On 06/14/2011 07:10 AM, Peter Zijlstra wrote:
On Mon, 2011-06-13 at 19:31 -0400, Glauber Costa wrote:
+static inline int 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;
+ this_rq()->prev_steal_time += steal;
If you move this addition below this test:
+ if (is_idle || (steal< TICK_NSEC))
+ return 0;
that is, right here, then you don't loose tiny steal deltas and
subsequent ticks accumulate their steal time until you really
have a full steal tick to account.
true
I guess you want something different for the idle case though.
definitely.
+ while (steal> TICK_NSEC) {
/* really, if we wanted a division we'd have written one */
asm("" : "+rm" (steal));
Out of curiosity, have we seen any compiler de-optimize it to a
division, or are you just being careful ?
+ steal -= TICK_NSEC;
+ st++;
+ }
+
+ account_steal_time(st);
+ return 1;
+ }
+ return 0;
+}
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