Re: [PATCH 4/6] nohz: support PR_DATAPLANE_QUIESCE

From: Peter Zijlstra
Date: Tue May 12 2015 - 05:34:25 EST

On Fri, May 08, 2015 at 01:58:45PM -0400, Chris Metcalf wrote:
> This prctl() flag for PR_SET_DATAPLANE sets a mode that requires the
> kernel to quiesce any pending timer interrupts prior to returning
> to userspace. When running with this mode set, sys calls (and page
> faults, etc.) can be inordinately slow. However, user applications
> that want to guarantee that no unexpected interrupts will occur
> (even if they call into the kernel) can set this flag to guarantee
> that semantics.

Currently people hot-unplug and hot-plug the CPU to do this. Obviously
that's a wee bit horrible :-)

Not sure if a prctl like this is any better though. This is a CPU
properly not a process one.

ISTR people talking about 'quiesce' sysfs file, along side the hotplug
stuff, I can't quite remember.

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