Hi,
To 1.) doing memset() on the buffers makes a change ... Now the performance is as bad as with mlockall() :( Which means the Linux VM without mlockall makes somehow an optimization for uninitialized heap buffers. Actually nothing to blame on Xenomai here. The reason I was looking at the memcpy native performance was because I found Xenomai Posix message queues somewhat slow: In two tasks where one is receiving a 32 kBytes msg and the other sending to this task 32 kbytes of data, I have an average cycle time of more than 1 ms. Looking at the memcpy performance of my system tells me something: Memcpy(32 KB) -> 400 us Two msg_send(32KB) cannot be less than 2x400 us + 2 ctx switch away, probably even more because we have to write first to Kernel memory, then the ctx switch, then copying from Kernel memory to user buffer, than ctx switch. This simply means I cannot use msg queues for anything bigger than 1K, which means I have to use shared memory for that. As you proposed in another mail maybe it makes a difference to use an own memcpy implementation for ppc which does no read on write. To 2.) I don't have a recent glibc, so that is no option. I can wait however for the new clock_gettime() of Xenomai and use in between the rt_timer_tsc function. Best regards, Daniel Schnell. -----Original Message----- From: Fillod Stephane [mailto:[EMAIL PROTECTED] Sent: 15. maí 2007 15:59 To: Daniel Schnell Cc: [email protected] Subject: RE: [Xenomai-help] memcpy performance on Xenomai That's puzzling. Can it be explained? Have you tried a memset of buf1&buf2 before the first osa_now_timespec? >2.) rt_timer_tsc >If I use clock_gettime() this needs 3100 ns, If I use rt_timer_tsc() >this needs 74 (!) ns. Have you tried clock_gettime with *_HR clock like CLOCK_MONOTONIC_HR ? You have to have a recent glibc to get benefit from that. One of those clock rely on timebase tsc instead of issuing an expensive syscall. Regards, -- Stephane _______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
