Date: Sat, 25 Mar 2000 18:23:01 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Alfred Perlstein <bright@wintelcom.net> Cc: freebsd-current@FreeBSD.ORG Subject: SMP syscall timing program (was Re: Why are all accesses to the cpl surrounded by a lock?) Message-ID: <200003260223.SAA26218@apollo.backplane.com> References: <200003250527.VAA19096@apollo.backplane.com> <20000325130447.I21029@fw.wintelcom.net>
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:Otherwise right now your guess is as good as mine.
:
:As a side note, it seems silly that we do this:
:
: MPLOCKED incl _cnt+V_SYSCALL
: SYSCALL_LOCK
: call _syscall
:
:I think per-cpu statistics would be an interesting optimization,
:since you're testing all of this, have you been able to measure
:the getuid() loop with and without this (MPLOCKED incl _cnt+V_SYSCALL),
:especially with 2 processes doing a getuid() loop?
:
:--
:-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
Well, in my patch SYSCALL_LOCK is no longer called there so
we can't move the incl and remove the MPLOCKED prefix. A competing
locked instruction costs around 200 nS. I.E. it's expensive, which
is why zone locks aren't a good idea and structural locks are.
I've enclosed my syscall timing program. I will also put it on
my site.
-Matt
Matthew Dillon
<dillon@backplane.com>
/*
* SMPTIME.C
*
* cc smptime.c -o smptime -Wall -DOP=OPn
* ./smptime NFORK
*
* e.g.
*
* cc smptime.c -o smptime -Wall -DOP=OP3
* ./smptime 1
* ./smptime 2
*/
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
#include <setjmp.h>
void deltatime(struct timeval *tv1);
void FigureOutUseCount(void);
#define OP1 sigprocmask(SIG_BLOCK, &sset, &oset);
#define OP2 getpid()
#define OP3 getuid() /* CLEAN OF MP LOCK */
#define OP4 __asm __volatile("addl $1,(%0)"::"r"(global_tmp):"memory")
#define OP5 __asm __volatile("lock; addl $1,(%0)"::"r"(global_tmp):"memory")
#define OP6
#ifndef OP
#error "Missing -DOP=OPn option to cc"
#endif
#define OPNAME(V) #V
int *global_tmp;
int UseCount = 1;
int
main(int ac, char **av)
{
int i;
int count = 0;
int nproc = 2;
sigset_t sset;
sigset_t oset;
struct timeval tv1;
if (ac == 2)
nproc = strtol(av[1], NULL, 0);
sigemptyset(&sset);
sigemptyset(&oset);
gettimeofday(&tv1, NULL);
global_tmp = mmap(NULL, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANON, -1, 0);
FigureOutUseCount();
for (i = 1; i < nproc; ++i) {
if (fork() == 0) {
/*
* child
*/
for (;;) {
OP;
}
_exit(0);
}
}
/*
* parent
*/
for (;;) {
OP;
if (++count == UseCount) {
deltatime(&tv1);
count = 0;
}
}
return(0);
}
void
deltatime(struct timeval *tv1)
{
struct timeval tv2;
int usec;
gettimeofday(&tv2, NULL);
usec = tv2.tv_usec + 1000000 - tv1->tv_usec + 1000000 * (tv2.tv_sec - tv1->tv_sec - 1);
*tv1 = tv2;
printf("%d nsec/call\n", usec / (UseCount / 1000));
}
/*
* Time one second's worth of loops to get a baseline.
*/
jmp_buf TimeEnv;
void
sigAlrm(int sigNo)
{
longjmp(TimeEnv, 1);
}
void
FigureOutUseCount(void)
{
struct itimerval it;
bzero(&it, sizeof(it));
it.it_value.tv_sec = 1;
signal(SIGALRM, sigAlrm);
setitimer(ITIMER_REAL, &it, NULL);
if (setjmp(TimeEnv) == 0) {
for (;;) {
OP;
++UseCount;
}
/* NOT REACHED */
}
signal(SIGALRM, SIG_IGN);
}
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