Re: [PATCH RFC] x86 / CPU: Add cpu isolation flag for avoiding disturbance from aperfmperf IPI
From: Peter Zijlstra
Date: Thu Apr 25 2019 - 08:38:13 EST
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?
> 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