lkml.org 
[lkml]   [2007]   [Jan]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Threading...
Brian McGrew wrote:
> On 1/19/07 10:55 AM, "Arjan van de Ven" <arjan@infradead.org> wrote:
>> On Fri, 2007-01-19 at 10:43 -0800, Brian McGrew wrote:
>>> I have a very interesting question about something that we're seeing
>>> happening with threading between Fedora Core 3 and Fedora Core 5. Running
>>> on Dell PowerEdge 1800 Hardware with a Xeon processor with hyper-threading
>>> turned on. Both systems are using a 2.6.16.16 kernel (MVP al la special).
>>>
>>> We have a multithreaded application that starts two worker threads. On
>>> Fedora Core 3 both of these we use getpid() to get the PID of the thread and
>>> then use set_afinity to assign each thread to it's own CPU. Both threads
>>> run almost symmetrically even on their given CPU watching the system
>>> monitor.
>> this is odd; even in FC3 getpid() is supposed to return the process ID
>> not the thread ID
>>
>>> What am I missing? What do I need to do in FC5 or the kernel or the
>>> threading library to get my threads to run in symmetric parallel again???
>> you should fix the app to use something like pthread_self() instead...
>> (or the highly unportable gettid() but that would just be horrible)
> -----
>
> And on FC5 I am using pthread_self but my problem isn't simply with
> pthread_self, it's with the scheduling. On FC3 both threads run
> simultaneously in almost symmetric parallel. On FC5 one thread don't pick
> up and start until the previous one is done. On FC3, using getpid for the
> thread I could use set_afinity to force each thread to its own processor and
> with FC5 I can't; so I've got one idle processor all the time.
>
This sounds so unlikely I hesitate to mention it, but you are not, by
any chance, running pthreads on one and nptl on the other, are you?

--
bill davidsen <davidsen@tmr.com>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-01-19 23:09    [from the cache]
©2003-2011 Jasper Spaans