From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Frederic Weisbecker <frederic@kernel.org>,
Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>,
Thomas Gleixner <tglx@linutronix.de>,
Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>,
Phil Auld <pauld@redhat.com>, Sasha Levin <sashal@kernel.org>,
mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org
Subject: [PATCH MANUALSEL 5.15 1/9] sched/cputime: Fix getrusage(RUSAGE_THREAD) with nohz_full
Date: Mon, 13 Dec 2021 09:19:34 -0500 [thread overview]
Message-ID: <20211213141944.352249-1-sashal@kernel.org> (raw)
From: Frederic Weisbecker <frederic@kernel.org>
[ Upstream commit e7f2be115f0746b969c0df14c0d182f65f005ca5 ]
getrusage(RUSAGE_THREAD) with nohz_full may return shorter utime/stime
than the actual time.
task_cputime_adjusted() snapshots utime and stime and then adjust their
sum to match the scheduler maintained cputime.sum_exec_runtime.
Unfortunately in nohz_full, sum_exec_runtime is only updated once per
second in the worst case, causing a discrepancy against utime and stime
that can be updated anytime by the reader using vtime.
To fix this situation, perform an update of cputime.sum_exec_runtime
when the cputime snapshot reports the task as actually running while
the tick is disabled. The related overhead is then contained within the
relevant situations.
Reported-by: Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Acked-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20211026141055.57358-3-frederic@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/sched/cputime.h | 5 +++--
kernel/sched/cputime.c | 12 +++++++++---
2 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/include/linux/sched/cputime.h b/include/linux/sched/cputime.h
index 6c9f19a33865a..ce3c58286062c 100644
--- a/include/linux/sched/cputime.h
+++ b/include/linux/sched/cputime.h
@@ -18,15 +18,16 @@
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
-extern void task_cputime(struct task_struct *t,
+extern bool task_cputime(struct task_struct *t,
u64 *utime, u64 *stime);
extern u64 task_gtime(struct task_struct *t);
#else
-static inline void task_cputime(struct task_struct *t,
+static inline bool task_cputime(struct task_struct *t,
u64 *utime, u64 *stime)
{
*utime = t->utime;
*stime = t->stime;
+ return false;
}
static inline u64 task_gtime(struct task_struct *t)
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 872e481d5098c..9392aea1804e5 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -615,7 +615,8 @@ void task_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
.sum_exec_runtime = p->se.sum_exec_runtime,
};
- task_cputime(p, &cputime.utime, &cputime.stime);
+ if (task_cputime(p, &cputime.utime, &cputime.stime))
+ cputime.sum_exec_runtime = task_sched_runtime(p);
cputime_adjust(&cputime, &p->prev_cputime, ut, st);
}
EXPORT_SYMBOL_GPL(task_cputime_adjusted);
@@ -828,19 +829,21 @@ u64 task_gtime(struct task_struct *t)
* add up the pending nohz execution time since the last
* cputime snapshot.
*/
-void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
+bool task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
{
struct vtime *vtime = &t->vtime;
unsigned int seq;
u64 delta;
+ int ret;
if (!vtime_accounting_enabled()) {
*utime = t->utime;
*stime = t->stime;
- return;
+ return false;
}
do {
+ ret = false;
seq = read_seqcount_begin(&vtime->seqcount);
*utime = t->utime;
@@ -850,6 +853,7 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
if (vtime->state < VTIME_SYS)
continue;
+ ret = true;
delta = vtime_delta(vtime);
/*
@@ -861,6 +865,8 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
else
*utime += vtime->utime + delta;
} while (read_seqcount_retry(&vtime->seqcount, seq));
+
+ return ret;
}
static int vtime_state_fetch(struct vtime *vtime, int cpu)
--
2.33.0
next reply other threads:[~2021-12-13 14:20 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-13 14:19 Sasha Levin [this message]
2021-12-13 14:19 ` [PATCH MANUALSEL 5.15 2/9] timers/nohz: Last resort update jiffies on nohz_full IRQ entry Sasha Levin
2021-12-13 14:19 ` [PATCH MANUALSEL 5.15 3/9] KVM: VMX: clear vmx_x86_ops.sync_pir_to_irr if APICv is disabled Sasha Levin
2021-12-13 14:27 ` Paolo Bonzini
2021-12-13 14:19 ` [PATCH MANUALSEL 5.15 4/9] KVM: SEV: do not take kvm->lock when destroying Sasha Levin
2021-12-13 14:27 ` Paolo Bonzini
2021-12-13 14:19 ` [PATCH MANUALSEL 5.15 5/9] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE Sasha Levin
2021-12-13 14:27 ` Paolo Bonzini
2021-12-13 14:19 ` [PATCH MANUALSEL 5.15 6/9] KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN Sasha Levin
2021-12-13 14:28 ` Paolo Bonzini
2021-12-13 14:19 ` [PATCH MANUALSEL 5.15 7/9] KVM: selftests: Avoid KVM_SET_CPUID2 after KVM_RUN in hyperv_features test Sasha Levin
2021-12-13 14:28 ` Paolo Bonzini
2021-12-13 14:19 ` [PATCH MANUALSEL 5.15 8/9] KVM: downgrade two BUG_ONs to WARN_ON_ONCE Sasha Levin
2021-12-13 14:28 ` Paolo Bonzini
2021-12-13 14:19 ` [PATCH MANUALSEL 5.15 9/9] x86/kvm: remove unused ack_notifier callbacks Sasha Levin
2021-12-13 14:28 ` Paolo Bonzini
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