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
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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
compatfd.c
coroutine-sigaltstack.c
coroutine-ucontext.c
coroutine-windows.c
cpuinfo-aarch64.c
cpuinfo-i386.c
cpuinfo-ppc.c
crc32c.c
crc-ccitt.c
cutils.c
dbus.c
defer-call.c
drm.c
envlist.c
error-report.c
error.c
event_notifier-posix.c
event_notifier-win32.c
fdmon-epoll.c
fdmon-io_uring.c
fdmon-poll.c
fifo8.c
filemonitor-inotify.c
filemonitor-stub.c
getauxval.c
guest-random.c
hbitmap.c
hexdump.c
host-utils.c
id.c
int128.c
interval-tree.c
iov.c
iova-tree.c
keyval.c
lockcnt.c
log.c
main-loop.c
memalign.c
memfd.c
meson.build
mmap-alloc.c
module.c
notify.c
nvdimm-utils.c
osdep.c
oslib-posix.c
oslib-win32.c
path.c
qdist.c
qemu-co-shared-resource.c
qemu-co-timeout.c
qemu-config.c
qemu-coroutine-io.c
qemu-coroutine-lock.c
qemu-coroutine-sleep.c
qemu-coroutine.c
qemu-option.c
qemu-print.c
qemu-progress.c
qemu-sockets.c
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
readline.c
selfmap.c
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
timed-average.c
trace-events
trace.h
transactions.c
unicode.c
uri.c
userfaultfd.c
uuid.c
vfio-helpers.c
vhost-user-server.c
yank.c