Messages in this thread | | | Date | Tue, 22 Apr 2014 23:24:24 +0200 | Subject | Re: mapping instructions to dynamic languages like java, python, ruby | From | Stephane Eranian <> |
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On Tue, Apr 22, 2014 at 10:54 PM, Andi Kleen <andi@firstfloor.org> wrote: >> Does anyone have any thoughts or experience on this? > > perf has a JIT interface today, but it's extremely primitive > and only supports symbols. Clearly it could be done better. > > Various JITs (e.g. Java) have special debug interfaces for this. > > Various non perf profilers support it too. e.g. Vtune has a special > API for it: > https://software.intel.com/sites/default/files/jit_profiling_api_lin_0.pdf > > Essentially you would need to write a JIT specific adapter > that translates to perf format. Or emulate the Vtune interface > and reuse existing Vtune adaptations. > > perf record needs some kind of side band interface where the JIT adapter > can report to it: > - symbols > - the assembler code (so it can be shown) > - source lines > - report any changes when JITed code changes > Forgot to mention that my implementation does go all the way to jitted code assembly view via perf annotate + source view.
So it does cover all aspects.
As for attaching to a running JIT, this again needs some cooperation from JIT environment.
> Then perf record could put that information into the perf.data. > > In theory that information could be passed through the kernel, > but just using some user protocol (unix sockets or files) would be > likely enough. The current interface uses files in /tmp. > I would likely change that, it's not clear even if it's secure. > > It's likely a substantial project. > > It would be even useful for the kernel, as the kernel does JITing > itself these days. > > -Andi
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