Hi, everyone
Any comments on this one ? This patch fixes
pretty serious performance issues on windows, it would be
great to have this in 2.0.0
On 04/15/2014 12:41 PM, Stanislav Vorobiov wrote:
> From: Sangho Park <sangho1206.p...@samsung.com>
>
> g_poll has a problem on windows when using
> timeouts < 10ms, in glib/gpoll.c:
>
> /* If not, and we have a significant timeout, poll again with
> * timeout then. Note that this will return indication for only
> * one event, or only for messages. We ignore timeouts less than
> * ten milliseconds as they are mostly pointless on Windows, the
> * MsgWaitForMultipleObjectsEx() call will timeout right away
> * anyway.
> */
> if (retval == 0 && (timeout == INFINITE || timeout >= 10))
> retval = poll_rest (poll_msgs, handles, nhandles, fds, nfds, timeout);
>
> so whenever g_poll is called with timeout < 10ms it does
> a quick poll instead of wait, this causes significant performance
> degradation of qemu, thus we should use WaitForMultipleObjectsEx
> directly
>
> Signed-off-by: Stanislav Vorobiov <s.vorob...@samsung.com>
> ---
> qemu-timer.c | 91
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 91 insertions(+)
>
> diff --git a/qemu-timer.c b/qemu-timer.c
> index e15ce47..9fb92cb 100644
> --- a/qemu-timer.c
> +++ b/qemu-timer.c
> @@ -315,6 +315,97 @@ int qemu_poll_ns(GPollFD *fds, guint nfds, int64_t
> timeout)
> ts.tv_nsec = timeout % 1000000000LL;
> return ppoll((struct pollfd *)fds, nfds, &ts, NULL);
> }
> +#elif defined(_WIN32)
> + guint i;
> + HANDLE handles[MAXIMUM_WAIT_OBJECTS];
> + gint nhandles = 0;
> + int num_completed = 0;
> + gint timeout_ms = qemu_timeout_ns_to_ms(timeout);
> +
> + for (i = 0; i < nfds; i++) {
> + gint j;
> +
> + if (fds[i].fd <= 0) {
> + continue;
> + }
> +
> + /* don't add same handle several times
> + */
> + for (j = 0; j < nhandles; j++) {
> + if (handles[j] == (HANDLE)fds[i].fd) {
> + break;
> + }
> + }
> +
> + if (j == nhandles) {
> + if (nhandles == MAXIMUM_WAIT_OBJECTS) {
> + fprintf(stderr, "Too many handles to wait for!\n");
> + break;
> + } else {
> + handles[nhandles++] = (HANDLE)fds[i].fd;
> + }
> + }
> + }
> +
> + for (i = 0; i < nfds; ++i) {
> + fds[i].revents = 0;
> + }
> +
> + if (timeout_ms == -1) {
> + timeout_ms = INFINITE;
> + }
> +
> + if (nhandles == 0) {
> + if (timeout_ms == INFINITE) {
> + return -1;
> + } else {
> + SleepEx(timeout_ms, TRUE);
> + return 0;
> + }
> + }
> +
> + while (1) {
> + DWORD res;
> + gint j;
> +
> + res = WaitForMultipleObjectsEx(nhandles, handles, FALSE,
> + timeout_ms, TRUE);
> +
> + if (res == WAIT_FAILED) {
> + for (i = 0; i < nfds; ++i) {
> + fds[i].revents = 0;
> + }
> +
> + return -1;
> + } else if ((res == WAIT_TIMEOUT) || (res == WAIT_IO_COMPLETION) ||
> + ((int)res < WAIT_OBJECT_0) ||
> + (res >= (WAIT_OBJECT_0 + nhandles))) {
> + break;
> + }
> +
> + for (i = 0; i < nfds; ++i) {
> + if (handles[res - WAIT_OBJECT_0] == (HANDLE)fds[i].fd) {
> + fds[i].revents = fds[i].events;
> + }
> + }
> +
> + ++num_completed;
> +
> + if (nhandles <= 1) {
> + break;
> + }
> +
> + /* poll the rest of the handles
> + */
> + for (j = res - WAIT_OBJECT_0 + 1; j < nhandles; j++) {
> + handles[j - 1] = handles[j];
> + }
> + --nhandles;
> +
> + timeout_ms = 0;
> + }
> +
> + return num_completed;
> #else
> return g_poll(fds, nfds, qemu_timeout_ns_to_ms(timeout));
> #endif
>
