Chao Gao 816a430c51 util/aio: Defer disabling poll mode as long as possible ... When we measure FIO read performance (cache=writethrough, bs=4k, iodepth=64) in VMs, ~80K/s notifications (e.g., EPT_MISCONFIG) are observed from guest to qemu. It turns out those frequent notificatons are caused by interference from worker threads. Worker threads queue bottom halves after completing IO requests. Pending bottom halves may lead to either aio_compute_timeout() zeros timeout and pass it to try_poll_mode() or run_poll_handlers() returns no progress after noticing pending aio_notify() events. Both cause run_poll_handlers() to call poll_set_started(false) to disable poll mode. However, for both cases, as timeout is already zeroed, the event loop (i.e., aio_poll()) just processes bottom halves and then starts the next event loop iteration. So, disabling poll mode has no value but leads to unnecessary notifications from guest. To minimize unnecessary notifications from guest, defer disabling poll mode to when the event loop is about to be blocked. With this patch applied, FIO seq-read performance (bs=4k, iodepth=64, cache=writethrough) in VMs increases from 330K/s to 413K/s IOPS. Suggested-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Chao Gao <chao.gao@intel.com> Message-id: 20220710120849.63086-1-chao.gao@intel.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>		2023-01-23 15:01:22 -05:00
..
aio-posix.c	util/aio: Defer disabling poll mode as long as possible	2023-01-23 15:01:22 -05:00
aio-posix.h	aio-posix: fix spurious ->poll_ready() callbacks in main loop	2022-03-17 11:23:18 +00:00
aio-wait.c	aio_wait_kick: add missing memory barrier	2022-06-24 17:07:06 +02:00
aio-win32.c	util/aio-win32: Correct the event array size in aio_poll()	2022-11-06 09:48:26 +01:00
aiocb.c
async-teardown.c	os-posix: asynchronous teardown for shutdown on Linux	2022-10-31 09:46:34 +01:00
async.c	coroutine: Use Coroutine typedef name instead of structure tag	2023-01-20 07:23:45 +01:00
atomic64.c	osdep: Move memalign-related functions to their own header	2022-03-07 13:16:49 +00:00
base64.c
bitmap.c	migration: Use non-atomic ops for clear log bitmap	2022-11-21 11:58:10 +01:00
bitops.c
block-helpers.c
block-helpers.h
buffer.c
bufferiszero.c	util/bufferiszero: Use __attribute__((target)) for avx2/avx512	2023-01-16 10:14:12 -10:00
cacheflush.c	util/cacheflush: Optimize flushing when ppc host has coherent icache	2022-06-21 09:28:41 -07:00
compatfd.c	util: replace pipe()+cloexec with g_unix_open_pipe()	2022-05-03 15:18:14 +04:00
coroutine-sigaltstack.c	Remove qemu-common.h include from most units	2022-04-06 14:31:55 +02:00
coroutine-ucontext.c	coroutine-ucontext: use QEMU_DEFINE_STATIC_CO_TLS()	2022-05-04 15:55:23 +02:00
coroutine-win32.c	coroutine-win32: use QEMU_DEFINE_STATIC_CO_TLS()	2022-05-04 15:55:23 +02:00
crc32c.c
crc-ccitt.c
cutils.c	util: remove support for hex numbers with a scaling suffix	2023-01-06 00:51:02 +01:00
dbus.c
drm.c
envlist.c	Use g_new() & friends where that makes obvious sense	2022-03-21 15:44:44 +01:00
error-report.c	util/error: add G_GNUC_PRINTF for various functions	2023-01-11 10:44:34 +01:00
error.c	util/error: add G_GNUC_PRINTF for various functions	2023-01-11 10:44:34 +01:00
event_notifier-posix.c	Replace qemu_pipe() with g_unix_open_pipe()	2022-05-03 15:17:56 +04:00
event_notifier-win32.c	Remove qemu-common.h include from most units	2022-04-06 14:31:55 +02:00
fdmon-epoll.c
fdmon-io_uring.c	aio-posix: fix build failure io_uring 2.2	2022-03-17 11:23:18 +00:00
fdmon-poll.c
fifo8.c
filemonitor-inotify.c
filemonitor-stub.c
getauxval.c
guest-random.c
hbitmap.c	block: simplify handling of try to merge different sized bitmaps	2022-06-24 17:07:06 +02:00
