On 27/03/16(Sun) 12:00, Martin Pieuchot wrote:
> Diff below moves resetpriority() out of updatepri() and resched_proc()
> out of resetpriority() in order to expose a double resched_proc() call
> in setrunnable().
>
> This happens when a thread has slept for more than 1 second. Since
> p_usrpri is equal or bigger than p_priority, if the first call
> triggers a need_resched() then the second will also do so.
>
> I'd like to commit this diff which does not introduce any behavior
> change then remove the first resched_proc() in setrunnable().
I'm still looking for oks for this diff.
I'm currently trying to have a better view of the differences in
voluntary vs involuntary context switches between SP and MP kernels
for the same workload. So removing a resched_proc() will help.
> Index: kern/sched_bsd.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/sched_bsd.c,v
> retrieving revision 1.43
> diff -u -p -r1.43 sched_bsd.c
> --- kern/sched_bsd.c 9 Mar 2016 13:38:50 -0000 1.43
> +++ kern/sched_bsd.c 24 Mar 2016 11:37:34 -0000
> @@ -246,6 +246,7 @@ schedcpu(void *arg)
> newcpu = (u_int) decay_cpu(loadfac, p->p_estcpu);
> p->p_estcpu = newcpu;
> resetpriority(p);
> + resched_proc(p, p->p_usrpri);
> if (p->p_priority >= PUSER) {
> if (p->p_stat == SRUN &&
> (p->p_priority / SCHED_PPQ) !=
> @@ -284,7 +285,6 @@ updatepri(struct proc *p)
> newcpu = (int) decay_cpu(loadfac, newcpu);
> p->p_estcpu = newcpu;
> }
> - resetpriority(p);
> }
>
> /*
> @@ -454,7 +454,7 @@ mi_switch(void)
> #endif
> }
>
> -static __inline void
> +void
> resched_proc(struct proc *p, u_char pri)
> {
> struct cpu_info *ci;
> @@ -509,8 +509,11 @@ setrunnable(struct proc *p)
> p->p_stat = SRUN;
> p->p_cpu = sched_choosecpu(p);
> setrunqueue(p);
> - if (p->p_slptime > 1)
> + if (p->p_slptime > 1) {
> updatepri(p);
> + resetpriority(p);
> + resched_proc(p, p->p_usrpri);
> + }
> p->p_slptime = 0;
> resched_proc(p, p->p_priority);
> }
> @@ -531,7 +534,6 @@ resetpriority(struct proc *p)
> NICE_WEIGHT * (p->p_p->ps_nice - NZERO);
> newpriority = min(newpriority, MAXPRI);
> p->p_usrpri = newpriority;
> - resched_proc(p, p->p_usrpri);
> }
>
> /*
> @@ -556,6 +558,7 @@ schedclock(struct proc *p)
> SCHED_LOCK(s);
> p->p_estcpu = ESTCPULIM(p->p_estcpu + 1);
> resetpriority(p);
> + resched_proc(p, p->p_usrpri);
> if (p->p_priority >= PUSER)
> p->p_priority = p->p_usrpri;
> SCHED_UNLOCK(s);
> Index: kern/kern_resource.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/kern_resource.c,v
> retrieving revision 1.55
> diff -u -p -r1.55 kern_resource.c
> --- kern/kern_resource.c 5 Dec 2015 10:11:53 -0000 1.55
> +++ kern/kern_resource.c 24 Mar 2016 11:30:32 -0000
> @@ -194,8 +194,10 @@ donice(struct proc *curp, struct process
> return (EACCES);
> chgpr->ps_nice = n;
> SCHED_LOCK(s);
> - TAILQ_FOREACH(p, &chgpr->ps_threads, p_thr_link)
> - (void)resetpriority(p);
> + TAILQ_FOREACH(p, &chgpr->ps_threads, p_thr_link) {
> + resetpriority(p);
> + resched_proc(p, p->p_usrpri);
> + }
> SCHED_UNLOCK(s);
> return (0);
> }
> Index: sys/sched.h
> ===================================================================
> RCS file: /cvs/src/sys/sys/sched.h,v
> retrieving revision 1.41
> diff -u -p -r1.41 sched.h
> --- sys/sched.h 17 Mar 2016 13:18:47 -0000 1.41
> +++ sys/sched.h 24 Mar 2016 11:35:38 -0000
> @@ -166,6 +166,7 @@ void sched_stop_secondary_cpus(void);
> #define cpu_is_idle(ci) ((ci)->ci_schedstate.spc_whichqs == 0)
>
> void sched_init_runqueues(void);
> +void resched_proc(struct proc *p, u_char);
> void setrunqueue(struct proc *);
> void remrunqueue(struct proc *);
>
>
