* [PATCH MANUALSEL 5.4 1/2] sched/cputime: Fix getrusage(RUSAGE_THREAD) with nohz_full
@ 2021-12-13 14:20 Sasha Levin
2021-12-13 14:20 ` [PATCH MANUALSEL 5.4 2/2] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE Sasha Levin
0 siblings, 1 reply; 3+ messages in thread
From: Sasha Levin @ 2021-12-13 14:20 UTC (permalink / raw)
To: linux-kernel, stable
Cc: Frederic Weisbecker, Hasegawa Hitomi, Thomas Gleixner,
Masayoshi Mizuma, Phil Auld, Sasha Levin, mingo, peterz,
juri.lelli, vincent.guittot
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 46ed4e1383e21..a7ebf0d8e369f 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -666,7 +666,8 @@ 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);
@@ -859,19 +860,21 @@ 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;
@@ -881,6 +884,7 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
if (vtime->state == VTIME_INACTIVE || is_idle_task(t))
continue;
+ ret = true;
delta = vtime_delta(vtime);
/*
@@ -892,5 +896,7 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
else if (vtime->state == VTIME_SYS)
*stime += vtime->stime + delta;
} while (read_seqcount_retry(&vtime->seqcount, seq));
+
+ return ret;
}
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */
--
2.33.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH MANUALSEL 5.4 2/2] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE
2021-12-13 14:20 [PATCH MANUALSEL 5.4 1/2] sched/cputime: Fix getrusage(RUSAGE_THREAD) with nohz_full Sasha Levin
@ 2021-12-13 14:20 ` Sasha Levin
2021-12-13 14:22 ` Paolo Bonzini
0 siblings, 1 reply; 3+ messages in thread
From: Sasha Levin @ 2021-12-13 14:20 UTC (permalink / raw)
To: linux-kernel, stable
Cc: Vitaly Kuznetsov, Sean Christopherson, Paolo Bonzini,
Sasha Levin, shuah, kvm, linux-kselftest
From: Vitaly Kuznetsov <vkuznets@redhat.com>
[ Upstream commit 908fa88e420f30dde6d80f092795a18ec72ca6d3 ]
With the elevated 'KVM_CAP_MAX_VCPUS' value kvm_create_max_vcpus test
may hit RLIMIT_NOFILE limits:
# ./kvm_create_max_vcpus
KVM_CAP_MAX_VCPU_ID: 4096
KVM_CAP_MAX_VCPUS: 1024
Testing creating 1024 vCPUs, with IDs 0...1023.
/dev/kvm not available (errno: 24), skipping test
Adjust RLIMIT_NOFILE limits to make sure KVM_CAP_MAX_VCPUS fds can be
opened. Note, raising hard limit ('rlim_max') requires CAP_SYS_RESOURCE
capability which is generally not needed to run kvm selftests (but without
raising the limit the test is doomed to fail anyway).
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20211123135953.667434-1-vkuznets@redhat.com>
[Skip the test if the hard limit can be raised. - Paolo]
Reviewed-by: Sean Christopherson <seanjc@google.com>
Tested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../selftests/kvm/kvm_create_max_vcpus.c | 30 +++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
index 231d79e57774e..cfe75536d8a55 100644
--- a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
+++ b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
@@ -12,6 +12,7 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#include <sys/resource.h>
#include "test_util.h"
@@ -43,10 +44,39 @@ int main(int argc, char *argv[])
{
int kvm_max_vcpu_id = kvm_check_cap(KVM_CAP_MAX_VCPU_ID);
int kvm_max_vcpus = kvm_check_cap(KVM_CAP_MAX_VCPUS);
+ /*
+ * Number of file descriptors reqired, KVM_CAP_MAX_VCPUS for vCPU fds +
+ * an arbitrary number for everything else.
+ */
+ int nr_fds_wanted = kvm_max_vcpus + 100;
+ struct rlimit rl;
printf("KVM_CAP_MAX_VCPU_ID: %d\n", kvm_max_vcpu_id);
printf("KVM_CAP_MAX_VCPUS: %d\n", kvm_max_vcpus);
+ /*
+ * Check that we're allowed to open nr_fds_wanted file descriptors and
+ * try raising the limits if needed.
+ */
+ TEST_ASSERT(!getrlimit(RLIMIT_NOFILE, &rl), "getrlimit() failed!");
+
+ if (rl.rlim_cur < nr_fds_wanted) {
+ rl.rlim_cur = nr_fds_wanted;
+ if (rl.rlim_max < nr_fds_wanted) {
+ int old_rlim_max = rl.rlim_max;
+ rl.rlim_max = nr_fds_wanted;
+
+ int r = setrlimit(RLIMIT_NOFILE, &rl);
+ if (r < 0) {
+ printf("RLIMIT_NOFILE hard limit is too low (%d, wanted %d)\n",
+ old_rlim_max, nr_fds_wanted);
+ exit(KSFT_SKIP);
+ }
+ } else {
+ TEST_ASSERT(!setrlimit(RLIMIT_NOFILE, &rl), "setrlimit() failed!");
+ }
+ }
+
/*
* Upstream KVM prior to 4.8 does not support KVM_CAP_MAX_VCPU_ID.
