From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ivan Babrou Subject: Re: eBPF program symbols in perf top Date: Wed, 28 Nov 2018 16:20:03 -0800 Message-ID: References: <20181127133054.GE15747@kernel.org> <20181128130438.GB31608@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20181128130438.GB31608@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: arnaldo.melo@gmail.com Cc: linux-perf-users@vger.kernel.org, daniel@iogearbox.net, ast@kernel.org, davem@davemloft.net, dsahern@gmail.com, linux-kernel@vger.kernel.org List-Id: linux-perf-users.vger.kernel.org On Wed, Nov 28, 2018 at 5:04 AM Arnaldo Carvalho de Melo wrote: > > Em Tue, Nov 27, 2018 at 11:41:19PM -0800, Ivan Babrou escreveu: > > Hey Arnaldo, > > > > Thanks for the quick response. I've tried your patch and it works as > > expected with perf top. > > Ok, I'll add the patch to my perf/core branch with your Reported-by and > Tested-by, is that ok with you? Sounds good to me. > > What are the reasons for not giving kallsyms precedence at this moment? > > The use of vmlinux for these things predates having many of the code > modifications that are performed in a live kernel these days, also > pre-dates eBPF, etc, etc, so using vmlinux, when found, was better > because ELF symtabs are more expressive, kallsyms have just the start of > a symbol, for instance, etc. > > Having that said, with the advent of things like Intel PT, etc using > /proc/kcore + /proc/kallsyms became a requirement, there is even code to > stash copies of those in ~/.debug/ for post processing (off-site using > 'perf archive' even, etc). > > I _think_ that switch to using /proc/kallsyms as default now is becoming > a requirement, just haven't thought thru all possible implications of > doing that. I'm looking forward to having it enabled by default, also happy to apply a patch and start using it internally when you have it. > I don't recall if there is a way to set kallsyms precedence in > ~/.perfconfig, have to look at that. > > - Arnaldo > > > On Tue, Nov 27, 2018 at 5:30 AM Arnaldo Carvalho de Melo > > wrote: > > > > > > Em Mon, Nov 26, 2018 at 04:21:15PM -0800, Ivan Babrou escreveu: > > > > It's possible to see eBPF programs in "perf report" and "perf script" > > > > started with "--kallsyms=/proc/kallsyms", if net.core.bpf_jit_kallsyms > > > > sysctl is set to 1. However, it's not possible to pass "--kallsyms" to > > > > "perf top". > > > > > > > > > So, the first step, I think, is to check if having 'perf top > > > --kallsyms=..." would help, i.e. to check the patch that introduced > > > '--kallsyms' to 'perf report' and see if that would be difficult to have > > > the same functionality in 'perf top', the cset where it is introduced > > > is: > > > > > > b226a5a72901b ("perf report: Allow user to specify path to kallsyms file" > > > > > > Below is the resulting patch, can you please check if with that you get > > > the result you want? We can then go from there to some simplification, > > > perhaps give precedence to kallsyms. > > > > > > diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt > > > index 808b664343c9..44d89fb9c788 100644 > > > --- a/tools/perf/Documentation/perf-top.txt > > > +++ b/tools/perf/Documentation/perf-top.txt > > > @@ -70,6 +70,9 @@ Default is to monitor all CPUS. > > > --ignore-vmlinux:: > > > Ignore vmlinux files. > > > > > > +--kallsyms=:: > > > + kallsyms pathname > > > + > > > -m :: > > > --mmap-pages=:: > > > Number of mmap data pages (must be a power of two) or size > > > diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c > > > index aa0c73e57924..1252d1759064 100644 > > > --- a/tools/perf/builtin-top.c > > > +++ b/tools/perf/builtin-top.c > > > @@ -1289,6 +1289,8 @@ int cmd_top(int argc, const char **argv) > > > "file", "vmlinux pathname"), > > > OPT_BOOLEAN(0, "ignore-vmlinux", &symbol_conf.ignore_vmlinux, > > > "don't load vmlinux even if found"), > > > + OPT_STRING(0, "kallsyms", &symbol_conf.kallsyms_name, > > > + "file", "kallsyms pathname"), > > > OPT_BOOLEAN('K', "hide_kernel_symbols", &top.hide_kernel_symbols, > > > "hide kernel symbols"), > > > OPT_CALLBACK('m', "mmap-pages", &opts->mmap_pages, "pages", > > -- > > - Arnaldo