On 04/21/11 14:07, Francis Moreau wrote: > On Thu, Apr 21, 2011 at 9:49 PM, David Ahern <[email protected]> wrote: >> >> You want the individual samples? if so, perf script dumps them and you >> can see the callchain for each sys_read. >> > > hmm, I don't see what you mean by individual samples. > > I don't think sampling can help in my case (tracing the callchain of > one syscall). > > Could you give me an example of what you have in mind ? > > Thanks
I think I get it now. 'perf record' for syscall event stops at sys_read as that is the point the event is generated. You want where the kernel goes starting with sys_read. In that case you are limited to the pre-existing tracepoints (see 'perf list -e tracepoints') to trigger an event and back trace, or if the read causes the processes to block you can you use the context-switch event or sched_switch trace point. You could also insert probe points using perf probe. Lin Ming posted an example of this a couple of weeks ago: # ./perf probe -k ~/vmlinux -s ~/linux-2.6/ find_get_page # ./perf record -e probe:find_get_page -f -g -a David -- To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
