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SubjectRe: Threading...
Brian McGrew wrote:
> On 1/19/07 10:55 AM, "Arjan van de Ven" <> 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 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 <>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
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