From 5a007547df76446ab891df93ebc55749716609bf Mon Sep 17 00:00:00 2001 From: Sangho Park Date: Thu, 8 May 2014 12:47:10 +0400 Subject: glib: fix g_poll early timeout on windows 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 Signed-off-by: Stefan Hajnoczi --- util/oslib-win32.c | 112 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 112 insertions(+) (limited to 'util/oslib-win32.c') diff --git a/util/oslib-win32.c b/util/oslib-win32.c index 93f7d35..69552f7 100644 --- a/util/oslib-win32.c +++ b/util/oslib-win32.c @@ -238,3 +238,115 @@ char *qemu_get_exec_dir(void) { return g_strdup(exec_dir); } + +/* + * 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 + */ +gint g_poll_fixed(GPollFD *fds, guint nfds, gint timeout) +{ + guint i; + HANDLE handles[MAXIMUM_WAIT_OBJECTS]; + gint nhandles = 0; + int num_completed = 0; + + 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 == -1) { + timeout = INFINITE; + } + + if (nhandles == 0) { + if (timeout == INFINITE) { + return -1; + } else { + SleepEx(timeout, TRUE); + return 0; + } + } + + while (1) { + DWORD res; + gint j; + + res = WaitForMultipleObjectsEx(nhandles, handles, FALSE, + timeout, 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 < (int)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 = 0; + } + + return num_completed; +} -- cgit v1.1