qemu-e2k/util
Stefan Hajnoczi 84d61e5f36 virtio: use defer_call() in virtio_irqfd_notify()
virtio-blk and virtio-scsi invoke virtio_irqfd_notify() to send Used
Buffer Notifications from an IOThread. This involves an eventfd
write(2) syscall. Calling this repeatedly when completing multiple I/O
requests in a row is wasteful.

Use the defer_call() API to batch together virtio_irqfd_notify() calls
made during thread pool (aio=threads), Linux AIO (aio=native), and
io_uring (aio=io_uring) completion processing.

Behavior is unchanged for emulated devices that do not use
defer_call_begin()/defer_call_end() since defer_call() immediately
invokes the callback when called outside a
defer_call_begin()/defer_call_end() region.

fio rw=randread bs=4k iodepth=64 numjobs=8 IOPS increases by ~9% with a
single IOThread and 8 vCPUs. iodepth=1 decreases by ~1% but this could
be noise. Detailed performance data and configuration specifics are
available here:
https://gitlab.com/stefanha/virt-playbooks/-/tree/blk_io_plug-irqfd

This duplicates the BH that virtio-blk uses for batching. The next
commit will remove it.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230913200045.1024233-4-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-10-31 15:42:14 +01:00
..
aio-posix.c
aio-posix.h
aio-wait.c
aio-win32.c
aiocb.c
async.c
atomic64.c
base64.c
bitmap.c
bitops.c
block-helpers.c
block-helpers.h
buffer.c
bufferiszero.c
cacheflush.c util/cacheflush: Avoid possible redundant dcache flush on Darwin 2023-06-13 11:28:58 +02:00
compatfd.c
coroutine-sigaltstack.c osdep: set _FORTIFY_SOURCE=2 when optimization is enabled 2023-10-04 09:52:06 -04:00
coroutine-ucontext.c osdep: set _FORTIFY_SOURCE=2 when optimization is enabled 2023-10-04 09:52:06 -04:00
coroutine-windows.c
cpuinfo-aarch64.c *: Delete checks for old host definitions 2023-09-19 13:20:54 -04:00
cpuinfo-i386.c host/include/i386: Implement clmul.h 2023-09-15 13:57:00 +00:00
cpuinfo-ppc.c util: spelling fixes 2023-08-31 19:47:43 +02:00
crc32c.c
crc-ccitt.c
cutils.c cutils: Fix get_relocated_path on Windows 2023-10-19 23:13:27 +02:00
dbus.c
defer-call.c util/defer-call: move defer_call() to util/ 2023-10-31 15:41:42 +01:00
drm.c
envlist.c
error-report.c
error.c
event_notifier-posix.c
event_notifier-win32.c
fdmon-epoll.c
fdmon-io_uring.c aio-posix: zero out io_uring sqe user_data 2023-08-30 07:39:59 -04:00
fdmon-poll.c
fifo8.c
filemonitor-inotify.c
filemonitor-stub.c
getauxval.c
guest-random.c util/guest-random: Clean up global variable shadowing 2023-10-06 13:27:48 +02:00
hbitmap.c
hexdump.c
host-utils.c
id.c
int128.c
interval-tree.c util/interval-tree: Check root for null in interval_tree_iter_first 2023-08-09 09:26:32 -07:00
iov.c util/iov: Avoid dynamic stack allocation 2023-09-07 20:32:11 -05:00
iova-tree.c
keyval.c
lockcnt.c
log.c util/log: re-allow switching away from stderr log file 2023-10-07 19:02:33 +02:00
main-loop.c util: spelling fixes 2023-08-31 19:47:43 +02:00
memalign.c
memfd.c
meson.build util/defer-call: move defer_call() to util/ 2023-10-31 15:41:42 +01:00
mmap-alloc.c
module.c
notify.c
nvdimm-utils.c
osdep.c
oslib-posix.c util: Delete checks for old host definitions 2023-09-15 05:26:50 -07:00
oslib-win32.c win32: avoid discarding the exception handler 2023-10-03 15:05:20 +04:00
path.c
qdist.c util: spelling fixes 2023-08-31 19:47:43 +02:00
qemu-co-shared-resource.c
qemu-co-timeout.c
qemu-config.c
qemu-coroutine-io.c
qemu-coroutine-lock.c atomics: eliminate mb_read/mb_set 2023-06-06 09:42:14 +02:00
qemu-coroutine-sleep.c
qemu-coroutine.c meson: do not use set10 2023-10-17 15:20:53 +02:00
qemu-option.c
qemu-print.c
qemu-progress.c
qemu-sockets.c util: spelling fixes 2023-08-31 19:47:43 +02:00
qemu-thread-common.h
qemu-thread-posix.c
qemu-thread-win32.c
qemu-timer-common.c
qemu-timer.c
qht.c
qsp.c
qtree.c
range.c
rcu.c util: spelling fixes 2023-08-31 19:47:43 +02:00
readline.c
selfmap.c util/selfmap: Use dev_t and ino_t in MapInfo 2023-09-01 13:34:03 -07:00
stats64.c
sys_membarrier.c
systemd.c
thread-context.c
thread-pool.c virtio: use defer_call() in virtio_irqfd_notify() 2023-10-31 15:42:14 +01:00
throttle.c throttle: use THROTTLE_MAX/ARRAY_SIZE for hard code 2023-08-29 10:49:24 +02:00
timed-average.c
trace-events console/win32: allocate shareable display surface 2023-06-27 17:08:56 +02:00
trace.h
transactions.c
unicode.c
uri.c
userfaultfd.c
uuid.c util/uuid: add a hash function 2023-10-04 18:15:06 -04:00
vfio-helpers.c
vhost-user-server.c util/vhost-user-server: Clean up local variable shadowing 2023-09-29 10:07:16 +02:00
yank.c