From: Peter Zijlstra <peterz@infradead.org>
To: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: linux-kernel@vger.kernel.org, Len Brown <len.brown@intel.com>,
Frederic Weisbecker <frederic@kernel.org>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH RFC] x86 / CPU: Add cpu isolation flag for avoiding disturbance from aperfmperf IPI
Date: Thu, 25 Apr 2019 14:38:04 +0200 [thread overview]
Message-ID: <20190425123804.GU4038@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <8b54ebf5-7daf-2760-7210-e0e945014c9e@yandex-team.ru>
On Thu, Apr 25, 2019 at 03:27:12PM +0300, Konstantin Khlebnikov wrote:
> On 25.04.2019 14:45, Peter Zijlstra wrote:
> > On Thu, Apr 25, 2019 at 01:46:51PM +0300, Konstantin Khlebnikov wrote:
> > > Sensitive workloads like DPDK polling do not like any interrupts.
> > >
> > > This patch adds flag 'freq' for boot option 'isolcpu': isolcpu=freq,<cpus>.
> > >
> > > Users like show_cpuinfo() fallback to frequency from generic cpufreq
> > > policy if arch-specific requesting method returns 0.
> >
> > Then don't touch that sysfs file?
>
> What sysfs file?
/sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq
> I mean many applications read /proc/cpuinfo and this triggers IPI to all cpus.
Argh, I missed it was wired into that too :/
> > I really hate having an option for just this.
> >
>
> This could be generalized to 'isolate cpu from unnecessary IPI'.
> Something like mm pagevec drain also could be avoided.
Well, that should be a default feature of nohz full, no additional flags
required.
prev parent reply other threads:[~2019-04-25 12:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-25 10:46 Konstantin Khlebnikov
2019-04-25 11:45 ` Peter Zijlstra
2019-04-25 12:27 ` Konstantin Khlebnikov
2019-04-25 12:38 ` Peter Zijlstra [this message]
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