On 06/17/2011 01:20 AM, Glauber Costa wrote:
This patch accounts steal time time in kernel/sched.
I kept it from last proposal, because I still see advantages
in it: Doing it here will give us easier access from scheduler
variables such as the cpu rq. The next patch shows an example of
usage for it.
Since functions like account_idle_time() can be called from
multiple places, not only account_process_tick(), steal time
grabbing is repeated in each account function separatedely.
/*
+ * We have to at flush steal time information every time something else
+ * is accounted. Since the accounting functions are all visible to the rest
+ * of the kernel, it gets tricky to do them in one place. This helper function
+ * helps us.
+ *
+ * When the system is idle, the concept of steal time does not apply. We just
+ * tell the underlying hypervisor that we grabbed the data, but skip steal time
+ * accounting
+ */
+static inline bool touch_steal_time(int is_idle)
+{
+ u64 steal, st = 0;
+
+ if (static_branch(¶virt_steal_enabled)) {
+
+ steal = paravirt_steal_clock(smp_processor_id());
+
+ steal -= this_rq()->prev_steal_time;
+ if (is_idle) {
+ this_rq()->prev_steal_time += steal;
+ return false;
+ }
+
+ while (steal>= TICK_NSEC) {
+ /*
+ * Inline assembly required to prevent the compiler
+ * optimising this loop into a divmod call.
+ * See __iter_div_u64_rem() for another example of this.
+ */
Why not use said function?
+ asm("" : "+rm" (steal));
+
+ steal -= TICK_NSEC;
+ this_rq()->prev_steal_time += TICK_NSEC;
+ st++;
Suppose a live migration or SIGSTOP causes lots of steal time. How long
will we spend here?
+ }
+
+ account_steal_time(st);
+ return !!st;
!! !needed, you're returning a bool.
+ }
+ return false;
+}
+
I'll need Peter's (or another sched maintainer's) review to apply this.
--
error compiling committee.c: too many arguments to function
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