qemu-e2k/util
Stefan Hajnoczi 826cc32423 aio-posix: split poll check from ready handler
Adaptive polling measures the execution time of the polling check plus
handlers called when a polled event becomes ready. Handlers can take a
significant amount of time, making it look like polling was running for
a long time when in fact the event handler was running for a long time.

For example, on Linux the io_submit(2) syscall invoked when a virtio-blk
device's virtqueue becomes ready can take 10s of microseconds. This
can exceed the default polling interval (32 microseconds) and cause
adaptive polling to stop polling.

By excluding the handler's execution time from the polling check we make
the adaptive polling calculation more accurate. As a result, the event
loop now stays in polling mode where previously it would have fallen
back to file descriptor monitoring.

The following data was collected with virtio-blk num-queues=2
event_idx=off using an IOThread. Before:

168k IOPS, IOThread syscalls:

  9837.115 ( 0.020 ms): IO iothread1/620155 io_submit(ctx_id: 140512552468480, nr: 16, iocbpp: 0x7fcb9f937db0)    = 16
  9837.158 ( 0.002 ms): IO iothread1/620155 write(fd: 103, buf: 0x556a2ef71b88, count: 8)                         = 8
  9837.161 ( 0.001 ms): IO iothread1/620155 write(fd: 104, buf: 0x556a2ef71b88, count: 8)                         = 8
  9837.163 ( 0.001 ms): IO iothread1/620155 ppoll(ufds: 0x7fcb90002800, nfds: 4, tsp: 0x7fcb9f1342d0, sigsetsize: 8) = 3
  9837.164 ( 0.001 ms): IO iothread1/620155 read(fd: 107, buf: 0x7fcb9f939cc0, count: 512)                        = 8
  9837.174 ( 0.001 ms): IO iothread1/620155 read(fd: 105, buf: 0x7fcb9f939cc0, count: 512)                        = 8
  9837.176 ( 0.001 ms): IO iothread1/620155 read(fd: 106, buf: 0x7fcb9f939cc0, count: 512)                        = 8
  9837.209 ( 0.035 ms): IO iothread1/620155 io_submit(ctx_id: 140512552468480, nr: 32, iocbpp: 0x7fca7d0cebe0)    = 32

174k IOPS (+3.6%), IOThread syscalls:

  9809.566 ( 0.036 ms): IO iothread1/623061 io_submit(ctx_id: 140539805028352, nr: 32, iocbpp: 0x7fd0cdd62be0)    = 32
  9809.625 ( 0.001 ms): IO iothread1/623061 write(fd: 103, buf: 0x5647cfba5f58, count: 8)                         = 8
  9809.627 ( 0.002 ms): IO iothread1/623061 write(fd: 104, buf: 0x5647cfba5f58, count: 8)                         = 8
  9809.663 ( 0.036 ms): IO iothread1/623061 io_submit(ctx_id: 140539805028352, nr: 32, iocbpp: 0x7fd0d0388b50)    = 32

Notice that ppoll(2) and eventfd read(2) syscalls are eliminated because
the IOThread stays in polling mode instead of falling back to file
descriptor monitoring.

As usual, polling is not implemented on Windows so this patch ignores
the new io_poll_read() callback in aio-win32.c.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20211207132336.36627-2-stefanha@redhat.com

[Fixed up aio_set_event_notifier() calls in
tests/unit/test-fdmon-epoll.c added after this series was queued.
--Stefan]

