Messages in this thread Patch in this message | | | Date | Thu, 16 Apr 2020 12:47:25 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v3 6/9] sched: Kill select_task_rq()'s sd_flag parameter |
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On Thu, Apr 16, 2020 at 09:42:36AM +0200, Vincent Guittot wrote: > On Wed, 15 Apr 2020 at 23:05, Valentin Schneider > > @@ -6622,13 +6622,25 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) > > * preempt must be disabled. > > */ > > static int > > +select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) > > { > > + int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING); > > struct sched_domain *tmp, *sd = NULL; > > int cpu = smp_processor_id(); > > int new_cpu = prev_cpu; > > int want_affine = 0; > > - int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING); > > + int sd_flag; > > + > > + switch (wake_flags & (WF_TTWU | WF_FORK | WF_EXEC)) { > > You remove a function parameter, which was directly set with the right > flag, but then you add a switch case to recreate this sd_flag > internally. Not sure we can say that it's real benefit > > > + case WF_TTWU: > > + sd_flag = SD_BALANCE_WAKE; > > + break; > > + case WF_FORK: > > + sd_flag = SD_BALANCE_FORK; > > + break; > > + default: > > + sd_flag = SD_BALANCE_EXEC; > > + }
Agreed, that's a bit yuck, how about something like so instead:
--- a/include/linux/sched/topology.h +++ b/include/linux/sched/topology.h @@ -11,10 +11,12 @@ */ #ifdef CONFIG_SMP +/* First nibble of SD_flag is shared with WF_flag */ #define SD_BALANCE_NEWIDLE 0x0001 /* Balance when about to become idle */ #define SD_BALANCE_EXEC 0x0002 /* Balance on exec */ #define SD_BALANCE_FORK 0x0004 /* Balance on fork, clone */ #define SD_BALANCE_WAKE 0x0008 /* Balance on wakeup */ + #define SD_WAKE_AFFINE 0x0010 /* Wake task to waking CPU */ #define SD_ASYM_CPUCAPACITY 0x0020 /* Domain members have different CPU capacities */ #define SD_SHARE_CPUCAPACITY 0x0040 /* Domain members share CPU capacity */ --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6635,16 +6635,8 @@ select_task_rq_fair(struct task_struct * int want_affine = 0; int sd_flag; - switch (wake_flags & (WF_TTWU | WF_FORK | WF_EXEC)) { - case WF_TTWU: - sd_flag = SD_BALANCE_WAKE; - break; - case WF_FORK: - sd_flag = SD_BALANCE_FORK; - break; - default: - sd_flag = SD_BALANCE_EXEC; - } + /* SD_flags and WF_flags share the first nibble */ + sd_flag = wake_flags & 0xf; if (sd_flag & SD_BALANCE_WAKE) { record_wakee(p); --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1685,11 +1685,12 @@ static inline int task_on_rq_migrating(s /* * Wake flags */ -#define WF_SYNC 0x01 /* Waker goes to sleep after wakeup */ -#define WF_TTWU 0x02 /* Regular task wakeup */ -#define WF_FORK 0x04 /* Child wakeup after fork */ -#define WF_EXEC 0x08 /* "Fake" wakeup at exec */ -#define WF_MIGRATED 0x10 /* Internal use, task got migrated */ +#define WF_EXEC 0x02 /* SD_BALANCE_EXEC */ +#define WF_FORK 0x04 /* SD_BALANCE_FORK */ +#define WF_TTWU 0x08 /* SD_BALANCE_WAKE */ + +#define WF_SYNC 0x10 /* Waker goes to sleep after wakeup */ +#define WF_MIGRATED 0x20 /* Internal use, task got migrated */ /* * To aid in avoiding the subversion of "niceness" due to uneven distribution
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