Date: Tue, 2 Oct 2007 01:14:20 -0700 (PDT) From: Jeff Roberson <jroberson@chesapeake.net> To: NIIMI Satoshi <sa2c@sa2c.net> Cc: freebsd-current@freebsd.org, freebsd-threads@freebsd.org Subject: Re: sched_yield() is very slow when other threads are busy on FreeBSD-current Message-ID: <20071002011337.Q6669@10.0.0.1> In-Reply-To: <46FD4B09.20006@sa2c.net> References: <46FD4B09.20006@sa2c.net>
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On Sat, 29 Sep 2007, NIIMI Satoshi wrote:
> Hi,
>
> I experienced sched_yield() is very slow when other threads are busy
> on FreeBSD-current.
Hello,
Can you please try the enclosed patch and tell me if it addresses your
problem?
Thanks,
Jeff
>
> When I run the program:
> ------------------------------------------------
> #include <assert.h>
> #include <stdio.h>
> #include <pthread.h>
>
> #define NUM_THREAD (10)
>
> volatile int run = 0;
>
> void *start(void *p)
> {
> while (!run)
> ;
> return p;
> }
>
> int main()
> {
> pthread_t th[NUM_THREAD];
> int i;
> for (i = 0; i < NUM_THREAD; i++) {
> assert(pthread_create(&th[i], NULL, start, NULL) == 0);
> sched_yield();
> }
> run = 1;
> for (i = 0; i < NUM_THREAD; i++)
> assert(pthread_join(th[i], NULL) == 0);
> return 0;
> }
> ------------------------------------------------
> The output of /usr/bin/time:
>
> FreeBSD 6.2-RELEASE, libthr, HZ=100, GENERIC kernel:
> 0.55 real 0.55 user 0.00 sys
>
> FreeBSD 7-CURRENT, libthr, HZ=100, kernel
> include GENERIC
> nooptions INVARIANTS, INVARIANT_SUPPORT, WITNESS, WITNESS_SKIPSPIN:
> 164.16 real 162.80 user 0.00 sys
>
> I tried SCHED_ULE too, but does not help so much.
>
> Increasing HZ helps to perform better, but still very slower than FreeBSD-6.
>
> Thanks,
> --
> NIIMI Satoshi
> _______________________________________________
> freebsd-threads@freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-threads
> To unsubscribe, send any mail to "freebsd-threads-unsubscribe@freebsd.org"
>
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