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Bug #1689

CMK_TIMER_USE_PPC64 inaccurate with variable clock speeds

Added by Phil Miller 10 months ago. Updated 5 months ago.

Status:
In Progress
Priority:
Normal
Assignee:
Category:
Machine Layers
Target version:
Start date:
04/30/2017
Due date:
% Done:

0%


Description

The pami-linux-ppc64le machine layer is defaulting to CMK_TIMER_USE_PPC64

src/arch/pami-linux-ppc64le/conv-mach.h:#define CMK_TIMER_USE_PPC64 1

This timer assumes a constant clock speed, which hasn't been true for a long time so projections traces are pretty useless.

Fix the code to do what's necessary to get accurate wall times from the fast intrinsic techniques.


Related issues

Copied from Charm++ - Bug #1544: CMK_TIMER_USE_PPC64 inaccurate with variable clock speeds Merged 04/30/2017

History

#1 Updated by Phil Miller 10 months ago

  • Copied from Bug #1544: CMK_TIMER_USE_PPC64 inaccurate with variable clock speeds added

#2 Updated by Sam White 6 months ago

  • Status changed from Implemented to New

Not sure why this was marked "implemented"...

#3 Updated by Ronak Buch 6 months ago

  • Status changed from New to In Progress

#4 Updated by Ronak Buch 6 months ago

I tried reproducing this on a POWER8 machine and wasn't able to, the timing looked normal.

However, reading through some POWER9 docs makes it seem that there's no guarantee that the time base register update frequency is constant (https://ibm.ent.box.com/s/1hzcwkwf8rbju5h9iyf44wm94amnlcrv. page 898-899, section 6.1).

#5 Updated by Jim Phillips 6 months ago

It was marked implemented because of https://charm.cs.illinois.edu/gerrit/#/c/3075/

#6 Updated by Sam White 5 months ago

That patch was merged, so should this issue be marked 'merged'? If not, maybe retarget to 6.9.1

#7 Updated by Ronak Buch 5 months ago

  • Target version changed from 6.9.0 to 6.9.1

I talked to Bilge to get more information about the timers on POWER and if there was any chance that the timer can be guaranteed to update at a fixed frequency. She didn't know and said that she would get back to me with more information.

For now, I'm pushing this to 6.9.1.

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