Messages in this thread | | | Date | Wed, 20 Oct 2021 12:37:32 +0200 | Subject | Re: [PATCH v3 3/3] KVM: vCPU kick tax cut for running vCPU | From | Paolo Bonzini <> |
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On 20/10/21 12:02, Wanpeng Li wrote: >> +#ifdef CONFIG_PREEMPT_RCU >> + /* The cost of rcu_read_lock() is nontrivial for preemptable RCU. */ >> + if (!rcuwait_active(w)) >> + return ret; >> +#endif >> + >> + rcu_read_lock(); >> + >> task = rcu_dereference(w->task); >> if (task) >> ret = wake_up_process(task); >> >> (If you don't, rcu_read_lock is essentially preempt_disable() and it >> should not have a large overhead). You still need the memory barrier >> though, in order to avoid missed wakeups; shameless plug for my >> article athttps://lwn.net/Articles/847481/. > You are right, the cost of rcu_read_lock() for preemptable RCU > introduces too much overhead, do you want to send a separate patch?
Yes, I'll take care of this. Thanks!
Paolo
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