The process portion is extremely short : removing the head element of a
queue then putting it at the tail of the queue, this is done 10 times. This
does not make sense, but this is done just for test purpose.
----- Original Message -----
From: "Calin A. Culianu" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, September 27, 2001 5:40 PM
Subject: Re: [rtl] SMP mutex/scheduling problem ?
>
> That's weird... How long does the process portion alone take?
>
> On Tue, 25 Sep 2001, lionel wrote:
>
> > The context :
> > We are designing a realtime Radio Link Control driver with hard real
time
> > constraints.
> >
> >
> > We launch 2 threads on a bi processor, 1 thread on P1, 1 thread on P2.
> > Both threads run in an infinite loop and both are periodic (10 milli
> > seconds).
> > Both treads try to lock a mutex, make a few code then unlock the mutex
(they
> > try to access a shared list protected by a mutex).
> > The execution time of the code between the lock and the unlock of the
mutex
> > is no more than a few micro seconds.
> >
> > But when I mesure the execution time of the code that lock, process, and
> > then unlock the mutex with the help of the function clock_gethrtime(), I
can
> > notice than sometimes it take 5 milli seconds (the value is nearly
always
> > the same : 5ms +/- a few micro seconds) ???.
> >
> > Any help would be appreciated.
> >
> > Thanks.
> >
> > -----------------------------------------------------
> > Hardware : Bi processor PIII 1 GHz 512Mo
> > -----------------------------------------------------
> > Software :
> > Redhat 7.1
> > Kernel 2.4.4 from kernel.org
> > RT-Linux 3.1
> > -----------------------------------------------------
> > Code for thread 1 (idem for thread 2 except counter2):
> >
> > void *thread_test1(void* notusedP) {
> >
> > hrtime_t start, end, process;
> > pthread_make_periodic_np(pthread_self(), gethrtime(), 10000000); /*
10
> > milli seconds */
> >
> > while (1) {
> >
> > start = gethrtime();
> >
> > /* code that acquire a mutex here not detailled */
> >
> > end = gethrtime();
> > process = end - start;
> > if (process > 1000000) { /* 1 milli second */
> > counter1+=1; // extern variable displayed when cleaning up the
module
> > }
> > pthread_wait_np();
> > }
> > }
> >
> >
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> >
>
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