Messages in this thread | | | From | Valentin Schneider <> | Subject | Re: [PATCH v3 9/9] sched/topology: Define and use shortcut pointers for wakeup sd_flag scan | Date | Thu, 16 Apr 2020 11:24:20 +0100 |
| |
On 16/04/20 08:46, Vincent Guittot wrote: >> @@ -6657,7 +6646,19 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) >> >> rcu_read_lock(); >> >> - sd = highest_flag_domain(cpu, sd_flag); >> + switch (wake_flags & (WF_TTWU | WF_FORK | WF_EXEC)) { >> + case WF_TTWU: >> + sd_flag = SD_BALANCE_WAKE; >> + sd = rcu_dereference(per_cpu(sd_balance_wake, cpu)); > > It's worth having a direct pointer for the fast path which we always > try to keep short but the other paths are already slow and will not > get any benefit of this per cpu pointer. > We should keep the loop for the slow paths >
Which fast/slow paths are you referring to here? want_affine vs !want_affine? If so, do you then mean that we should do the switch case only when !want_affine, and otherwise look for the domain via the for_each_domain() loop?
>> + break; >> + case WF_FORK: >> + sd_flag = SD_BALANCE_FORK; >> + sd = rcu_dereference(per_cpu(sd_balance_fork, cpu)); >> + break; >> + default: >> + sd_flag = SD_BALANCE_EXEC; >> + sd = rcu_dereference(per_cpu(sd_balance_exec, cpu)); >> + } >> >> /* >> * If !want_affine, we just look for the highest domain where
| |