Ticket #4677 (new defect)
Sugar apps' pygtk main loop polls 10 times a second, always; rest of Sugar polls too
| Reported by: | gnu | Owned by: | marco |
|---|---|---|---|
| Priority: | high | Milestone: | 9.1.0-cancelled |
| Component: | sugar | Version: | 1.0-software-build-623 |
| Keywords: | power 9.1.0? needs-testing | Cc: | |
| Action Needed: | code | Verified: | no |
| Deployments affected: | Blocked By: | ||
| Blocking: |
Description
I noticed that the simcity Python helper process was doing tons of system calls -- lots of poll() calls with timeouts of 100ms. You can see this by running the strace command on any Python sugar application, such as the Journal's sugar-activity-factory,
The sugar_shell_service polls every 1 second (1000 ms); I don't know by what mechanism.
The sugar_datastore_service sets this timeout to 0 (it polls constantly), but it then uses select() to delay for 2.5ms. So it polls about 400 times a second.
So I debugged the SimCity one. The timeout is used in the poll() call in g_main_loop_run() in glib2, and is set by this code in pygtk_main_watch_prepare in pygtk2's gtk.override:
1058 /* This code (pygtk main watch) was copied with minor changes from 1059 * pygobject/gobject/pygmainloop.c */ 1060 static gboolean 1061 pygtk_main_watch_prepare(GSource *source, 1062 int *timeout) 1063 { 1064 /* Python only invokes signal handlers from the main thread, 1065 * so if a thread other than the main thread receives the signal 1066 * from the kernel, PyErr_CheckSignals() from that thread will 1067 * do nothing. So, we need to time out and check for signals 1068 * regularily too. 1069 * Also, on Windows g_poll() won't be interrupted by a signal 1070 * (AFAIK), so we need the timeout there too. 1071 */ 1072 #ifndef PLATFORM_WIN32 1073 if (pyg_threads_enabled) 1074 #endif 1075 *timeout = 100;
Clearly, this code should not be waking up every 10th of a second to "check for signals" -- neither on the OLPC, nor on millions of other machines running Python GTK applications. But I don't know enough about this code to suggest a fix.
