Commit 802f4a82 authored Oct 16, 2019 by Frederic Weisbecker Committed by Ingo Molnar Oct 29, 2019

sched/vtime: Record CPU under seqcount for kcpustat needs



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>

parent b8c96361

include/linux/sched.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -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;

kernel/sched/cputime.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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);
		}

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