Messages in this thread | | | Subject | Re: [RFC PATCH] MIPS: Oprofile: Drop support | From | Matt Redfearn <> | Date | Fri, 4 May 2018 13:59:32 +0100 |
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Hi Robert,
On 04/05/18 13:27, Robert Richter wrote: > On 04.05.18 12:03:12, Matt Redfearn wrote: >>> As said, oprofile version 0.9.x is still available for cpus that do >>> not support perf. What is the breakage? >> >> The breakage I originally set out to fix was the MT support in perf. >> https://www.linux-mips.org/archives/linux-mips/2018-04/msg00259.html >> >> Since the perf code shares so much copied code from oprofile, those same >> issues exist in oprofile and ought to be addressed. But as newer oprofile >> userspace does not use the (MIPS) kernel oprofile code, then we could, >> perhaps, just remove it (as per the RFC). That would break legacy tools >> (0.9.x) though... > > Those support perf: > > (CPU_MIPS32 || CPU_MIPS64 || CPU_R10000 || CPU_SB1 || CPU_CAVIUM_OCTEON || CPU_XLP || CPU_LOONGSON3) > > Here is the total list of CPU_*: > > $ git grep -h config.CPU_ arch/mips/ | sort -u | wc -l > 79
To be fair, that list for oprofile is not much different:
arch/mips/oprofile/Makefile:
oprofile-$(CONFIG_CPU_MIPS32) += op_model_mipsxx.o oprofile-$(CONFIG_CPU_MIPS64) += op_model_mipsxx.o oprofile-$(CONFIG_CPU_R10000) += op_model_mipsxx.o oprofile-$(CONFIG_CPU_SB1) += op_model_mipsxx.o oprofile-$(CONFIG_CPU_XLR) += op_model_mipsxx.o oprofile-$(CONFIG_CPU_LOONGSON2) += op_model_loongson2.o oprofile-$(CONFIG_CPU_LOONGSON3) += op_model_loongson3.o
However, since those are generally CPU families rather than individual CPUs, the number of models supported by each framework tells a different story:
git grep -h ops.cpu_type arch/mips/oprofile | wc -l 20
git grep -h pmu.name arch/mips/kernel/perf_event* | wc -l 17
The difference is mainly older CPUs - M14Kc, 20K, loongson1, etc. But yes you are right dropping it would kill profiling for them - that being the case I guess oprofile should remain and instead just remove support for the MT capable CPUs (34K, interAptiv) which are all supported by perf.
Thanks, Matt
> > The comparisation might not be accurate, but at least gives a hint > that there are many cpus not supporting perf. You would drop profiling > support at al to them. > > If it is too hard to also fix the oprofile code (code duplication > seems the main issue here), then it would be also ok to blacklist > newer cpus to enable oprofile kernel code (where it is broken). > > -Robert >
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