misc/181346: [hwpmc] Sandy Bridge Xeon - workaround required for some perf events

[adrian chadd]

>Number:         181346
>Category:       misc
>Synopsis:       [hwpmc] Sandy Bridge Xeon - workaround required for some perf events
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Aug 16 20:30:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     adrian chadd
>Release:        
>Organization:
>Environment:
>Description:
There's a workaround required for some events on Sandy bridge Xeon hardware.

http://software.intel.com/en-us/articles/performance-monitoring-on-intel-xeon-processor-e5-family

Here's the workaround packaged up in a linux-specific python script. ugh.

https://github.com/andikleen/pmu-tools/blob/master/latego.py

I have no idea about the specifics of the workaround; only that we should likely add support to hwpmc to do this.

>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
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