Re: how to get a kernel callgraph starting from a syscall

[David Ahern <dsahern@xxxxxxxxx>]

On 04/21/11 12:48, Francis Moreau wrote:
> On Thu, Apr 21, 2011 at 5:23 PM, David Ahern <dsahern@xxxxxxxxx> wrote:
>>
>>
>> On 04/21/11 01:46, Francis Moreau wrote:
>>> Hello,
>>>
>>> Sorry if the question is dumb but I'm a bit lost about this.
>>>
>>> I know that ftrace exists but I think that perf can do this too: I
>>> have a userspace application which is calling a libc C function (read)
>>> which ends up doing a sys_read.
>>>
>>> For the sys_read, I'd like to see what's happening in the kernel by
>>> displaying the call graph.
>>>
>>> Can perf do that ?
>>
>> Have you tried 'perf record -g'?
>>
> 
> Well, I don't see how it can be done with perf record -g.
> 
> Let's say I'm interested to see the path taken in the kernel when a
> process is calling sys_sleep:
> 
>   $ perf record -g sleep 1
> 
> Then I can use:
> 
>   $ perf report -g
> 
> But I don't see what I am asking for.
> 
> What am I missing ?

You want the individual samples? if so, perf script dumps them and you
can see the callchain for each sys_read.

David

> 
> Thanks
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