Dan Eischen and Julian Elischer,I'd really like the ability to "pin" to a processor. However, I think I need something stronger than immediately rescheduling the current process as seems to be done in the 4bsd scheduler. I'd like to "own" the cpu as much as possible until the "pinned" thread yields it or terminates.
I've run some user-space and kernel-space tests in FreeBSD 6.2 with preemption turned off that look as follows:
I created a pthread with both libpthread and libthr that had PTHREAD_SCOPE_SYSTEM set with pthread_attr_setscope. The thread then calls a system call module I created that calls sched_bind and sched_pin on the thread.
The same is true for the kernel, only I create a thread in the kernel with kthread_create and then bind and pin it.
the bound thread in both cases iterates 10,000,000 times, and for each iteration
1) takes a timestamp with rdtsc() (x86) 2) spins until the delta from that timestamp is >= 100 3) classifies the delta as short or long, short is a delta <= 400 4) repeat Short trials are on average 102 cycles (good) Long trials are on average 950-1100 cycles (bad) There are 950-1100 long trials for every 10,000,000 trial run. This means I'm getting an abnormal trial 1300-1550 times a secondWhile this is not the end of the world, it is causing me difficulties with my experiments as I'm trying to process 1,488,095 Ethernet frames per second, meaning a new 64B frame is ready every 672ns. These abnormalities are causing me to require queuing and reduce the maximum processing time to account for it, which is less than ideal :)
Right now I have a setup that lets me stream 100% of frames from an input handler thread in the kernel to a user-space thread and back to an output handler kernel thread for all frames >=96B, and 95% of the frames for 64B (I can't seem to generate more than that on my hardware).
Therefore it looks like I need to find a way to eliminate all non- application requested tasks including the periodic scheduler and any callout code.
Do either of you have any thoughts or ideas? I'm attaching the test code I used to generate these numbers. Thanks in advance for any help! John Giacomoni
pintest.tgz
Description: Binary data
On Feb 9, 2007, at 9:53 PM, Daniel Eischen wrote:
On Fri, 9 Feb 2007, Julian Elischer wrote:Peter Holmes wrote:This is something I am interested in doing as well. I had corresponded with Julian Eischen & Daniel Elischer about this.Dan Eischen and Julian Elischer :-)Yes, it needed byte reversal or something. That would indeed be a strange union! I think it would be nice to have something like Solaris pbind(1) and processor_bind(2). -- DE _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackersTo unsubscribe, send any mail to "freebsd-hackers- [EMAIL PROTECTED]"
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