy-on-read.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
create.c	jobs: utilize job_exit shim	2018-08-31 16:28:33 +02:00
crypto.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
crypto.h	Clean up ill-advised or unusual header guards	2019-05-13 08:58:55 +02:00
curl.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
dirty-bitmap.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
dmg-bz2.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
dmg-lzfse.c	block: adding lzfse decompressing support as a module.	2018-12-14 11:52:40 +01:00
dmg.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
dmg.h	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
file-posix.c	file-posix: Use max transfer length/segment count only for SCSI passthrough	2019-07-12 15:42:23 +02:00
file-win32.c	avoid TABs in files that only contain a few	2019-01-11 15:46:56 +01:00
gluster.c	block/gluster: update .help of BLOCK_OPT_PREALLOC option	2019-06-12 18:32:32 +02:00
io.c	block: include base when checking image chain for block allocation	2019-07-02 03:53:04 +02:00
iscsi-opts.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
iscsi.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
linux-aio.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
Makefile.objs	ssh: switch from libssh2 to libssh	2019-06-24 16:01:04 +02:00
mirror.c	block: include base when checking image chain for block allocation	2019-07-02 03:53:04 +02:00
nbd.c	block/nbd: merge NBDClientSession struct back to BDRVNBDState	2019-06-13 10:00:42 -05:00
nfs.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
null.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
nvme.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
parallels.c	block: Add BlockBackend.ctx	2019-06-04 15:22:22 +02:00
parallels.h	Clean up includes	2018-02-09 05:05:11 +01:00
qapi.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
qcow.c	block/qcow: Improve error when opening qcow2 files as qcow	2019-07-08 16:00:26 +02:00
qcow2-bitmap.c	qcow2-bitmap: initialize bitmap directory alignment	2019-05-28 20:30:55 +02:00
qcow2-cache.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
qcow2-cluster.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
qcow2-refcount.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
qcow2-snapshot.c	qcow2.h: add missing include	2019-05-28 20:30:55 +02:00
qcow2-threads.c	qcow2: do encryption in threads	2019-05-28 20:30:55 +02:00
qcow2.c	qcow2: Allow -o compat=v3 during qemu-img amend	2019-07-08 16:00:31 +02:00
qcow2.h	block: avoid recursive block_status call if possible	2019-06-04 15:20:41 +02:00
qed-check.c	block/qed: add missed coroutine_fn markers	2019-04-30 15:29:00 +02:00
qed-cluster.c	qed: protect table cache with CoMutex	2017-07-17 11:34:11 +08:00
qed-l2-cache.c	qed: protect table cache with CoMutex	2017-07-17 11:34:11 +08:00
qed-table.c	block/qed: add missed coroutine_fn markers	2019-04-30 15:29:00 +02:00
qed.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
qed.h	block/qed: add missed coroutine_fn markers	2019-04-30 15:29:00 +02:00
quorum.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
raw-format.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
rbd.c	block/rbd: increase dynamically the image size	2019-07-02 03:53:04 +02:00
replication.c	block: include base when checking image chain for block allocation	2019-07-02 03:53:04 +02:00
sheepdog.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
snapshot.c	block/snapshot: remove bdrv_snapshot_delete_by_id_or_name	2019-02-25 15:03:18 +01:00
ssh.c	ssh: switch from libssh2 to libssh	2019-06-24 16:01:04 +02:00
stream.c	block/stream: introduce a bottom node	2019-07-02 03:53:05 +02:00
throttle-groups.c	throttle-groups: fix restart coroutine iothread race	2019-01-24 10:02:28 +00:00
throttle.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
trace-events	ssh: switch from libssh2 to libssh	2019-06-24 16:01:04 +02:00
vdi.c	block: Add BlockBackend.ctx	2019-06-04 15:22:22 +02:00
vhdx-endian.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
vhdx-log.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
vhdx.c	block: Add BlockBackend.ctx	2019-06-04 15:22:22 +02:00
vhdx.h	block/vhdx: Use IEC binary prefixes for size constants	2019-04-30 15:29:00 +02:00
vmdk.c	vmdk: Add read-only support for seSparse snapshots	2019-06-24 15:53:02 +02:00
vpc.c	block: Add BlockBackend.ctx	2019-06-04 15:22:22 +02:00
vvfat.c	qemu-common: Move qemu_isalnum() etc. to qemu/ctype.h	2019-06-11 20:22:09 +02:00
vxhs.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
win32-aio.c	Include qemu/module.h where needed, drop it from qemu-common.h	2019-06-12 13:18:33 +02:00
write-threshold.c	qapi: Drop qapi_event_send_FOO()'s Error ** argument	2018-08-28 18:21:38 +02:00