On Wed, Aug 22, 2012 at 05:26:47PM +0300, Mitya wrote: > 22.08.2012 17:36, Luigi Rizzo ??????????????: > >On Wed, Aug 22, 2012 at 02:32:21AM +0000, Bruce Evans wrote: > >>luigi wrote: > >> > >>>even more orthogonal: > >>> > >>>I found that copying 8n + (5, 6 or 7) bytes was much much slower than > >>>copying a multiple of 8 bytes. For n=0, 1,2,4,8 bytes are efficient, > >>>other cases are slow (turned into 2 or 3 different writes). > >>> > >>>The netmap code uses a pkt_copy routine that does exactly this > >>>rounding, gaining some 10-20ns per packet for small sizes. > >>I don't believe 10-20ns for just the extra bytes. memcpy() ends up > >>with a movsb to copy the extra bytes. This can be slow, but I don't > >>believe 10-20ns (except on machines running at i486 speeds of course). > >I am adding at the end a test program so people can try things on their hw. > > > >Build it with > > > > cc -O2 -Werror -Wall -Wextra -lpthread -lrt testlock.c -o testlock > > > > > > # uname -a > FreeBSD m18.cabletv.dp.ua 9.0-STABLE FreeBSD 9.0-STABLE #1: Tue Apr 24 > 13:23:05 EEST 2012 r...@m18.cabletv.dp.ua:/usr/src/sys/i386/compile/m18 i386 > > cc -O2 -Werror -Wall -Wextra -lpthread -lrt testlock.c -o testlock > > testlock.c: In function 'test_rdtsc': > testlock.c:151: error: can't find a register in class 'AD_REGS' while > reloading 'asm' > testlock.c:151: error: 'asm' operand has impossible constraints
i forgot to mention that i tried this only on amd64, my ASM is horrible. Just comment out the offending lines and do not run those tests. Or, if you have a portable fix, let me know and everybody will appreciate it. cheers luigi _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
