lkml.org 
[lkml]   [2014]   [Jul]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] sched_clock: Track monotonic raw clock
On Fri, Jul 18, 2014 at 06:43:39PM +0100, Pawel Moll wrote:
> This change is trying to make the sched clock "similar" to the
> monotonic raw one.
>
> The main goal is to provide some kind of unification between time
> flow in kernel and in user space, mainly to achieve correlation
> between perf timestamps and clock_gettime(CLOCK_MONOTONIC_RAW).
> This has been suggested by Ingo and John during the latest
> discussion (of many, we tried custom ioctl, custom clock etc.)
> about this:
>
> http://thread.gmane.org/gmane.linux.kernel/1611683/focus=1612554
>
> For now I focused on the generic sched clock implementation,
> but similar approach can be applied elsewhere.
>
> Initially I just wanted to copy epoch from monotonic to sched
> clock at update_clock(), but this can cause the sched clock
> going backwards in certain corner cases, eg. when the sched
> clock "increases faster" than the monotonic one. I believe
> it's a killer issue, but feel free to ridicule me if I worry
> too much :-)

But on hardware using generic sched_clock we use the exact same hardware
as the regular timekeeping, right?

So we could start off with the same offset/mult/shift and never deviate,
or is that a silly question?, I've never really looked at the generic
sched_clock stuff too closely.


\
 
 \ /
  Last update: 2014-07-18 21:41    [W:1.465 / U:0.120 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site