Messages in this thread Patch in this message | | | Date | Wed, 31 Oct 2018 19:45:27 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/fair: util_est: fix cpu_util_wake for execl |
| |
On Tue, Oct 30, 2018 at 04:09:47PM +0000, Patrick Bellasi wrote:
> Let's fix this by ensuring to always discount the task estimated > utilization from the CPU's estimated utilization when the task is also > the current one. The same benchmark of the bug report, executed on a > dual socket 40 CPUs Intel(R) Xeon(R) CPU E5-2690 v2 @ 3.00GHz machine, > reports these "Execl Throughput" figures (higher the better):
Before this we have:
/* Discount task's blocked util from CPU's util */ util -= min_t(unsigned int, util, task_util(p));
at the very least that comment is now inaccurate, since @p might not be blocked.
> @@ -6258,8 +6267,17 @@ static unsigned long cpu_util_wake(int cpu, struct task_struct *p) > * covered by the following code when estimated utilization is > * enabled. > */ > - if (sched_feat(UTIL_EST)) > - util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued)); > + if (sched_feat(UTIL_EST)) { > + unsigned int estimated = > + READ_ONCE(cfs_rq->avg.util_est.enqueued); > + > + if (unlikely(current == p || task_on_rq_queued(p))) {
I'm confused by the need for 'current == p', afaict task_on_rq_queued(p) is sufficient -- we've already established task_cpu(p) == cpu earlier.
> + estimated -= min_t(unsigned int, estimated, > + (_task_util_est(p) | UTIL_AVG_UNCHANGED)); > + } > + > + util = max(util, estimated); > + }
Also, I think it is about time we find a suitable name for:
#define xxx(_var, _val) do { \ typeof(_var) var = (_var); \ typeof(_var) val = (_val); \ typeof(_var) res = var - val; \ if (res > var) \ res = 0; \ (_var) = res; \ } while (0)
Which is basically sub_positive() but without the READ_ONCE/WRITE_ONCE stuff. We do that:
var -= min_t(typeof(var), var, val);
pattern _all_ over.
| |