Re: [PATCH v2 1/6] powerpc/perf: Define big-endian version of perf_mem_data_src

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 1/6] powerpc/perf: Define big-endian version of perf_mem_data_src
Date	2017-03-06 16:30 +0100
Message-ID	<ti2Ke-1BJ-7@gated-at.bofh.it> (permalink)
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On Mon, Mar 06, 2017 at 02:59:07PM +0000, David Laight wrote:
> From: Peter Zijlstra
> > Sent: 06 March 2017 11:22
> > To: Madhavan Srinivasan
> > Cc: Wang Nan; Alexander Shishkin; linux-kernel@vger.kernel.org; Arnaldo Carvalho de Melo; Alexei
> > Starovoitov; Ingo Molnar; Stephane Eranian; Sukadev Bhattiprolu; linuxppc-dev@lists.ozlabs.org
> > Subject: Re: [PATCH v2 1/6] powerpc/perf: Define big-endian version of perf_mem_data_src
> > 
> > On Mon, Mar 06, 2017 at 04:13:08PM +0530, Madhavan Srinivasan wrote:
> > > From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
> > >
> > > perf_mem_data_src is an union that is initialized via the ->val field
> > > and accessed via the bitmap fields. For this to work on big endian
> > > platforms, we also need a big-endian represenation of perf_mem_data_src.
> > 
> > Doesn't this break interpreting the data on a different endian machine?
> 
> Best to avoid bitfields if you ever care about the bit order.

Too late for that. But perf tool has quite a bit of code to muck fields
between different endians. With the full intent that generation on one
machine is readable by another.

Thread

[PATCH v2 0/6] powerpc/perf: Export memory hierarchy level Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2017-03-06 11:50 +0100
  [PATCH v2 2/6] powerpc/perf: Export memory hierarchy info to user space Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2017-03-06 11:50 +0100
    Re: [PATCH v2 2/6] powerpc/perf: Export memory hierarchy info to  user space Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2017-03-13 20:30 +0100
  [PATCH v2 3/6] powerpc/perf: Support to export MMCRA[TEC*] field to userspace Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2017-03-06 11:50 +0100
  [PATCH v2 5/6] powerpc/perf: Support to export SIERs bit in Power9 Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2017-03-06 11:50 +0100
  [PATCH v2 1/6] powerpc/perf: Define big-endian version of perf_mem_data_src Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2017-03-06 11:50 +0100
    Re: [PATCH v2 1/6] powerpc/perf: Define big-endian version of  perf_mem_data_src Peter Zijlstra <peterz@infradead.org> - 2017-03-06 12:30 +0100
      RE: [PATCH v2 1/6] powerpc/perf: Define big-endian version of  perf_mem_data_src David Laight <David.Laight@ACULAB.COM> - 2017-03-06 16:10 +0100
        Re: [PATCH v2 1/6] powerpc/perf: Define big-endian version of  perf_mem_data_src Peter Zijlstra <peterz@infradead.org> - 2017-03-06 16:30 +0100
      Re: [PATCH v2 1/6] powerpc/perf: Define big-endian version of  perf_mem_data_src Peter Zijlstra <peterz@infradead.org> - 2017-03-07 13:50 +0100
        Re: [PATCH v2 1/6] powerpc/perf: Define big-endian version of  perf_mem_data_src Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2017-03-13 12:20 +0100
          Re: [PATCH v2 1/6] powerpc/perf: Define big-endian version of  perf_mem_data_src Peter Zijlstra <peterz@infradead.org> - 2017-03-13 14:00 +0100
      Re: [PATCH v2 1/6] powerpc/perf: Define big-endian version of  perf_mem_data_src Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2017-03-07 13:50 +0100
  [PATCH v2 6/6] powerpc/perf: Add Power8 mem_access event to sysfs Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2017-03-06 15:10 +0100
  [PATCH v2 4/6] powerpc/perf: Support to export SIERs bit in Power8 Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2017-03-06 16:00 +0100

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