hexdump.c	include: move C/util-related declarations to cutils.h	2022-04-06 14:31:43 +02:00
host-utils.c	host-utils: Implemented signed 256-by-128 division	2022-06-20 08:38:58 -03:00
id.c
int128.c	qemu/int128: addition of div/rem 128-bit operations	2022-01-08 15:46:10 +10:00
interval-tree.c	util: Add interval-tree.c	2022-12-20 17:09:41 -08:00
iov.c	util: make do_send_recv work with partial send/recv	2022-10-12 19:22:01 +04:00
iova-tree.c	util: accept iova_tree_remove_parameter by value	2022-09-02 10:22:39 +08:00
keyval.c	include: add qemu/keyval.h	2022-04-21 17:03:51 +04:00
lockcnt.c
log.c	util/log: Always send errors to logfile when daemonized	2023-01-06 00:50:32 +01:00
main-loop.c	error handling: Use RETRY_ON_EINTR() macro where applicable	2023-01-09 13:50:47 +01:00
memalign.c	osdep: Move memalign-related functions to their own header	2022-03-07 13:16:49 +00:00
memfd.c
meson.build	accel: introduce accelerator blocker API	2023-01-11 09:59:39 +01:00
mmap-alloc.c	util/mmap-alloc: Remove qemu_mempath_getpagesize()	2022-08-26 13:34:21 +02:00
module.c	module: add Error arguments to module_load and module_load_qom	2022-11-06 09:48:50 +01:00
notify.c
nvdimm-utils.c
osdep.c	error handling: Use RETRY_ON_EINTR() macro where applicable	2023-01-09 13:50:47 +01:00
oslib-posix.c	util: Make qemu_prealloc_mem() optionally consume a ThreadContext	2022-10-27 11:00:56 +02:00
oslib-win32.c	util/oslib-win32: Remove obsolete reference to g_poll code	2022-12-15 15:19:24 +01:00
path.c
qdist.c
qemu-co-shared-resource.c
qemu-co-timeout.c	util: add qemu-co-timeout	2022-06-29 10:56:12 +03:00
qemu-config.c	util/qemu-config: Fix "query-command-line-options" to provide the right values	2022-12-15 15:19:23 +01:00
qemu-coroutine-io.c	Remove qemu-common.h include from most units	2022-04-06 14:31:55 +02:00
qemu-coroutine-lock.c	coroutine: Clean up superfluous inclusion of qemu/coroutine.h	2023-01-19 10:18:28 +01:00
qemu-coroutine-sleep.c	coroutine: Clean up superfluous inclusion of qemu/coroutine.h	2023-01-19 10:18:28 +01:00
qemu-coroutine.c	coroutine: Clean up superfluous inclusion of qemu/coroutine.h	2023-01-19 10:18:28 +01:00
qemu-option.c	qemu-option: Allow deleting opts during qemu_opts_foreach()	2021-10-15 16:11:22 +02:00
qemu-print.c
qemu-progress.c	include: move progress API to qemu-progress.h	2022-04-06 14:31:43 +02:00
qemu-sockets.c	sockets: Use ERRP_GUARD() where obviously appropriate	2022-12-14 16:19:35 +01:00
qemu-thread-common.h
qemu-thread-posix.c	util: Introduce qemu_thread_set_affinity() and qemu_thread_get_affinity()	2022-10-27 11:00:36 +02:00
qemu-thread-win32.c	util: Introduce qemu_thread_set_affinity() and qemu_thread_get_affinity()	2022-10-27 11:00:36 +02:00
qemu-timer-common.c
qemu-timer.c	qemu-timer: Skip empty timer lists before locking in qemu_clock_deadline_ns_all	2022-06-21 09:24:34 -07:00
qht.c	osdep: Move memalign-related functions to their own header	2022-03-07 13:16:49 +00:00
qsp.c
range.c
rcu.c	rcu: use coroutine TLS macros	2022-03-04 18:14:40 +01:00
readline.c
selfmap.c
stats64.c
sys_membarrier.c
systemd.c
thread-context.c	qapi: Use returned bool to check for failure (again)	2022-12-14 16:19:35 +01:00
thread-pool.c	thread-pool: remove stopping variable	2022-05-25 21:26:26 +02:00
throttle.c
timed-average.c
trace-events
trace.h
transactions.c	transactions: Invoke clean() after everything else	2021-11-16 09:43:44 +01:00
unicode.c
uri.c
userfaultfd.c
uuid.c
vfio-helpers.c	error handling: Use RETRY_ON_EINTR() macro where applicable	2023-01-09 13:50:47 +01:00
vhost-user-server.c	util: rename qemu_*block() socket functions	2022-05-03 15:53:20 +04:00
yank.c