sched/cputime: Correctly support generic vtime idle time

Currently whether generic vtime is running or not, the idle cputime is
fetched from the nohz accounting.

However generic vtime already does its own idle cputime accounting. Only
the kernel stat accessors are not plugged to support it.

Read the idle generic vtime cputime when it's running, this will allow to
later more clearly split nohz and vtime cputime accounting.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Link: https://patch.msgid.link/20260508131647.43868-5-frederic@kernel.org

diff --git a/include/linux/vtime.h b/include/linux/vtime.h
index 29dd5b91dd7d6684ae4f9092e3a6c8566ef3dd3e..336875bea767701295787b965b0a39eb2162df6a 100644 (file)
--- a/include/linux/vtime.h
+++ b/include/linux/vtime.h
@@ -10,7 +10,6 @@
  */
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
 extern void vtime_account_kernel(struct task_struct *tsk);
-extern void vtime_account_idle(struct task_struct *tsk);
 #endif /* !CONFIG_VIRT_CPU_ACCOUNTING */
 
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
@@ -27,7 +26,13 @@ static inline void vtime_guest_exit(struct task_struct *tsk) { }
 static inline void vtime_init_idle(struct task_struct *tsk, int cpu) { }
 #endif
 
+static inline bool vtime_generic_enabled_cpu(int cpu)
+{
+       return context_tracking_enabled_cpu(cpu);
+}
+
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
+extern void vtime_account_idle(struct task_struct *tsk);
 extern void vtime_account_irq(struct task_struct *tsk, unsigned int offset);
 extern void vtime_account_softirq(struct task_struct *tsk);
 extern void vtime_account_hardirq(struct task_struct *tsk);
@@ -74,7 +79,7 @@ static inline bool vtime_accounting_enabled(void)
 
 static inline bool vtime_accounting_enabled_cpu(int cpu)
 {
-       return context_tracking_enabled_cpu(cpu);
+       return vtime_generic_enabled_cpu(cpu);
 }
 
 static inline bool vtime_accounting_enabled_this_cpu(void)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index caaaf0a04ced99ed0f6453f3829f1ef4b2a13717..815d0f772cae32d4a522c8e1ffcb4e6b0553c6f0 100644 (file)
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -773,9 +773,9 @@ void vtime_guest_exit(struct task_struct *tsk)
 }
 EXPORT_SYMBOL_GPL(vtime_guest_exit);
 
-void vtime_account_idle(struct task_struct *tsk)
+static void __vtime_account_idle(struct vtime *vtime)
 {
-       account_idle_time(get_vtime_delta(&tsk->vtime));
+       account_idle_time(get_vtime_delta(vtime));
 }
 
 void vtime_task_switch_generic(struct task_struct *prev)
@@ -784,7 +784,7 @@ void vtime_task_switch_generic(struct task_struct *prev)
 
        write_seqcount_begin(&vtime->seqcount);
        if (vtime->state == VTIME_IDLE)
-               vtime_account_idle(prev);
+               __vtime_account_idle(vtime);
        else
                __vtime_account_kernel(prev, vtime);
        vtime->state = VTIME_INACTIVE;
@@ -926,6 +926,7 @@ static int kcpustat_field_vtime(u64 *cpustat,
                                int cpu, u64 *val)
 {
        struct vtime *vtime = &tsk->vtime;
+       struct rq *rq = cpu_rq(cpu);
        unsigned int seq;
 
        do {
@@ -967,6 +968,14 @@ static int kcpustat_field_vtime(u64 *cpustat,
                        if (state == VTIME_GUEST && task_nice(tsk) > 0)
                                *val += vtime->gtime + vtime_delta(vtime);
                        break;
+               case CPUTIME_IDLE:
+                       if (state == VTIME_IDLE && !atomic_read(&rq->nr_iowait))
+                               *val += vtime_delta(vtime);
+                       break;
+               case CPUTIME_IOWAIT:
+                       if (state == VTIME_IDLE && atomic_read(&rq->nr_iowait) > 0)
+                               *val += vtime_delta(vtime);
+                       break;
                default:
                        break;
                }
@@ -1029,8 +1038,8 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
                *dst = *src;
                cpustat = dst->cpustat;
 
