On Sat, Apr 23, 2011 at 10:40 AM, Stefan Hajnoczi <[email protected]> wrote: > On Fri, Apr 22, 2011 at 12:46 PM, Francis Moreau <[email protected]> > wrote: >> On Fri, Apr 22, 2011 at 7:29 AM, Francis Moreau <[email protected]> >> wrote: >>> 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. >> >> >> Thinking more about it, I think that both solution (probe or >> tracepoint) are not adapted. >> >> Because I'm interested in discovering the path taken by the kernel >> from a given syscall, therefore I don't know this path. However both >> solution imply that the path is known since you need to insert some >> 'probes' in this path to see it... > > You can use "Dynamic ftrace with the function graph tracer" > (set_graph_function): > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/trace/ftrace.txt;hb=HEAD#l1664 > > I don't know of way to do this using perf(1).
I don't know either but since perf interface is more convenient than sysfs one, I was wondering if that was possible with 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
