interrupt duration
Andrew Maximov
amaximus at mail.ru
Fri May 11 17:51:24 UTC 2001
----- Original Message -----
From: "Joel Sherrill" <joel.sherrill at OARcorp.com>
To: "Andrew Maximov" <amaximus at mail.ru>
Cc: "RTEMS User List" <rtems-users at oarcorp.com>
Sent: Friday, May 11, 2001 4:36 PM
Subject: Re: interrupt duration
My configuration:
CPU: Pentium MMX - 125 Mhz
MEMORY: 32M
VIDEO: S3TrioV+
I write simple test. First I change _ISR_Handler in irq_asm.S for for
interrupt duration measurement.
here is a fragment from _ISR_Handler ( full source code attached )
SYM (_ISR_Handler):
...
.check_stack_switch:
pushl ebp
movl esp, ebp # ebp = previous stack pointer
cmpl $0, SYM (_ISR_Nest_level) # is this the outermost
interrupt?
jne nested # No, then continue
movl SYM (_CPU_Interrupt_stack_high), esp
/*
* We want to insure that the old stack pointer is on the
* stack we will be on at the end of the ISR when we restore it.
* By saving it on every interrupt, all we have to do is pop it
* near the end of every interrupt.
*/
nested:
incl SYM (_ISR_Nest_level) # one nest level deeper
incl SYM (_Thread_Dispatch_disable_level) # disable
multitasking
/*
* re-enable interrupts at processor level as the current
* interrupt source is now masked via i8259
*/
rdtsc # this is
my patch EDX:EAX - number of CPU cycles since power up
mov eax,SYM (old_rdtsc) (,ecx,4) # this is my patch save
ticks
sti
/*
* ECX is preloaded with the vector number but it is a scratch register
* so we must save it again.
*/
pushl ecx # push vector number
mov SYM (current_irq) (,ecx,4),eax
# eax = Users handler
call *eax # invoke user ISR
/*
* disable interrupts_again
*/
cli
popl ecx # ecx = vector number
rdtsc # this is
my patch
sub SYM (old_rdtsc) (,ecx,4), eax # this is my patch
cmp eax, SYM (max_rdtsc) (,ecx,4) # this is my patch
jnb .dont_update_max_rdtsc # this is my patch
mov eax, SYM (max_rdtsc) (,ecx,4) # this is my patch (store
maximum of interrupt duration)
.dont_update_max_rdtsc:
/*
* restore stack
*/
movl ebp, esp
popl ebp
...
BEGIN_DATA # this is my patch
SYM(old_rdtsc): # this is my patch
.rept 16 # this is my
patch
.long 0 # this is my
patch
.endr # this is my
patch
PUBLIC (max_rdtsc) # this is my patch
SYM(max_rdtsc): # this is my patch
.rept 16 # this is my
patch
.long 0 # this is my
patch
.endr # this is my
patch
END_DATA # this is my patch
and here is a C fragment
#define CONFIGURE_INIT
#include <rtems.h>
rtems_task Init( rtems_task_argument argument );
/* configuration information */
#include <bsp.h>
#define CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER
#define CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER
#define CONFIGURE_MAXIMUM_TASKS 32
#define CONFIGURE_MAXIMUM_TIMERS 32
#define CONFIGURE_RTEMS_INIT_TASKS_TABLE
#define CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM
#include <confdefs.h>
#include <stdio.h>
rtems_id statistics_timer;
extern unsigned int max_rdtsc[];
rtems_timer_service_routine
statistics_fire_proc( rtems_id timer_id, void *unused )
{
int i;
for ( i=0; i<16; i++ ) {
if ( (i&7) == 0 ) printf("\n");
printf("t%d:%u ",i,max_rdtsc[i]);
max_rdtsc[i] = 0;
}
printf("\n");
rtems_timer_reset( timer_id );
}
rtems_task Init(
rtems_task_argument ignored
)
{
rtems_status_code status;
rtems_name name;
rtems_interval ticks_per_second;
rtems_clock_get( RTEMS_CLOCK_GET_TICKS_PER_SECOND, &ticks_per_second );
name = rtems_build_name( 'T', 'E', 'S', 'T' );
status = rtems_timer_create( name, &statistics_timer );
if ( status != RTEMS_SUCCESSFUL ) rtems_fatal_error_occurred(status);
status = rtems_timer_fire_after( statistics_timer,
ticks_per_second,
statistics_fire_proc,
NULL);
if ( status != RTEMS_SUCCESSFUL ) rtems_fatal_error_occurred(status);
printf( "\n\ninterrupt measurement start.\n" );
rtems_task_suspend( RTEMS_SELF );
}
1. After start, IRQ0 - 52313 ( 417 microseconds on my PC )
2. After 20-30 seconds, IRQ0 - 3250835 ticks ( 26 ms !!! on my PC )
What I do wrong ?
> Andrew Maximov wrote:
> >
> > RTEMS: rtems-4.5.0
> > BSP: pc586
> >
> > I have a question about interrupt duration.
> > I change irq_asm.S for interrupt duration measurement.
> > This is a result of interrupt duration measurement.
> >
> > IRQ0 - 4596784 ticks ( rdtsc intstruction )
> > IRQ1 - 0
> > ...
> > IRQ10 - 8321/4601374 ( this is my device )
> > ...
> > IRQ15 - 0
> >
> > By default all IRQs has equal priority, therefore
> > IRQ10 can be interrupted by IRQ0. And process time of
> > IRQ10 is increasing.
> > I solved this problem by increasing priority of IRQ10.
> > But why IRQ0 has such long process time ?
> > IRQ0 handler call rtems_clock_tick().
>
> First doesn't rdtsc read the number of CPU cycles
> since power up? That means that 8321 is only
> about 8.3 microseconds for a 100 Mhz part or
> 2.1 for a 400 Mhz part.
>
> On the i386, interrupts do not nest unless the handlers
> make special provisions to lower interrupts. If you
> think you are measuring nested interrupts, then
> my suspicion is that your start/end time marks are
> not matched like you think.
>
> rtems_clock_tick() has a O(n) in it based upon the number
> of time events that fire at the same clock tick. For example,
> if the delay for 10 tasks ends on the same clock tick, there
> will be 10 unblocking operations. But I doubt this is
> what you are seeing.
>
>
------------------------------------------------------------------------
> > Name: irq_asm.S
> > irq_asm.S Type: unspecified type (application/octet-stream)
> > Encoding: quoted-printable
>
> --
> Joel Sherrill, Ph.D. Director of Research & Development
> joel at OARcorp.com On-Line Applications Research
> Ask me about RTEMS: a free RTOS Huntsville AL 35805
> Support Available (256) 722-9985
>
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