Messages in this thread |  | | Date | Thu, 05 Dec 2013 07:33:20 -0700 | From | David Ahern <> | Subject | Re: [PATCH 4/4] perf trace: Add option to specify machine type |
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On 12/5/13, 6:50 AM, Arnaldo Carvalho de Melo wrote: > Em Wed, Dec 04, 2013 at 07:41:42PM -0700, David Ahern escreveu: >> Perhaps there is a better way to do this; I could not think of one and >> I don't see any field in the tracepoint that can be leveraged. So ... >> >> perf-trace autodetects the machine type (e.g., i386, x86_64, etc) via >> libaudit. > > And that means that using perf.data files from another machine, say, > ARM, will produce completely bogus results :-\
Indeed all offline analysis of trace data is wrong because it uses the arch of the machine running perf. I am not hitting that problem, but analysis on box.
> > We need a way to store this info in the perf.data header, i.e. use the > same algorithm that libaudit uses in audit_detect_machine() (and set the > open_id as well, btw) at 'perf record' time and store it somewhere. > > What we have now that could be used? > > Lets see: > > [acme@zoo linux]$ perf report | grep 'arch' > # arch : x86_64 > [acme@zoo linux]$ > > Would that be enough? Stephane?
That fixes one part -- using the arch in the file to translate system calls in the file.
But it is a per process problem: Some are 32-bit; others are 64-bit. I was hoping there was some option at the syscall entry level to tag the bitness. And then there is the problem of needing a solution that works from RHEL6 forward. This patch at least allows me to have sensible data until something more clever is thought of.
David
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