Re: [RFC PATCH v2 11/17] sched: Basic tracking of matching tasks

[Tim Chen]

On 4/23/19 9:18 AM, Vineeth Remanan Pillai wrote:

> +/* real prio, less is less */
> +static inline bool __prio_less(struct task_struct *a, struct task_struct *b, 
> bool core_cmp)
> +{
> +     u64 vruntime;
> +
> +     int pa = __task_prio(a), pb = __task_prio(b);
> +
> +     if (-pa < -pb)
> +             return true;
> +
> +     if (-pb < -pa)
> +             return false;
> +
> +     if (pa == -1) /* dl_prio() doesn't work because of stop_class above */
> +             return !dl_time_before(a->dl.deadline, b->dl.deadline);
> +
> +     vruntime = b->se.vruntime;
> +     if (core_cmp) {
> +             vruntime -= task_cfs_rq(b)->min_vruntime;
> +             vruntime += task_cfs_rq(a)->min_vruntime;
> +     }
> +     if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */
> +             return !((s64)(a->se.vruntime - vruntime) <= 0);
> +
> +     return false;
> +}
> +
> +static inline bool cpu_prio_less(struct task_struct *a, struct task_struct 
> *b)
> +{
> +     return __prio_less(a, b, false);
> +}
> +
> +static inline bool core_prio_less(struct task_struct *a, struct task_struct 
> *b)
> +{
> +     return __prio_less(a, b, true);
> +}
> +
> +static inline bool __sched_core_less(struct task_struct *a, struct 
> task_struct *b)
> +{
> +     if (a->core_cookie < b->core_cookie)
> +             return true;
> +
> +     if (a->core_cookie > b->core_cookie)
> +             return false;
> +
> +     /* flip prio, so high prio is leftmost */
> +     if (cpu_prio_less(b, a))
> +             return true;
> +
> +     return false;
> +}
> +

A minor nitpick.  I find keeping the vruntime base readjustment in
core_prio_less probably is more straight forward rather than pass a
core_cmp bool around.

Tim


diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 455e7ecc2f48..5917fb85669b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -100,15 +87,13 @@ static inline struct cfs_rq *task_cfs_rq(struct 
task_struct *p)
  */
 
 /* real prio, less is less */
-static inline bool __prio_less(struct task_struct *a, struct task_struct *b, 
bool core_cmp)
+static inline bool __prio_less(struct task_struct *a, struct task_struct *b, 
u64 vruntime)
 {
-       u64 vruntime;
-
        int pa = __task_prio(a), pb = __task_prio(b);
 
        trace_printk("(%s/%d;%d,%Lu,%Lu) ?< (%s/%d;%d,%Lu,%Lu)\n",
-                    a->comm, a->pid, pa, a->se.vruntime, a->dl.deadline,
-                    b->comm, b->pid, pa, b->se.vruntime, b->dl.deadline);
+                       a->comm, a->pid, pa, a->se.vruntime, a->dl.deadline,
+                       b->comm, b->pid, pa, b->se.vruntime, b->dl.deadline);
 
        if (-pa < -pb)
                return true;
@@ -119,11 +104,6 @@ static inline bool __prio_less(struct task_struct *a, 
struct task_struct *b, boo
        if (pa == -1) /* dl_prio() doesn't work because of stop_class above */
                return !dl_time_before(a->dl.deadline, b->dl.deadline);
 
-       vruntime = b->se.vruntime;
-       if (core_cmp) {
-               vruntime -= task_cfs_rq(b)->min_vruntime;
-               vruntime += task_cfs_rq(a)->min_vruntime;
-       }
        if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */
                return !((s64)(a->se.vruntime - vruntime) <= 0);
 
@@ -132,12 +112,17 @@ static inline bool __prio_less(struct task_struct *a, 
struct task_struct *b, boo
 
 static inline bool cpu_prio_less(struct task_struct *a, struct task_struct *b)
 {
-       return __prio_less(a, b, false);
+       return __prio_less(a, b, b->se.vruntime);
 }
 
 static inline bool core_prio_less(struct task_struct *a, struct task_struct *b)
 {
-       return __prio_less(a, b, true);
+       u64 vruntime = b->se.vruntime;
+
+       vruntime -= task_cfs_rq(b)->min_vruntime;
+       vruntime += task_cfs_rq(a)->min_vruntime;
+
+       return __prio_less(a, b, vruntime);
 }
 
 static inline bool __sched_core_less(struct task_struct *a, struct task_struct 
*b)