From: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
virtualization@lists.linux-foundation.org,
linux-s390@vger.kernel.org,
xen-devel-request@lists.xenproject.org, kvm@vger.kernel.org,
xen-devel@lists.xenproject.org, x86@kernel.org
Cc: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
mingo@redhat.com, peterz@infradead.org,
paulmck@linux.vnet.ibm.com, will.deacon@arm.com,
kernellwp@gmail.com, jgross@suse.com, pbonzini@redhat.com,
bsingharora@gmail.com, boqun.feng@gmail.com,
borntraeger@de.ibm.com, rkrcmar@redhat.com,
David.Laight@ACULAB.COM,
Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Subject: [PATCH v6 03/11] kernel/locking: Drop the overload of {mutex, rwsem}_spin_on_owner
Date: Fri, 28 Oct 2016 04:11:19 -0400 [thread overview]
Message-ID: <1477642287-24104-4-git-send-email-xinhui.pan@linux.vnet.ibm.com> (raw)
In-Reply-To: <1477642287-24104-1-git-send-email-xinhui.pan@linux.vnet.ibm.com>
An over-committed guest with more vCPUs than pCPUs has a heavy overload in
the two spin_on_owner. This blames on the lock holder preemption issue.
Kernel has an interface bool vcpu_is_preempted(int cpu) to see if a vCPU is
currently running or not. So break the spin loops on true condition.
test-case:
perf record -a perf bench sched messaging -g 400 -p && perf report
before patch:
20.68% sched-messaging [kernel.vmlinux] [k] mutex_spin_on_owner
8.45% sched-messaging [kernel.vmlinux] [k] mutex_unlock
4.12% sched-messaging [kernel.vmlinux] [k] system_call
3.01% sched-messaging [kernel.vmlinux] [k] system_call_common
2.83% sched-messaging [kernel.vmlinux] [k] copypage_power7
2.64% sched-messaging [kernel.vmlinux] [k] rwsem_spin_on_owner
2.00% sched-messaging [kernel.vmlinux] [k] osq_lock
after patch:
9.99% sched-messaging [kernel.vmlinux] [k] mutex_unlock
5.28% sched-messaging [unknown] [H] 0xc0000000000768e0
4.27% sched-messaging [kernel.vmlinux] [k] __copy_tofrom_user_power7
3.77% sched-messaging [kernel.vmlinux] [k] copypage_power7
3.24% sched-messaging [kernel.vmlinux] [k] _raw_write_lock_irq
3.02% sched-messaging [kernel.vmlinux] [k] system_call
2.69% sched-messaging [kernel.vmlinux] [k] wait_consider_task
Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Tested-by: Juergen Gross <jgross@suse.com>
---
kernel/locking/mutex.c | 15 +++++++++++++--
kernel/locking/rwsem-xadd.c | 16 +++++++++++++---
2 files changed, 26 insertions(+), 5 deletions(-)
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index a70b90d..82108f5 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -236,7 +236,13 @@ bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
*/
barrier();
- if (!owner->on_cpu || need_resched()) {
+ /*
+ * Use vcpu_is_preempted to detech lock holder preemption issue
+ * and break. vcpu_is_preempted is a macro defined by false if
+ * arch does not support vcpu preempted check,
+ */
+ if (!owner->on_cpu || need_resched() ||
+ vcpu_is_preempted(task_cpu(owner))) {
ret = false;
break;
}
@@ -261,8 +267,13 @@ static inline int mutex_can_spin_on_owner(struct mutex *lock)
rcu_read_lock();
owner = READ_ONCE(lock->owner);
+
+ /*
+ * As lock holder preemption issue, we both skip spinning if task is not
+ * on cpu or its cpu is preempted
+ */
if (owner)
- retval = owner->on_cpu;
+ retval = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));
rcu_read_unlock();
/*
* if lock->owner is not set, the mutex owner may have just acquired
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index 2337b4b..0897179 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -336,7 +336,11 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
goto done;
}
- ret = owner->on_cpu;
+ /*
+ * As lock holder preemption issue, we both skip spinning if task is not
+ * on cpu or its cpu is preempted
+ */
+ ret = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));
done:
rcu_read_unlock();
return ret;
@@ -362,8 +366,14 @@ static noinline bool rwsem_spin_on_owner(struct rw_semaphore *sem)
*/
barrier();
- /* abort spinning when need_resched or owner is not running */
- if (!owner->on_cpu || need_resched()) {
+ /*
+ * abort spinning when need_resched or owner is not running or
+ * owner's cpu is preempted. vcpu_is_preempted is a macro
+ * defined by false if arch does not support vcpu preempted
+ * check
+ */
+ if (!owner->on_cpu || need_resched() ||
+ vcpu_is_preempted(task_cpu(owner))) {
rcu_read_unlock();
return false;
}
--
2.4.11
next prev parent reply other threads:[~2016-10-28 4:25 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-28 8:11 [PATCH v6 00/11] implement vcpu preempted check Pan Xinhui
2016-10-28 8:11 ` [PATCH v6 01/11] kernel/sched: introduce vcpu preempted check interface Pan Xinhui
2016-10-28 8:11 ` [PATCH v6 02/11] locking/osq: Drop the overload of osq_lock() Pan Xinhui
2016-10-29 16:52 ` Davidlohr Bueso
2016-10-30 14:39 ` Pan Xinhui
2016-10-28 8:11 ` Pan Xinhui [this message]
2016-10-28 8:11 ` [PATCH v6 04/11] powerpc/spinlock: support vcpu preempted check Pan Xinhui
2016-10-28 8:11 ` [PATCH v6 05/11] s390/spinlock: Provide vcpu_is_preempted Pan Xinhui
2016-10-28 8:11 ` [PATCH v6 06/11] x86, paravirt: Add interface to support kvm/xen vcpu preempted check Pan Xinhui
2016-10-28 8:11 ` [PATCH v6 07/11] KVM: Introduce kvm_write_guest_offset_cached Pan Xinhui
2016-10-28 8:11 ` [PATCH v6 08/11] x86, kvm/x86.c: support vcpu preempted check Pan Xinhui
2016-10-28 8:11 ` [PATCH v6 09/11] x86, kernel/kvm.c: " Pan Xinhui
2016-10-28 8:11 ` [PATCH v6 10/11] x86, xen: " Pan Xinhui
2016-10-28 19:43 ` [Xen-devel] " Konrad Rzeszutek Wilk
2016-10-29 4:26 ` Pan Xinhui
2016-10-28 8:11 ` [PATCH v6 11/11] Documentation: virtual: kvm: Support " Pan Xinhui
2016-10-28 9:57 ` [PATCH v6 00/11] implement " Paolo Bonzini
2016-10-28 19:38 ` [Xen-devel] " Konrad Rzeszutek Wilk
2016-10-29 4:37 ` Pan Xinhui
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