Re: [PATCH v2 1/2] x86, msr: add rdmsr_safe_on_cpu_resched() and use it in msr_read()

2018-03-23 Thread Eric Dumazet
On 03/23/2018 02:27 PM, Thomas Gleixner wrote: > > Looking at all call sites. None of them is performance critical and all of > them are in preemptible context. > > So we simply can switch the rdmsr_safe_on_cpu() implementation over to wait > mode completely. SGTM, thanks for looking, I will se

Re: [PATCH v2 1/2] x86, msr: add rdmsr_safe_on_cpu_resched() and use it in msr_read()

2018-03-23 Thread Thomas Gleixner
On Mon, 19 Mar 2018, Eric Dumazet wrote: > I noticed high latencies caused by a daemon periodically reading > various MSR on all cpus. KASAN kernels would see ~10ms latencies > simply reading one MSR. Even without KASAN, sending IPI to CPU > in deep sleep state or blocking hard IRQ in a a long sec

[PATCH v2 1/2] x86, msr: add rdmsr_safe_on_cpu_resched() and use it in msr_read()

2018-03-19 Thread Eric Dumazet
I noticed high latencies caused by a daemon periodically reading various MSR on all cpus. KASAN kernels would see ~10ms latencies simply reading one MSR. Even without KASAN, sending IPI to CPU in deep sleep state or blocking hard IRQ in a a long section, then waiting for the answer can consume hund