-               /* Task is sleeping, dead or idle, nothing to add */
-               if (state < VTIME_SYS)
+               /* Task is sleeping or dead, nothing to add */
+               if (state < VTIME_IDLE)
                        continue;
 
                delta = vtime_delta(vtime);
@@ -1039,15 +1048,17 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
                 * Task runs either in user (including guest) or kernel space,
                 * add pending nohz time to the right place.
                 */
-               if (state == VTIME_SYS) {
+               switch (state) {
+               case VTIME_SYS:
                        cpustat[CPUTIME_SYSTEM] += vtime->stime + delta;
-               } else if (state == VTIME_USER) {
+                       break;
+               case VTIME_USER:
                        if (task_nice(tsk) > 0)
                                cpustat[CPUTIME_NICE] += vtime->utime + delta;
                        else
                                cpustat[CPUTIME_USER] += vtime->utime + delta;
-               } else {
-                       WARN_ON_ONCE(state != VTIME_GUEST);
+                       break;
+               case VTIME_GUEST:
                        if (task_nice(tsk) > 0) {
                                cpustat[CPUTIME_GUEST_NICE] += vtime->gtime + delta;
                                cpustat[CPUTIME_NICE] += vtime->gtime + delta;
@@ -1055,6 +1066,15 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
                                cpustat[CPUTIME_GUEST] += vtime->gtime + delta;
                                cpustat[CPUTIME_USER] += vtime->gtime + delta;
                        }
+                       break;
+               case VTIME_IDLE:
+                       if (atomic_read(&cpu_rq(cpu)->nr_iowait) > 0)
+                               cpustat[CPUTIME_IOWAIT] += delta;
+                       else
+                               cpustat[CPUTIME_IDLE] += delta;
+                       break;
+               default:
+                       WARN_ON_ONCE(1);
                }
        } while (read_seqcount_retry(&vtime->seqcount, seq));
 

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 171393367b5c1e3ecd395634b44b4ca4a9c41b56..597c3a0682e709db4965038f1769b32f578f8725 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -783,9 +783,10 @@ static void tick_nohz_start_idle(struct tick_sched *ts)
        sched_clock_idle_sleep_event();
 }
 
-static u64 get_cpu_sleep_time_us(struct tick_sched *ts, ktime_t *sleeptime,
+static u64 get_cpu_sleep_time_us(int cpu, enum cpu_usage_stat idx, ktime_t *sleeptime,
                                 bool compute_delta, u64 *last_update_time)
 {
+       struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
        ktime_t now, idle;
        unsigned int seq;
 
@@ -796,6 +797,11 @@ static u64 get_cpu_sleep_time_us(struct tick_sched *ts, ktime_t *sleeptime,
        if (last_update_time)
                *last_update_time = ktime_to_us(now);
 
+       if (vtime_generic_enabled_cpu(cpu)) {
+               idle = kcpustat_field(idx, cpu);
+               return ktime_to_us(idle);
+       }
+
        do {
                ktime_t delta = 0;
 
@@ -834,7 +840,7 @@ u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
 {
        struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 
-       return get_cpu_sleep_time_us(ts, &ts->idle_sleeptime,
+       return get_cpu_sleep_time_us(cpu, CPUTIME_IDLE, &ts->idle_sleeptime,
                                     !nr_iowait_cpu(cpu), last_update_time);
 }
 EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
@@ -860,7 +866,7 @@ u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
 {
        struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 
-       return get_cpu_sleep_time_us(ts, &ts->iowait_sleeptime,
+       return get_cpu_sleep_time_us(cpu, CPUTIME_IOWAIT, &ts->iowait_sleeptime,
                                     nr_iowait_cpu(cpu), last_update_time);
 }
 EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);