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Date:      Wed, 28 Jan 2004 12:20:46 -0500
From:      Don Bowman <don@sandvine.com>
To:        "'freebsd-current@freebsd.org'" <freebsd-current@freebsd.org>
Subject:   system call performance 4.x vs 5.x [and UP vs MP]
Message-ID:  <FE045D4D9F7AED4CBFF1B3B813C85337035E46FF@mail.sandvine.com>
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This is a very simplistic benchmark, so don't get too hung up on the
accuracy.

If you run this on a given machine on 4.x vs 5.x, you will notice
a dramatic difference [yes, invariants, et al are disabled].

For example, on a 2.0GHz P4-Xeon, HTT enabled, MP kernel, i can
do ~1M socket/s calls on 4.7, but only ~250K/s on 5.2.

     syscall      4.7        5.2
       write  1015036     169800 
      socket  1078994     223253
      select   430564     155077
gettimeofday   252762     183620

As a side note, any idea why gettimeofday is so much more
expensive than socket?

Any suggestion on why such a difference between 4.x and 5.x?
code is compiled the same on each, 'gcc -O2', no threading
options chosen.

For interest, you can try the same program on 4.x in UP vs MP,
and the difference is very dramatic too.

#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <stdio.h>

#define M(n) measure(#n, n);

static void
measure(char *name, void (*fp)(int,...))
{
    double speed;
    int j;
    unsigned long long i = 0;
    unsigned long long us;
    struct timeval tp,tp1;
    gettimeofday(&tp, 0);
    tp1 = tp;

    while (tp1.tv_sec - tp.tv_sec < 10)
    {
        for (j = 0; j < 1000000; j++)
        {
            fp(0,0,0,0);
            i++;
        }
        gettimeofday(&tp1, 0);
    }
    us = ((tp1.tv_sec - tp.tv_sec) * 1000000) + (tp1.tv_usec - tp.tv_usec);
    speed = (1000000.0 * i) / us;
    printf("{%s: %llu %llu %6.2f}\n", name, i,us, speed);
}

static void
doGettimeofday()
{
    double speed;
    unsigned long long i = 0;
    unsigned long long us;
    struct timeval tp,tp1;
    gettimeofday(&tp, 0);
    tp1 = tp;

    while (tp1.tv_sec - tp.tv_sec < 10)
    {
        gettimeofday(&tp1, 0);
        i++;
    }
    us = ((tp1.tv_sec - tp.tv_sec) * 1000000) + (tp1.tv_usec - tp.tv_usec);
    speed = (1000000.0 * i) / us;
    printf("{gettimeofday: %llu %llu %6.2f}\n", i,us, speed);
}

int
main(int argc, char **argv)
{
    M(write);
    M(socket);
    M(select);
    doGettimeofday();
    return 0;
}

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