[ltt-dev] (forw) [chris.meyers.fsu@gmail.com: Re: ltt channel thread safe?]

[compudj@krystal.dyndns.org (Mathieu Desnoyers)]

* Fu Juntang(David) (juntang.fu at windriver.com) wrote:
> Hi,Mathieu:
>   Please see my answer inline:
> 
> On Thu, 2010-08-12 at 09:40 -0400, Mathieu Desnoyers wrote:
> > * Fu Juntang(David) (juntang.fu at windriver.com) wrote:
> > > Hi,Mathieu:
> > >   I have found another UST bug in this multi-thread functions:
> > >   in my SMP host(2 cpu cores),I have found that UST can only collect one
> > >  thread trace logs running one core(CPU_1),but can not collect the 
> > >  other thread trace logs running another core(CPU_0),is this a known
> > > bug?
> > >   if you need my debug logs, I can attach it to you. 
> > 
[...]
> > Can you try putting a printf in 
> > 
> > ust/libust/buffer.c: get_n_cpus() to see how many CPUs the library
> > detects ?
> > 
> yes,sure, the output says that it detects 2 cpus
> 
> > What does your usttrace directory looks like ? (the subdir containing
> > the ust and metadata files... with ls -al)
> > 
> total 24
> drwxr-xr-x 2 david david 4096 2010-08-13 15:30 .
> drwxr-xr-x 3 david david 4096 2010-08-13 15:30 ..
> -rw------- 1 david david 4096 2010-08-13 15:30 metadata_0
> -rw------- 1 david david 4096 2010-08-13 15:30 metadata_1
> -rw------- 1 david david 4096 2010-08-13 15:30 ust_0
> -rw------- 1 david david 4096 2010-08-13 15:30 ust_1
> 

It all looks fine so far. Note that the Linux scheduler can decide to
schedule your 2 threads on the same CPU. How do you detect that there is
a "problem": is it that events you are writing from a specific thread
are missing or that you expect events on CPU 1 and don't have any ?

The latter case could be normal.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com