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sched/vtime: Record CPU under seqcount for kcpustat needs

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In order to compute the kcpustat delta on a nohz CPU, we'll need to
fetch the task running on that target. Checking that its vtime
state snapshot actually refers to the relevant target involves recording
that CPU under the seqcount locked on task switch.

This is a step toward making kcpustat moving forward on full nohz CPUs.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J . Wysocki <rjw@rjwysocki.net>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
Link: https://lkml.kernel.org/r/20191016025700.31277-2-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Frederic Weisbecker 2019-10-16 04:56:47 +02:00 committed by Ingo Molnar
parent b8c9636140
commit 802f4a827f
2 changed files with 4 additions and 0 deletions
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1
include/linux/sched.h
View file

@ -259,6 +259,7 @@ struct vtime {
seqcount_t seqcount;
unsigned long long starttime;
enum vtime_state state;
unsigned int cpu;
u64 utime;
u64 stime;
u64 gtime;

3
kernel/sched/cputime.c
View file

@ -818,6 +818,7 @@ void vtime_task_switch_generic(struct task_struct *prev)
else
__vtime_account_kernel(prev, vtime);
vtime->state = VTIME_INACTIVE;
vtime->cpu = -1;
write_seqcount_end(&vtime->seqcount);
vtime = &current->vtime;
@ -825,6 +826,7 @@ void vtime_task_switch_generic(struct task_struct *prev)
write_seqcount_begin(&vtime->seqcount);
vtime->state = VTIME_SYS;
vtime->starttime = sched_clock();
vtime->cpu = smp_processor_id();
write_seqcount_end(&vtime->seqcount);
}
@ -837,6 +839,7 @@ void vtime_init_idle(struct task_struct *t, int cpu)
write_seqcount_begin(&vtime->seqcount);
vtime->state = VTIME_SYS;
vtime->starttime = sched_clock();
vtime->cpu = cpu;
write_seqcount_end(&vtime->seqcount);
local_irq_restore(flags);
}