hello all,
On my Intel Pentium 4 with linux-2.6.23-rc8-rt1, I am getting :
Interrupt Latency result
------------------------
MAX latency : 12.570 micro-seconds
MIN latency : 3.352 micro-seconds
AVG latency : 4.190 micro-seconds
Total Samples : 32583
Please review this interrupt latency module and give your feedback.
Thank you,
Jaswinder Singh.
/*
* Interrupt latency test module
*
* (C) 2007 Jaswinder Singh <jaswinderlinuxrt@xxxxxxxxx>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence Version
* 2 as published by the Free Software Foundation.
*
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bcd.h>
#include <asm/time.h>
//#define DBG_IRQ_LAT /* debug interrupt latency test */
#define TEST_COUNT 20000 /* loop to get max timer count */
/* getting global time from 8254 */
#define READ_CNT0(var) do {var = inb(0x40); var |= (inb(0x40) << 8);} while (0)
#ifdef DBG_IRQ_LAT
#define TEST_CNT 50
static long lat_val[TEST_CNT];
#endif
static volatile long count_c0;
static long max_c0 = 0;
static long cnt_c0 = 0;
static long lat_max = 0;
static long lat_min = 100000000;
static unsigned long irq_cnt = 0;
static unsigned long lat_avg = 0;
static void irq_lat_hdr(void)
{
READ_CNT0(count_c0);
count_c0 = (max_c0 - count_c0);
if (count_c0 > lat_max)
lat_max = count_c0;
if (count_c0 < lat_min)
lat_min = count_c0;
lat_avg = lat_avg + count_c0;
#ifdef DBG_IRQ_LAT
if (irq_cnt < TEST_CNT)
{
lat_val[irq_cnt] = count_c0;
}
#endif
irq_cnt++;
}
/* get maximum timer count */
static long get_max_ticks(void)
{
unsigned long max_ticks = 0;
while(cnt_c0 < TEST_COUNT)
{
READ_CNT0(count_c0);
if (count_c0 > max_ticks)
max_ticks = count_c0;
cnt_c0++;
}
#ifdef DBG_IRQ_LAT
printk("max %lu cnt %lu\n", max_ticks, cnt_c0);
#endif
return max_ticks;
}
static int __init irq_lat_init(void)
{
printk("*************************************\n");
printk("* Interrupt Latency module loaded *\n");
printk("* When you remove this module you *\n");
printk("* will get interrupt latency result *\n");
printk("*************************************\n");
max_c0 = get_max_ticks();
irq_lat_ptr = irq_lat_hdr; /* Install interrupt handler */
return 0;
}
static void __exit irq_lat_exit(void)
{
unsigned long nanosecs = 1000000000;
irq_lat_ptr = NULL; /* Uninstall interrupt handler */
nanosecs = (nanosecs/CLOCK_TICK_RATE);
lat_avg = lat_avg/irq_cnt;
printk("Interrupt Latency result\n");
printk("------------------------\n");
#ifdef DBG_IRQ_LAT
for (count_c0 = 0; count_c0 < TEST_CNT; count_c0++)
printk("%lu: %lu\n", count_c0, lat_val[count_c0]);
printk("CLOCK_TICK_RATE: %d TICK: %lu\n", CLOCK_TICK_RATE, nanosecs);
printk("MAX latency : %lu ticks\n", lat_max);
printk("MIN latency : %lu ticks\n", lat_min);
printk("AVG latency : %lu ticks\n", lat_avg);
#endif
printk("MAX latency : %lu.%03lu micro-seconds\n", (nanosecs * lat_max)/1000, (nanosecs * lat_max) % 1000);
printk("MIN latency : %lu.%03lu micro-seconds\n", (nanosecs * lat_min)/1000, (nanosecs * lat_min) % 1000);
printk("AVG latency : %lu.%03lu micro-seconds\n", (nanosecs * lat_avg)/1000, (nanosecs * lat_avg) % 1000);
printk("Total Samples : %lu\n", irq_cnt);
}
module_init(irq_lat_init);
module_exit(irq_lat_exit);
MODULE_LICENSE("GPL");
obj-name := irq_latency
obj-m := $(obj-name).o
KDIR := $(HOME)/linux-$(shell uname -r)
PWD := $(shell pwd)
default:
$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules
clean:
rm -rf *.ko *.o *.mod.c .*.cmd Mod* .tmp_versions
diff -urN linux-2.6.23-rc8-rt1_org/arch/i386/kernel/time.c linux-2.6.23-rc8-rt1/arch/i386/kernel/time.c
--- linux-2.6.23-rc8-rt1_org/arch/i386/kernel/time.c 2007-10-20 11:24:17.000000000 +0530
+++ linux-2.6.23-rc8-rt1/arch/i386/kernel/time.c 2007-10-20 11:30:31.000000000 +0530
@@ -150,6 +150,10 @@
}
EXPORT_SYMBOL(profile_pc);
+/* Interrupt latency pointer */
+irqlatptr irq_lat_ptr = NULL;
+EXPORT_SYMBOL(irq_lat_ptr);
+
/*
* This is the same as the above, except we _also_ save the current
* Time Stamp Counter value at the time of the timer interrupt, so that
@@ -173,6 +177,10 @@
}
#endif
+ /* Interrupt latency pointer */
+ if (irq_lat_ptr)
+ irq_lat_ptr();
+
do_timer_interrupt_hook();
if (MCA_bus) {
diff -urN linux-2.6.23-rc8-rt1_org/include/asm-i386/time.h linux-2.6.23-rc8-rt1/include/asm-i386/time.h
--- linux-2.6.23-rc8-rt1_org/include/asm-i386/time.h 2007-10-20 11:24:46.000000000 +0530
+++ linux-2.6.23-rc8-rt1/include/asm-i386/time.h 2007-10-20 11:27:35.000000000 +0530
@@ -4,6 +4,10 @@
#include <linux/efi.h>
#include "mach_time.h"
+/* interrupt latency pointer */
+typedef void (*irqlatptr)(void);
+extern irqlatptr irq_lat_ptr;
+
static fastcall inline unsigned long native_get_wallclock(void)
{
unsigned long retval;
