* [Qemu-devel] [PATCH v4] glib: fix g_poll early timeout on windows
@ 2014-05-07 9:07 Stanislav Vorobiov
2014-05-07 12:21 ` Michael Tokarev
0 siblings, 1 reply; 4+ messages in thread
From: Stanislav Vorobiov @ 2014-05-07 9:07 UTC (permalink / raw)
To: qemu-devel; +Cc: alex, sw, sangho1206.park, stefanha, syeon.hwang, pbonzini
From: Sangho Park <sangho1206.park@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.vorobiov@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..1280fb2 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, timeout)
+gint g_poll_fixed(GPollFD *fds, guint nfds, gint timeout);
+#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..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;
+}
--
1.7.9.5
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH v4] glib: fix g_poll early timeout on windows
2014-05-07 9:07 [Qemu-devel] [PATCH v4] glib: fix g_poll early timeout on windows Stanislav Vorobiov
@ 2014-05-07 12:21 ` Michael Tokarev
2014-05-07 12:36 ` Stanislav Vorobiov
0 siblings, 1 reply; 4+ messages in thread
From: Michael Tokarev @ 2014-05-07 12:21 UTC (permalink / raw)
To: Stanislav Vorobiov, qemu-devel
Cc: alex, sw, sangho1206.park, stefanha, syeon.hwang, pbonzini
07.05.2014 13:07, Stanislav Vorobiov wrote:
> From: Sangho Park <sangho1206.park@samsung.com>
[]
> include/glib-compat.h | 19 +++++++++
> include/qemu-common.h | 12 ------
JFYI, this will clash with glib cleanup series I posted earlier
(http://thread.gmane.org/gmane.comp.emulators.qemu/270259)
with some of these patches being pushed via trivial tree
now (http://thread.gmane.org/gmane.comp.emulators.qemu/270767)
Thanks,
/mjt
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH v4] glib: fix g_poll early timeout on windows
2014-05-07 12:21 ` Michael Tokarev
@ 2014-05-07 12:36 ` Stanislav Vorobiov
2014-05-08 8:19 ` Michael Tokarev
0 siblings, 1 reply; 4+ messages in thread
From: Stanislav Vorobiov @ 2014-05-07 12:36 UTC (permalink / raw)
To: Michael Tokarev, qemu-devel
Cc: alex, sw, sangho1206.park, stefanha, syeon.hwang, pbonzini
Hi,
IMHO it's not a problem, automerge will resolve this
On 05/07/2014 04:21 PM, Michael Tokarev wrote:
> 07.05.2014 13:07, Stanislav Vorobiov wrote:
>> From: Sangho Park <sangho1206.park@samsung.com>
> []
>> include/glib-compat.h | 19 +++++++++
>> include/qemu-common.h | 12 ------
>
> JFYI, this will clash with glib cleanup series I posted earlier
> (http://thread.gmane.org/gmane.comp.emulators.qemu/270259)
> with some of these patches being pushed via trivial tree
> now (http://thread.gmane.org/gmane.comp.emulators.qemu/270767)
>
> Thanks,
>
> /mjt
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH v4] glib: fix g_poll early timeout on windows
2014-05-07 12:36 ` Stanislav Vorobiov
@ 2014-05-08 8:19 ` Michael Tokarev
0 siblings, 0 replies; 4+ messages in thread
From: Michael Tokarev @ 2014-05-08 8:19 UTC (permalink / raw)
To: Stanislav Vorobiov, qemu-devel
Cc: alex, sw, sangho1206.park, stefanha, syeon.hwang, pbonzini
07.05.2014 16:36, Stanislav Vorobiov wrote:
> Hi,
>
> IMHO it's not a problem, automerge will resolve this
Now the trivial queue pull request has been processed, some
of this patch is in the tree. I don't know what is this
magic "automerge" which you're talking about. The thing
is that your code is a bit different (for one, it wraps
g_poll() definition in glib-compat.h into #ifdef WIN32,
for another it adds g_poll_fixed()), and the patch
does not apply anymore.
I'd suggest you to rebase and resubmit. Hopefully it wont
clash with further glib-compat additions which are on the
way.
Thank you!
/mjt
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2014-05-08 8:19 UTC | newest]
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2014-05-07 9:07 [Qemu-devel] [PATCH v4] glib: fix g_poll early timeout on windows Stanislav Vorobiov
2014-05-07 12:21 ` Michael Tokarev
2014-05-07 12:36 ` Stanislav Vorobiov
2014-05-08 8:19 ` Michael Tokarev
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