Please see my remarks below.
Am 18.04.2014 13:51, schrieb Stanislav Vorobiov:
> 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>
> ---
> include/glib-compat.h | 19 +++++++++
> include/qemu-common.h | 12 ------
> util/oslib-win32.c | 112
> +++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 131 insertions(+), 12 deletions(-)
>
> diff --git a/include/glib-compat.h b/include/glib-compat.h
> index 8aa77af..2d4258e 100644
> --- a/include/glib-compat.h
> +++ b/include/glib-compat.h
> @@ -24,4 +24,23 @@ static inline guint g_timeout_add_seconds(guint interval,
> GSourceFunc function,
> }
> #endif
>
> +#ifdef _WIN32
> +/*
> + * g_poll has a problem on windows when using
> + * timeouts < 10ms, so use wrapper.
> + */
> +#define g_poll(fds, nfds, timeout) g_poll_fixed(fds, nfds,
> qemu_timeout_ns_to_ms(timeout))
qemu_timeout_ns_to_ms is not needed here (g_poll is called with timeout
given in ms, and so is g_poll_fixed).
> +gint g_poll_fixed(GPollFD *fds, guint nfds, gint timeout_ms);
> +#elif !GLIB_CHECK_VERSION(2, 20, 0)
> +/*
> + * Glib before 2.20.0 doesn't implement g_poll, so wrap it to compile
> properly
> + * on older systems.
> + */
> +static inline gint g_poll(GPollFD *fds, guint nfds, gint timeout)
> +{
> + GMainContext *ctx = g_main_context_default();
> + return g_main_context_get_poll_func(ctx)(fds, nfds, timeout);
> +}
> +#endif
> +
> #endif
> diff --git a/include/qemu-common.h b/include/qemu-common.h
> index a998e8d..3f3fd60 100644
> --- a/include/qemu-common.h
> +++ b/include/qemu-common.h
> @@ -124,18 +124,6 @@ int qemu_main(int argc, char **argv, char **envp);
> void qemu_get_timedate(struct tm *tm, int offset);
> int qemu_timedate_diff(struct tm *tm);
>
> -#if !GLIB_CHECK_VERSION(2, 20, 0)
> -/*
> - * Glib before 2.20.0 doesn't implement g_poll, so wrap it to compile
> properly
> - * on older systems.
> - */
> -static inline gint g_poll(GPollFD *fds, guint nfds, gint timeout)
> -{
> - GMainContext *ctx = g_main_context_default();
> - return g_main_context_get_poll_func(ctx)(fds, nfds, timeout);
> -}
> -#endif
> -
> /**
> * is_help_option:
> * @s: string to test
> diff --git a/util/oslib-win32.c b/util/oslib-win32.c
> index 93f7d35..006259e 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
Windows
> + * 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
QEMU
> + * directly
> + */
> +gint g_poll_fixed(GPollFD *fds, guint nfds, gint timeout_ms)
> +{
> + 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_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;
> +}
>
Please send patches as top level e-mails (no In-Reply-To) and cc at
least one maintainer (otherwise you risk that your patch is not noticed).
Thanks,
Stefan
