Messages in this thread | | | Date | Sun, 25 Jun 2017 23:43:02 +0900 | From | Namhyung Kim <> | Subject | Re: [PATCH/RFC 9/9] perf record: Add --module-dir option |
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On Fri, Jun 23, 2017 at 11:45:24AM -0300, Arnaldo Carvalho de Melo wrote: > Em Fri, Jun 23, 2017 at 02:48:27PM +0900, Namhyung Kim escreveu: > > Currently perf only searches module binaries on the canonical > > directory (/lib/modules/`uname -r`). But sometimes user needs to load > > local modules. These cannot be copied to the build-id cache since long > > name (i.e. real path) of DSOs was not set. > > > This patch fixes the problem by adding a new --module-dir option so that > > perf can record modules in the directory. > > > +++ b/tools/perf/Documentation/perf-record.txt > > @@ -480,6 +480,9 @@ Implies --tail-synthesize. > > +--module-dir=PATH:: > > +Directory name where extra modules are located. > > > +++ b/tools/perf/builtin-record.c > > @@ -1671,6 +1671,8 @@ static struct option __record_options[] = { > > "Parse options then exit"), > > OPT_BOOLEAN(0, "use-kcore", &symbol_conf.use_kcore, > > "Use /proc/kcore for object code"), > > + OPT_STRING(0, "module-dir", &symbol_conf.extra_module_path, "path", > > + "directory name where extra modules are located"), > > OPT_END() > > }; > > > > +++ b/tools/perf/util/machine.c > > @@ -1117,7 +1118,19 @@ static int machine__set_modules_path(struct machine *machine) > > machine->root_dir, version); > > free(version); > > > > - return map_groups__set_modules_path_dir(&machine->kmaps, modules_path, 0); > > + ret = map_groups__set_modules_path_dir(&machine->kmaps, modules_path, 0); > > + if (ret < 0) > > + return ret; > > + > > + if (symbol_conf.extra_module_path) { > > + snprintf(modules_path, sizeof(modules_path), "%s/%s", > > + machine->root_dir, symbol_conf.extra_module_path); > > + > > + ret = map_groups__set_modules_path_dir(&machine->kmaps, > > + modules_path, 0); > > What if we have samples in a module that is in the canonical dir _and_ > samples in a module in this extra_module_path? Shouldn't we have > something like vmlinux_path, but for modules? Where you can add entries > in that path? > > I'm ok with adding entries to where module files are looked up, with > semantics similar to $PATH in a shell, i.e. entries added via > --module-path (rename of your --module-dir) will take precedence over > the canonical dir (/lib/modules/`uname -r`).
I think we can check the build-id in sysfs and binaries in both directories. If the sysfs is not avaiable (i.e. the module is unloaded in the meantime), the precedence can be used IMHO.
Thanks, Namhyung
> > But for the future I think we should try to get a PERF_RECORD_MMAP that > will allow reloading modules during a 'perf record' session when a > module gets reloaded, I thought about using existing tracepoints, but... > > [root@jouet ~]# cat /sys/kernel/debug/tracing/events/module/module_load/format > name: module_load > ID: 370 > format: > field:unsigned short common_type; offset:0; size:2; signed:0; > field:unsigned char common_flags; offset:2; size:1; signed:0; > field:unsigned char common_preempt_count; offset:3; size:1; signed:0; > field:int common_pid; offset:4; size:4; signed:1; > > field:unsigned int taints; offset:8; size:4; signed:0; > field:__data_loc char[] name; offset:12; size:4; signed:1; > > print fmt: "%s %s", __get_str(name), __print_flags(REC->taints, "", { (1UL << 0), "P" }, { (1UL << 12), "O" }, { (1UL << 1), "F" }, { (1UL << 10), "C" }, { (1UL << 13), "E" }) > [root@jouet ~]# perf trace --no-syscalls --event module:module_load modprobe ppp > modprobe: FATAL: Module ppp not found in directory /lib/modules/4.12.0-rc4+ > [root@jouet ~]# perf trace --no-syscalls --event module:module_load modprobe e1000 > 0.000 module:module_load:e1000 ) > [root@jouet ~]# > > It just gets us the module name, not the file from what it is loaded, bummer :-\ > > Something like: > > diff --git a/kernel/module.c b/kernel/module.c > index 4a3665f8f837..50e9718a141d 100644 > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -3739,6 +3739,7 @@ static int load_module(struct load_info *info, const char __user *uargs, > > /* Done! */ > trace_module_load(mod); > + perf_event_mmap_mod(mod); > > return do_init_module(mod); > > ---------- > > struct module *mod has: > > mod->name: "e1000" > mod->debug->filename: /lib/modules/4.11.0-rc8+/kernel/drivers/net/ethernet/intel/e1000/e1000.ko > > and at that point we also have load_info, htat has ELF headers where we could extract the build-id > and insert it in a field in a new PERF_RECORD_MMAP3 record :-) > > perf_event_mmap_mod() would be modelled after perf_event_mmap(vma), but getting what > it needs not from the vma present in a sys_mmap() but from struct module and load_info. > > - Arnaldo > > > + } > > + > > + return ret; > > } > > int __weak arch__fix_module_text_start(u64 *start __maybe_unused, > > const char *name __maybe_unused) > > diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h > > index 88361eeae813..59370ceb87c4 100644 > > --- a/tools/perf/util/symbol.h > > +++ b/tools/perf/util/symbol.h > > @@ -124,7 +124,8 @@ struct symbol_conf { > > const char *vmlinux_name, > > *kallsyms_name, > > *source_prefix, > > - *field_sep; > > + *field_sep, > > + *extra_module_path; > > const char *default_guest_vmlinux_name, > > *default_guest_kallsyms, > > *default_guest_modules; > > -- > > 2.13.1
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