[lkml]   [2012]   [Sep]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 08/11] perf tool: precise mode requires exclude_guest

On 06.09.12 00:07:52, Peter Zijlstra wrote:
> On Wed, 2012-09-05 at 09:43 -0600, David Ahern wrote:
> > We need to require exclude_guest when using precise attribute with perf
> > else all running VMs on Intel-based servers will crash. I do not have an
> > AMD based server to even attempt the preferred solution.

do you have a perf tool patch ready that enables exclude_guest per
default for precise events? I have ibs kernel code that returns EINVAL
in this case. Current perf tool should then fall back by sending
another syscall with the exclude_guest modifier disabled. This should
work for ibs. Testing your patch wouln't be an effort for me.

To prevent Intel-based servers from crashing, pebs should be only
enabled if the exclude_guest modifier is enabled. I guess there is
already kernel code to prevent this, but didn't look at the sources.

To prevent probing the kernel with syscalls to detect pmu features, I
suggested some time ago to introduce


or so similar to /proc/cpuinfo:flags. Any opinions on that?

There is also the option to emulate exclude_guest for ibs in
software. So far I didn't have the time to look at this. We could
still add this in the future. Since we need to fix current mainline
anyway where such a patch wouldn't go in for v3.6, I will send my
current ibs kernel fixes I mentioned above next days. It would be
great to test this also with your patch.



Advanced Micro Devices, Inc.
Operating System Research Center

 \ /
  Last update: 2012-09-06 22:43    [W:0.101 / U:7.312 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site