On 23.08.2018 16:59, Anders Magnusson wrote: > Den 2018-08-23 kl. 16:48, skrev Kamil Rytarowski: >> On 23.08.2018 16:28, Anders Magnusson wrote: >>> Den 2018-08-23 kl. 15:53, skrev Maxime Villard: >>>> Le 17/08/2018 à 17:42, Kamil Rytarowski a écrit : >>>>> On 17.08.2018 17:13, Maxime Villard wrote: >>>>>> Note that I'm talking about the kernel gprof, and not the userland >>>>>> gprof. >>>>>> In terms of kernel profiling, it's not nonsensical to say that >>>>>> since we >>>>>> support ARM and x86 in tprof, we can cover 99% of the MI parts of >>>>>> whatever architecture. From then on, being able to profile the >>>>>> kernel on >>>>>> other architectures has very little interest. >>>>> Speaking realistically, probably all the recent software-based kernel >>>>> profiling was done with DTrace. >>>> Yes. So I will proceed. >>>> >>>> Note that the removal of the kernel gprof implies the removal of kgmon. >>> Just checking: How will it work for ports like vax? >>> When searching for bottlenecks I normally use gprof/kgmon. I don't know >>> anything about DTrace, hence the question. >>> >>> -- Ragge >> There is no support of DTrace for vax and probably there won't be one. >> Also probably DTrace is not a final solution per se (DTrace is described >> as step backwards by people such as Brendan Gregg).. but we are working >> on better toolchain support to open more possibilities such as XRay. >> >> Regarding vax there might be bottlenecks in MD code, but DTrace is a >> decent one for MI code on supported ports. > Hm, so this means that we will be without kernel profiling support at > all on non-DTrace architectures? > I'm not too happy about that by obvious reasons. > > It do not work to profile code paths on other architectures, since what > takes time is very different. > And yes, it is not the MD code that is the case, it's the MI code. > > I may have missed something, but why remove something that works without > replacing it with something new? > Only have profiling on a few ports do not sound very clever to me. > > -- Ragge > > Evaluating this situation we have to be aware that this description could be reversed and there are ports without meaningful (or any) gprof support. Observing that all the useful profiling is already done with DTrace, we can remove complexity from the kernel with negligible cost.
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