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Groups > linux.kernel > #1432802
| From | Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v2 3/4] locking/osq: Drop the overload of osq_lock() |
| Date | 2016-06-28 12:50 +0200 |
| Message-ID | <rOYKC-5Nk-39@gated-at.bofh.it> (permalink) |
| References | <rOYKC-5Nk-11@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
An over-committed guest with more vCPUs than pCPUs has a heavy overload in
osq_lock().
This is because vCPU A hold the osq lock and yield out, vCPU B wait per_cpu
node->locked to be set. IOW, vCPU B wait vCPU A to run and unlock the osq
lock.
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:
18.09% sched-messaging [kernel.vmlinux] [k] osq_lock
12.28% sched-messaging [kernel.vmlinux] [k] rwsem_spin_on_owner
5.27% sched-messaging [kernel.vmlinux] [k] mutex_unlock
3.89% sched-messaging [kernel.vmlinux] [k] wait_consider_task
3.64% sched-messaging [kernel.vmlinux] [k] _raw_write_lock_irq
3.41% sched-messaging [kernel.vmlinux] [k] mutex_spin_on_owner.is
2.49% sched-messaging [kernel.vmlinux] [k] system_call
after 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
Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
kernel/locking/osq_lock.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
index 05a3785..39d1385 100644
--- a/kernel/locking/osq_lock.c
+++ b/kernel/locking/osq_lock.c
@@ -21,6 +21,11 @@ static inline int encode_cpu(int cpu_nr)
return cpu_nr + 1;
}
+static inline int node_cpu(struct optimistic_spin_node *node)
+{
+ return node->cpu - 1;
+}
+
static inline struct optimistic_spin_node *decode_cpu(int encoded_cpu_val)
{
int cpu_nr = encoded_cpu_val - 1;
@@ -118,8 +123,11 @@ bool osq_lock(struct optimistic_spin_queue *lock)
while (!READ_ONCE(node->locked)) {
/*
* If we need to reschedule bail... so we can block.
+ * 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 (need_resched())
+ if (need_resched() || vcpu_is_preempted(node_cpu(node->prev)))
goto unqueue;
cpu_relax_lowlatency();
--
2.4.11
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[PATCH v2 0/4] implement vcpu preempted check Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-28 12:50 +0200
[PATCH v2 1/4] kernel/sched: introduce vcpu preempted check interface Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-28 12:50 +0200
[PATCH v2 3/4] locking/osq: Drop the overload of osq_lock() Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-28 12:50 +0200
[PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-28 12:50 +0200
Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check Wanpeng Li <kernellwp@gmail.com> - 2016-07-05 12:00 +0200
Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-07-06 07:00 +0200
Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check Wanpeng Li <kernellwp@gmail.com> - 2016-07-06 08:50 +0200
Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check Peter Zijlstra <peterz@infradead.org> - 2016-07-06 10:00 +0200
Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check Wanpeng Li <kernellwp@gmail.com> - 2016-07-06 10:40 +0200
Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-07-06 12:20 +0200
Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check Balbir Singh <bsingharora@gmail.com> - 2016-07-06 13:00 +0200
[PATCH v2 4/4] kernel/locking: Drop the overload of {mutex,rwsem}_spin_on_owner Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-28 12:50 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Peter Zijlstra <peterz@infradead.org> - 2016-07-06 09:00 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Juergen Gross <jgross@suse.com> - 2016-07-06 09:50 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Peter Zijlstra <peterz@infradead.org> - 2016-07-06 10:20 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Juergen Gross <jgross@suse.com> - 2016-07-06 10:40 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Paolo Bonzini <pbonzini@redhat.com> - 2016-07-06 14:50 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Christian Borntraeger <borntraeger@de.ibm.com> - 2016-07-06 19:00 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-07-06 12:10 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Paolo Bonzini <pbonzini@redhat.com> - 2016-07-06 12:50 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Wanpeng Li <kernellwp@gmail.com> - 2016-07-06 14:10 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Paolo Bonzini <pbonzini@redhat.com> - 2016-07-06 14:40 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Wanpeng Li <kernellwp@gmail.com> - 2016-07-06 15:10 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Wanpeng Li <kernellwp@gmail.com> - 2016-07-07 10:50 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Peter Zijlstra <peterz@infradead.org> - 2016-07-07 11:50 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Wanpeng Li <kernellwp@gmail.com> - 2016-07-07 12:20 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Wanpeng Li <kernellwp@gmail.com> - 2016-07-07 12:30 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Peter Zijlstra <peterz@infradead.org> - 2016-07-07 13:20 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Peter Zijlstra <peterz@infradead.org> - 2016-07-07 13:10 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Peter Zijlstra <peterz@infradead.org> - 2016-07-07 13:10 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Peter Zijlstra <peterz@infradead.org> - 2016-07-07 13:30 +0200
Re: [PATCH v2 0/4] implement vcpu preempted check Peter Zijlstra <peterz@infradead.org> - 2016-07-06 14:10 +0200
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