On Thu, 07 Feb 2008 17:27:53 +0100 Matthieu CASTET <matthieu.castet@xxxxxxxxxx> wrote: > Hi Sébastien, > > Sébastien Dugué wrote: > > Hello Matthieu, > > > > On Thu, 07 Feb 2008 14:49:07 +0100 Matthieu CASTET <matthieu.castet@xxxxxxxxxx> wrote: > > > >> hi, > >> > >> I am trying to use some IBM rt test on arm. > >> > >> > >> I define atomic_add to > >> assert(i==1); > >> return ++(v->counter); > >> > >> That's a bit ugly, but that should work for my need. > > > > That would be the poor man's atomic_inc() and not sure it really does > > what you think it does ;). Just for the record, pre-armv6 cores have no support > > for userland atomic operations (aside from swapping). > I can, if I use a kernel helper :) [1] Yep, but much slower. > > BTW what should do the atomic_add. > On i386 it does the atomic add and return the value in memory before the > add (Exchange and Add). Looking at the kernel and glibc, i386's atomic_add seems to be a void function (unless I missed something). > On powerpc, it seems to do the atomic add and return the new value. Yes, both for kernel and glibc implementations. > > > > > >> But I have a problem with the sched_latency test. > >> On my platform the thread creation is quite slow (25ms), so with the > >> default value, I got a PERIOD MISSED. > > > > The IBM RT tests have been integrated into the LTP and I recently > > sent some updates to those testcases. Notably one the patches did improve > > the thread starting time. Other patches did touch this particular test too. > > > > Could you try the latest release (from LTP) and tell me if things > > have improved for you. > Ok I will try them. > > > > Also, the PASS/FAIL criteria are quite arbitrary. They happen to be fine > > for most recent PC-class hardware but surely not for embedded systems and > > should be tuned according to your RT requirements. > Yes I saw that. > > > > > >> Also my cpu is quite slow (compared to last intel core or powerpc). For > >> example a sched_jitter run take 6s. > > > > Ouch! What's your CPU (core type, clock speed)? > Arm926 ~104.65 Mhz ARMv5 core then. You'll need the kernel helper then to be trully atomic. Sebastien. - To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
