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reduce wakeups from smart scheduler

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The smart scheduler itimer currently always fires after each request
(which in turn causes the CPU to wake out of idle, burning precious
power). Rather than doing this, just stop the timer before going into
the select() portion of the WaitFor loop. It's a cheap system call, and
it will only get called if there's no more commands batched up from the
active fd.

This change also allows some of the functions to be simplified;
setitimer() will only fail if it's passed invalid data, and we don't do
that... so make it void and remove all the conditional code that deals
with failure.

The change also allows us to remove a few variables that were used for
housekeeping between the signal handler and the main loop.

Signed-off-by: Keith Packard <keithp@koto.keithp.com>
This commit is contained in:
Arjan van de Ven 2007-10-28 09:37:52 +01:00 committed by Keith Packard
parent 692654b430
commit 2338d5c991
3 changed files with 8 additions and 37 deletions
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6
include/dixstruct.h
View File

@ -150,11 +150,9 @@ extern long SmartScheduleTime;
extern long SmartScheduleInterval;
extern long SmartScheduleSlice;
extern long SmartScheduleMaxSlice;
extern unsigned long SmartScheduleIdleCount;
extern Bool SmartScheduleDisable;
extern Bool SmartScheduleIdle;
extern Bool SmartScheduleTimerStopped;
extern Bool SmartScheduleStartTimer(void);
extern void SmartScheduleStartTimer(void);
extern void SmartScheduleStopTimer(void);
#define SMART_MAX_PRIORITY (20)
#define SMART_MIN_PRIORITY (-20)

11
os/WaitFor.c
View File

@ -217,7 +217,8 @@ WaitForSomething(int *pClientsReady)
XFD_COPYSET(&AllSockets, &LastSelectMask);
#ifdef SMART_SCHEDULE
}
SmartScheduleIdle = TRUE;
SmartScheduleStopTimer ();
#endif
BlockHandler((pointer)&wt, (pointer)&LastSelectMask);
if (NewOutputPending)
@ -237,13 +238,7 @@ WaitForSomething(int *pClientsReady)
selecterr = GetErrno();
WakeupHandler(i, (pointer)&LastSelectMask);
#ifdef SMART_SCHEDULE
if (i >= 0)
{
SmartScheduleIdle = FALSE;
SmartScheduleIdleCount = 0;
if (SmartScheduleTimerStopped)
(void) SmartScheduleStartTimer ();
}
SmartScheduleStartTimer ();
#endif
if (i <= 0) /* An error or timeout occurred */
{

28
os/utils.c
View File

@ -1513,10 +1513,6 @@ XNFstrdup(const char *s)
#ifdef SMART_SCHEDULE
unsigned long SmartScheduleIdleCount;
Bool SmartScheduleIdle;
Bool SmartScheduleTimerStopped;
#ifdef SIGVTALRM
#define SMART_SCHEDULE_POSSIBLE
#endif
@ -1526,7 +1522,7 @@ Bool SmartScheduleTimerStopped;
#define SMART_SCHEDULE_TIMER ITIMER_REAL
#endif
static void
void
SmartScheduleStopTimer (void)
{
#ifdef SMART_SCHEDULE_POSSIBLE
@ -1537,38 +1533,28 @@ SmartScheduleStopTimer (void)
timer.it_value.tv_sec = 0;
timer.it_value.tv_usec = 0;
(void) setitimer (ITIMER_REAL, &timer, 0);
SmartScheduleTimerStopped = TRUE;
#endif
}
Bool
void
SmartScheduleStartTimer (void)
{
#ifdef SMART_SCHEDULE_POSSIBLE
struct itimerval timer;
SmartScheduleTimerStopped = FALSE;
timer.it_interval.tv_sec = 0;
timer.it_interval.tv_usec = SmartScheduleInterval * 1000;
timer.it_value.tv_sec = 0;
timer.it_value.tv_usec = SmartScheduleInterval * 1000;
return setitimer (ITIMER_REAL, &timer, 0) >= 0;
setitimer (ITIMER_REAL, &timer, 0);
#endif
return FALSE;
}
#ifdef SMART_SCHEDULE_POSSIBLE
static void
SmartScheduleTimer (int sig)
{
int olderrno = errno;
SmartScheduleTime += SmartScheduleInterval;
if (SmartScheduleIdle)
{
SmartScheduleStopTimer ();
}
errno = olderrno;
}
#endif
@ -1592,14 +1578,6 @@ SmartScheduleInit (void)
perror ("sigaction for smart scheduler");
return FALSE;
}
/* Set up the virtual timer */
if (!SmartScheduleStartTimer ())
{
perror ("scheduling timer");
return FALSE;
}
/* stop the timer and wait for WaitForSomething to start it */
SmartScheduleStopTimer ();
return TRUE;
#else
return FALSE;