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qemu/util
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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 util: Add CRC16 (CCITT) calculation routines 2021-01-24 20:10:54 +01:00
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 utils/fifo8: change fatal errors from abort() to assert() 2021-02-07 20:38:20 +00:00
filemonitor-inotify.c
filemonitor-stub.c
getauxval.c
guest-random.c util/guest-random: Fix size arg to tail memcpy 2021-07-09 18:42:46 +02:00
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 net: Use id_generate() in the network subsystem, too 2021-03-09 21:47:45 +01:00
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 co-shared-resource: protect with a mutex 2021-06-25 14:24:24 +03:00
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 semihosting: Implement SYS_ELAPSED and SYS_TICKFREQ 2021-01-18 10:05:06 +00:00
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 qemu/atomic: Add aligned_{int64,uint64}_t types 2021-07-21 07:45:38 -10:00
range.c
rcu.c rcu: use coroutine TLS macros 2022-03-04 18:14:40 +01:00
readline.c readline: Fix possible array index out of bounds in readline_hist_add() 2021-01-04 11:13:39 +00:00
selfmap.c util/selfmap: Discard mapping on error 2021-07-26 07:06:49 -10:00
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 Remove superfluous timer_del() calls 2021-01-08 15:13:38 +00:00
timed-average.c
trace-events modules: add tracepoints 2021-07-09 18:20:27 +02:00
trace.h
transactions.c transactions: Invoke clean() after everything else 2021-11-16 09:43:44 +01:00
unicode.c
uri.c util/uri: do not check argument of uri_free() 2021-07-09 12:26:05 +02:00
userfaultfd.c migration: introduce UFFD-WP low-level interface helpers 2021-02-08 11:19:51 +00:00
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 yank: Remove dependency on qiochannel 2021-04-01 15:27:44 +04:00