Messages in this thread | | | Subject | Re: [RFC PATCH] MIPS: Oprofile: Drop support | From | Matt Redfearn <> | Date | Fri, 4 May 2018 10:54:32 +0100 |
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Hi Robert,
On 04/05/18 10:30, Robert Richter wrote: > On 24.04.18 14:15:58, Matt Redfearn wrote: >> On 24/04/18 14:05, James Hogan wrote: >>> On Tue, Apr 24, 2018 at 01:55:54PM +0100, Matt Redfearn wrote: >>>> Since it appears that MIPS oprofile support is currently broken, core >>>> oprofile is not getting many updates and not as many architectures >>>> implement support for it compared to perf, remove the MIPS support. >>> >>> That sounds reasonable to me. Any idea how long its been broken? >> >> Sorry, not yet. I haven't yet looked into where/how it's broken that would >> narrow that down... > > oprofile moved to perf syscall as kernel i/f with version 1.0.0. The
OK interesting. I guess this was the point at which MIPS' current Kconfig rule which only allows building oprofile or perf into a kernel broke oprofile userspace.
> opcontrol script that was using the oprofile kernel i/f was removed: > > https://sourceforge.net/p/oprofile/oprofile/ci/0c142c3a096d3e9ec42cc9b0ddad994fea60d135/ > > Thus, cpus that do not support the perf syscall are no longer > supported by 1.x releases. > > https://sourceforge.net/p/oprofile/oprofile/ci/797d01dea0b82dbbdb0c21112a3de75990e011d2/ > > For those remainings there is still version 0.9.x available (tagged > PRE_RELEASE_1_0). > > I am undecided whether removing oprofile kernel i/f falls under the > rule of "never break user space" here. Strictly seen, yes it breaks > those remainings. So if the perf syscall is not available as an > alternative, the oprofile kernel support shouldn't be removed.
perf is available for MIPS and supports many more CPU types than oprofile. oprofile userspace seemingly has been broken since 1.0.0 - removing oprofile support from the MIPS kernel would not break it more thatn it already is, but of course it would be better to fix it - if it is still useful and people still use it. That is the question that I was looking for answers for with this RFC - whether to spend the time & effort to fix oprofile, or if it can be removed since everyone uses perf.
Thanks, Matt
> > -Robert >
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