Date: Thu, 15 Aug 1996 07:13:54 +1000 From: Bruce Evans <bde@zeta.org.au> To: msmith@atrad.adelaide.edu.au, nate@mt.sri.com Cc: freebsd-hackers@freefall.freebsd.org, ponds!rivers@dg-rtp.dg.com, ponds!rivers@freefall.freebsd.org, sag.space.lockheed.com!handy@dg-rtp.dg.com Subject: Re: sio issues (silo overflows on a pentium, locked in ttywait, etc...) Message-ID: <199608142113.HAA04204@godzilla.zeta.org.au>
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>see the overflows affecting me much. The funny thing is I don't see
>overflows on the SLIP server box which is also running 16550A UARTS and
>is running multiple sessions, but it's not running X and never touches
>the hard disk. (Basically it's the same hardware on both boxes, 486/66
>with 16MB, although my box has an Adaptec 1542B and the server box is
>IDE).
Upgrade everything to IDE :-). Some busmastering SCSI controllers hog
the bus for too long (e.g., Ultrastor U34Fs sometimes hog it for 160 us
so they are unusable with single 8250s at speeds > 57600, unusable with
single 16550s at speeds > 115200, and barely usable with single UARTS at
exactly these speeds. The aha driver sets the bus on/off times to 7/4,
so there should be no problems with single UARTs.
Here is my throwaway lkm and auxiliarly program for testing bus hogging.
Usage: make and load the lkm. Run modstat to see what its syscall
number is. It will be 210 if there are no other syscall-lkms. If
the number isn't 210, then change 210 in hogtime.c to the number.
Compile and run the hogtime utility. Start processes to exercise
the bus hog(s), e.g., `dd bs=1024k </dev/rsd0 >/dev/null'. Watch the
output from hogtime.
Bruce
---
lkm/hogtime/Makefile
---
BINDIR= /tmp
SRCS= mycall.c
KMOD= newsyscall_mod
NOMAN= none
CLEANFILES+= ${KMOD}
.include <bsd.kmod.mk>
---
lkm/hogtime/mycall.c
---
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/exec.h>
#include <sys/kernel.h>
#include <sys/sysent.h>
#include <sys/lkm.h>
#define mycall hogtime
static int mycall(struct proc *p, void *uap, int *retval);
static struct sysent newent = { 0, mycall, };
MOD_SYSCALL("newsyscall_mod", -1, &newent);
extern int newsyscall_mod(struct lkm_table *lkmtp, int cmd, int ver);
int newsyscall_mod(struct lkm_table *lkmtp, int cmd, int ver)
{
DISPATCH(lkmtp, cmd, ver, lkm_nullcmd, lkm_nullcmd, lkm_nullcmd)
}
#ifdef MEMTEST
#define ADDR 0xf00d4000
#endif
static int hogtime(struct proc *p, void *uap, int *retval)
{
int i, j, start, finish, delta;
#ifdef MADDR
volatile u_char *maddr;
#endif
long usec;
disable_intr();
for (i = 0; i < 2; ++i) {
/*
* i = 0: load cache, if any. i = 1: calibrate and count.
* Calibration must be combined with counting so that the
* same i/o wait states apply to both.
*/
#ifdef MEMTEST
maddr = (volatile u_char *)ADDR;
#endif
outb(0x43, 0x00);
start = inb(0x40);
start |= inb(0x40) << 8;
#ifndef MEMTEST
inb(0x43); /* 7 dummy i/o's to get 10 altogether */
inb(0x43);
inb(0x43);
inb(0x43);
inb(0x43);
inb(0x43);
inb(0x43);
for (j = 0; j < 100; ++j)
;
#else
for (j = 0; j < 0x100; j += 2)
*(maddr + j);
#endif
outb(0x43, 0x00);
finish = inb(0x40);
finish |= inb(0x40) << 8;
}
enable_intr();
delta = start - finish;
#define TIMER_FREQ 1193182
#define LATCH ((TIMER_FREQ + hz / 2) / hz)
if (delta < 0)
delta += LATCH;
usec = (delta * tick + LATCH / 2) / LATCH;
*retval = usec;
return 0;
}
static long microtime_buf[4096];
static int microtime_test(struct proc *p, void *uap, int *retval)
{
int i;
struct timeval tv;
struct timeval tvp;
microtime(&tvp);
for (i = 0; i < 4096; ++i)
{
microtime(&tv);
microtime_buf[i] = tv.tv_usec - tvp.tv_usec
+ 1000000 * (tv.tv_sec - tvp.tv_sec);
tvp = tv;
}
return 0;
}
---
bin/hogtime.c
---
#include <limits.h>
#include <stdio.h>
#include <unistd.h>
int main(void)
{
for (;;)
{
int i;
long max = 0;
long min = LONG_MAX;
long tot = 0;
int val;
for (i = 0; i < 10000; ++i)
{
val = syscall(210);
if (val == -1)
{
perror("syscall");
exit(1);
}
if (max < val)
max = val;
if (min > val)
min = val;
tot += val;
}
printf("min = %ld, av = %ld, max = %ld\n", min, tot / i, max);
}
return 0;
}
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