On Fri, Apr 22, 2011 at 2:47 AM, David Ahern <[email protected]> wrote: > 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 >
Thanks for you answer. I think I'll use probe. Maybe it would be nice to have ftrace integrated in perf ? Thanks -- Francis -- 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
