Messages in this thread | | | From | Pan Xinhui <> | Subject | [PATCH 0/3] implement vcpu preempted check | Date | Mon, 27 Jun 2016 13:41:27 -0400 |
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This is to fix some bad issues on an over-committed guest.
test-caes: perf record -a perf bench sched messaging -g 400 -p && perf report
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
osq takes a long time with preemption disabled which is really bad.
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. Even there is need_resched(), it did not help on such scenario.
we may also need fix other XXX_spin_on_owner later based on this patch set. these spin_on_onwer variant cause rcu stall.
Pan Xinhui (3): powerpc/spinlock: support vcpu preempted check locking/osq: Drop the overload of osq_lock() kernel/sched: introduce vcpu preempted check interface
arch/powerpc/include/asm/lppaca.h | 6 ++++++ arch/powerpc/include/asm/spinlock.h | 15 +++++++++++++++ include/linux/sched.h | 9 +++++++++ kernel/locking/osq_lock.c | 16 +++++++++++++++- 4 files changed, 45 insertions(+), 1 deletion(-)
-- 2.4.11
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