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From: Ingo Molnar <mingo@kernel.org>
To: Eric Dumazet <edumazet@google.com>
Cc: x86 <x86@kernel.org>, lkml <linux-kernel@vger.kernel.org>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Hugh Dickins <hughd@google.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH v3 1/2] x86, msr: allow rdmsr_safe_on_cpu() to schedule
Date: Sat, 24 Mar 2018 09:09:46 +0100	[thread overview]
Message-ID: <20180324080946.3db4xdkl5i6jx2rc@gmail.com> (raw)
In-Reply-To: <20180323215818.127774-1-edumazet@google.com>


* Eric Dumazet <edumazet@google.com> 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 section,
> then waiting for the answer can consume hundreds of usec.
> 
> Converts rdmsr_safe_on_cpu() to use a completion instead
> of busy polling.
> 
> Overall daemon cpu usage was reduced by 35 %,
> and latencies caused by msr_read() disappeared.

What "daemon" is this and why is it reading MSRs?

Thanks,

	Ingo

  parent reply	other threads:[~2018-03-24  8:09 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-23 21:58 [PATCH v3 1/2] x86, msr: allow rdmsr_safe_on_cpu() to schedule Eric Dumazet
2018-03-23 21:58 ` [PATCH v3 2/2] x86, cpuid: allow cpuid_read() " Eric Dumazet
2018-03-23 22:17   ` H. Peter Anvin
2018-03-24  1:01     ` Eric Dumazet
2018-03-25 22:11       ` H. Peter Anvin
2018-03-27 10:10   ` [tip:x86/cleanups] x86/cpuid: Allow " tip-bot for Eric Dumazet
2018-03-24  8:09 ` Ingo Molnar [this message]
2018-03-24 10:50   ` [PATCH v3 1/2] x86, msr: allow rdmsr_safe_on_cpu() " Thomas Gleixner
2018-03-24 14:29   ` Eric Dumazet
2018-03-25 14:12     ` Borislav Petkov
2018-03-26  1:21       ` H. Peter Anvin
2018-03-26  6:40       ` Ingo Molnar
     [not found]         ` <CANn89iKy_jVpBvAebJFm1UKVKfG=p+R4B1tXmC4waeK7YzZh2g@mail.gmail.com>
2018-03-26 14:23           ` Thomas Gleixner
2018-03-27  9:36             ` Ingo Molnar
2018-03-27 10:10 ` [tip:x86/cleanups] x86/msr: Allow " tip-bot for Eric Dumazet

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