Messages in this thread |  | | | Date | Tue, 28 Jul 2009 03:22:34 +0200 | | From | Frederic Weisbecker <> | | Subject | Re: [PATCH] tracing/events: Add module tracepoints |
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On Mon, Jul 27, 2009 at 09:41:46AM +0800, Li Zefan wrote: > Frederic Weisbecker wrote: > > On Tue, Jul 21, 2009 at 04:56:33PM +0800, Li Zefan wrote: > >> Add trace points to trace module_load, module_free, module_get, > >> module_put and module_request, and use trace_event facility > >> to get the trace output. > >> > >> Here's the sample output: > >> > >> TASK-PID CPU# TIMESTAMP FUNCTION > >> | | | | | > >> <...>-42 [000] 1.758380: module_request: fb0 wait=1 call_site=fb_open > >> ... > >> <...>-60 [000] 3.269403: module_load: scsi_wait_scan > >> <...>-60 [000] 3.269432: module_put: scsi_wait_scan call_site=sys_init_module refcnt=0 > >> <...>-61 [001] 3.273168: module_free: scsi_wait_scan > >> ... > >> <...>-1021 [000] 13.836081: module_load: sunrpc > >> <...>-1021 [000] 13.840589: module_put: sunrpc call_site=sys_init_module refcnt=-1 > >> <...>-1027 [000] 13.848098: module_get: sunrpc call_site=try_module_get refcnt=0 > >> <...>-1027 [000] 13.848308: module_get: sunrpc call_site=get_filesystem refcnt=1 > >> <...>-1027 [000] 13.848692: module_put: sunrpc call_site=put_filesystem refcnt=0 > >> ... > >> modprobe-2587 [001] 1088.437213: module_load: trace_events_sample F > >> modprobe-2587 [001] 1088.437786: module_put: trace_events_sample call_site=sys_init_module refcnt=0 > >> > >> > >> Note: > >> > >> - the taints flag can be 'F', 'C' and/or 'P' if mod->taints != 0 > >> > >> - the module refcnt is percpu, so it can be negative in a specific cpu > >> > >> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> > > > > > > Nice. > > > > Just two worries about it. > > > > The ring buffer are flushed on module unloading right? > > That won't make it easy to perform module event tracing. > > > > Yes, but only when the module has "_ftrace_events" section. > They are ext4 and gfs2 for the current kernel.
Ah, good point.
> > Also the events selftests do a lot of random things to trigger > > each kind of events, I guess some new others will be needed to > > tests these, unless they will seem to fail on every selftests. > > Although I can't imagine a module loading/unloading for > > every ftrace event selftest... I guess these will require > > a specific treatement and also will need to be selftested once > > the filesystem is set to be able to load modules. > > > > It's nice to have more selftests but I don't think it is a > necessity. > > Actually the events selftests just confirm the events won't > crash the system, and no trace entries are generated by them > in the selftests.
Indeed, forget about these worries :)
Thanks.
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