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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html