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2022-01-12 17:09:39 +00:00
..
aio-posix.c aio-posix: split poll check from ready handler 2022-01-12 17:09:39 +00:00
aio-posix.h aio-posix: split poll check from ready handler 2022-01-12 17:09:39 +00:00
aio-wait.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
aio-win32.c aio-posix: split poll check from ready handler 2022-01-12 17:09:39 +00:00
aiocb.c
async.c aio-posix: split poll check from ready handler 2022-01-12 17:09:39 +00:00
atomic64.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
base64.c nomaintainer: Fix Lesser GPL version number 2020-11-15 17:04:40 +01:00
bitmap.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
bitops.c
block-helpers.c block: move logical block size check function to a common utility function 2020-10-23 13:42:16 +01:00
block-helpers.h block: move logical block size check function to a common utility function 2020-10-23 13:42:16 +01:00
buffer.c nomaintainer: Fix Lesser GPL version number 2020-11-15 17:04:40 +01:00
bufferiszero.c
cacheflush.c util/cacheflush: Fix error generated by clang 2021-01-21 13:00:41 +01:00
cacheinfo.c util: Enhance flush_icache_range with separate data pointer 2021-01-07 05:09:41 -10:00
compatfd.c util/compatfd.c: use libc signalfd wrapper instead of raw syscall 2021-10-13 10:47:49 +02:00
coroutine-sigaltstack.c coroutine-sigaltstack: Add SIGUSR2 mutex 2021-01-26 14:36:37 +01:00
coroutine-ucontext.c Remove the CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE switch 2020-07-13 11:40:52 +02:00
coroutine-win32.c
crc32c.c
crc-ccitt.c util: Add CRC16 (CCITT) calculation routines 2021-01-24 20:10:54 +01:00
cutils.c cutils: fix memory leak in get_relocated_path() 2021-05-13 18:06:40 +02:00
dbus.c
drm.c util/drm: make portable by avoiding struct dirent d_type 2020-07-13 14:36:10 +01:00
envlist.c
error.c
event_notifier-posix.c event_notifier: Set ->initialized earlier in event_notifier_init() 2021-02-16 17:15:39 +01:00
event_notifier-win32.c
fdmon-epoll.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
fdmon-io_uring.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
fdmon-poll.c fdmon-poll: reset npfd when upgrading to fdmon-epoll 2020-09-23 13:45:52 +01:00
fifo8.c utils/fifo8: change fatal errors from abort() to assert() 2021-02-07 20:38:20 +00:00
filemonitor-inotify.c nomaintainer: Fix Lesser GPL version number 2020-11-15 17:04:40 +01:00
filemonitor-stub.c nomaintainer: Fix Lesser GPL version number 2020-11-15 17:04:40 +01:00
getauxval.c util/getauxval: Porting to FreeBSD getauxval feature 2020-06-26 06:45:29 -04:00
guest-random.c util/guest-random: Fix size arg to tail memcpy 2021-07-09 18:42:46 +02:00
hbitmap.c
hexdump.c util/hexdump: introduce qemu_hexdump_line() 2020-09-29 02:14:30 -04:00
host-utils.c host-utils: add 128-bit quotient support to divu128/divs128 2021-10-27 17:10:00 -07:00
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
iov.c util/iov: make qemu_iovec_init_extended() honest 2021-02-03 08:00:33 -06:00
iova-tree.c util: Make some iova_tree parameters const 2021-11-02 15:57:21 +01:00
keyval.c keyval: introduce keyval_parse_into 2021-07-06 08:33:51 +02:00
lockcnt.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
log.c nomaintainer: Fix Lesser GPL version number 2020-11-15 17:04:40 +01:00
main-loop.c aio-posix: split poll check from ready handler 2022-01-12 17:09:39 +00:00
memfd.c
meson.build qemu/int128: addition of div/rem 128-bit operations 2022-01-08 15:46:10 +10:00
mmap-alloc.c Deprecate pmem=on with non-DAX capable backend file 2021-07-06 18:05:16 -04:00
module.c modules: check arch on qom lookup 2021-07-09 18:20:27 +02:00
notify.c
nvdimm-utils.c Clean up includes 2020-12-10 17:16:44 +01:00
osdep.c util/osdep: Add qemu_mprotect_rw 2021-06-13 17:42:40 -07:00
oslib-posix.c util/oslib-posix: Forward SIGBUS to MCE handler under Linux 2022-01-07 19:30:13 -05:00
oslib-win32.c util/oslib-win32: Fix fatal assertion in qemu_try_memalign 2021-06-19 14:51:51 -07:00
pagesize.c
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-config.c qemu-config: restore "machine" in qmp_query_command_line_options() 2021-07-22 14:44:47 +02:00
qemu-coroutine-io.c aio-posix: split poll check from ready handler 2022-01-12 17:09:39 +00:00
qemu-coroutine-lock.c coroutine-lock: Reimplement CoRwlock to fix downgrade bug 2021-03-31 10:44:21 +01:00
qemu-coroutine-sleep.c coroutine-sleep: introduce qemu_co_sleep 2021-05-21 18:22:33 +01:00
qemu-coroutine.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
qemu-error.c error: rename error_with_timestamp to message_with_timestamp 2021-02-01 10:50:55 +00:00
qemu-openpty.c util: Remove redundant checks in the openpty() 2021-09-15 14:42:48 +02:00
qemu-option.c qemu-option: Allow deleting opts during qemu_opts_foreach() 2021-10-15 16:11:22 +02:00
qemu-print.c monitor: Use getter/setter functions for cur_mon 2020-10-09 07:08:19 +02:00
qemu-progress.c util/: fix some comment spelling errors 2020-09-17 20:38:42 +02:00
qemu-sockets.c build-sys: add HAVE_IPPROTO_MPTCP 2021-09-30 15:30:25 +02:00
qemu-thread-common.h
qemu-thread-posix.c configure, meson: move pthread_setname_np checks to Meson 2021-10-14 09:50:57 +02:00
qemu-thread-win32.c util: Pass file+line to qemu_rec_mutex_unlock_impl 2021-06-16 15:03:26 +02:00
qemu-timer-common.c semihosting: Implement SYS_ELAPSED and SYS_TICKFREQ 2021-01-18 10:05:06 +00:00
qemu-timer.c spapr: rollback 'unplug timeout' for CPU hotunplugs 2021-04-12 12:27:14 +10:00
qht.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
qsp.c qemu/atomic: Add aligned_{int64,uint64}_t types 2021-07-21 07:45:38 -10:00
range.c
rcu.c rcu: Introduce force_rcu notifier 2021-11-10 13:20:15 +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 qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
sys_membarrier.c
systemd.c
thread-pool.c
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 trace: switch position of headers to what Meson requires 2020-08-21 06:18:24 -04:00
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 util/vfio-helpers: Let qemu_vfio_do_mapping() propagate Error 2021-09-07 09:08:24 +01:00
vhost-user-server.c aio-posix: split poll check from ready handler 2022-01-12 17:09:39 +00:00
yank.c yank: Remove dependency on qiochannel 2021-04-01 15:27:44 +04:00