* Userspace is supposed to use KVM_CAP_MAX_VCPUS as the maximum ID
--
2.33.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH MANUALSEL 5.4 2/2] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE
2021-12-13 14:20 ` [PATCH MANUALSEL 5.4 2/2] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE Sasha Levin
@ 2021-12-13 14:22 ` Paolo Bonzini
0 siblings, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2021-12-13 14:22 UTC (permalink / raw)
To: Sasha Levin, linux-kernel, stable
Cc: Vitaly Kuznetsov, Sean Christopherson, shuah, kvm, linux-kselftest
On 12/13/21 15:20, Sasha Levin wrote:
> From: Vitaly Kuznetsov <vkuznets@redhat.com>
>
> [ Upstream commit 908fa88e420f30dde6d80f092795a18ec72ca6d3 ]
>
> With the elevated 'KVM_CAP_MAX_VCPUS' value kvm_create_max_vcpus test
> may hit RLIMIT_NOFILE limits:
>
> # ./kvm_create_max_vcpus
> KVM_CAP_MAX_VCPU_ID: 4096
> KVM_CAP_MAX_VCPUS: 1024
> Testing creating 1024 vCPUs, with IDs 0...1023.
> /dev/kvm not available (errno: 24), skipping test
>
> Adjust RLIMIT_NOFILE limits to make sure KVM_CAP_MAX_VCPUS fds can be
> opened. Note, raising hard limit ('rlim_max') requires CAP_SYS_RESOURCE
> capability which is generally not needed to run kvm selftests (but without
> raising the limit the test is doomed to fail anyway).
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> Message-Id: <20211123135953.667434-1-vkuznets@redhat.com>
> [Skip the test if the hard limit can be raised. - Paolo]
> Reviewed-by: Sean Christopherson <seanjc@google.com>
> Tested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> .../selftests/kvm/kvm_create_max_vcpus.c | 30 +++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
> index 231d79e57774e..cfe75536d8a55 100644
> --- a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
> +++ b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
> @@ -12,6 +12,7 @@
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> +#include <sys/resource.h>
>
> #include "test_util.h"
>
> @@ -43,10 +44,39 @@ int main(int argc, char *argv[])
> {
> int kvm_max_vcpu_id = kvm_check_cap(KVM_CAP_MAX_VCPU_ID);
> int kvm_max_vcpus = kvm_check_cap(KVM_CAP_MAX_VCPUS);
> + /*
> + * Number of file descriptors reqired, KVM_CAP_MAX_VCPUS for vCPU fds +
> + * an arbitrary number for everything else.
> + */
> + int nr_fds_wanted = kvm_max_vcpus + 100;
> + struct rlimit rl;
>
> printf("KVM_CAP_MAX_VCPU_ID: %d\n", kvm_max_vcpu_id);
> printf("KVM_CAP_MAX_VCPUS: %d\n", kvm_max_vcpus);
>
> + /*
> + * Check that we're allowed to open nr_fds_wanted file descriptors and
> + * try raising the limits if needed.
> + */
> + TEST_ASSERT(!getrlimit(RLIMIT_NOFILE, &rl), "getrlimit() failed!");
> +
> + if (rl.rlim_cur < nr_fds_wanted) {
> + rl.rlim_cur = nr_fds_wanted;
> + if (rl.rlim_max < nr_fds_wanted) {
> + int old_rlim_max = rl.rlim_max;
> + rl.rlim_max = nr_fds_wanted;
> +
> + int r = setrlimit(RLIMIT_NOFILE, &rl);
> + if (r < 0) {
> + printf("RLIMIT_NOFILE hard limit is too low (%d, wanted %d)\n",
> + old_rlim_max, nr_fds_wanted);
> + exit(KSFT_SKIP);
> + }
> + } else {
> + TEST_ASSERT(!setrlimit(RLIMIT_NOFILE, &rl), "setrlimit() failed!");
> + }
> + }
> +
> /*
> * Upstream KVM prior to 4.8 does not support KVM_CAP_MAX_VCPU_ID.
> * Userspace is supposed to use KVM_CAP_MAX_VCPUS as the maximum ID
>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-12-13 14:20 [PATCH MANUALSEL 5.4 1/2] sched/cputime: Fix getrusage(RUSAGE_THREAD) with nohz_full Sasha Levin
2021-12-13 14:20 ` [PATCH MANUALSEL 5.4 2/2] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE Sasha Levin
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