Re: 7.52 second kernel compile

[Davide Libenzi]

On Mon, 18 Mar 2002, David S. Miller wrote:

>    From: Cort Dougan <[e-mail]>
>    Date: Mon, 18 Mar 2002 17:36:35 -0700
>
>    The structure of the program you suggested with more portable timing.
>
> Oh, just something like:
>
>
> 	gettimeofday(&stamp1);
> 	for (A MILLION TIMES) {
> 		TLB miss;
> 	}
> 	gettimeofday(&stamp2);

This make the measure stable on my machine :

#define rdtsc(low) \
   __asm__ __volatile__("rdtsc" : "=A" (low) : )

            unsigned long long start, end;

            rdtsc(start);
            access(buffer[i]);
            rdtsc(end);

processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 6
model           : 4
model name      : AMD Athlon(tm) Processor
stepping        : 2
cpu MHz         : 999.561
cache size      : 256 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov
		pat pse36 mmx fxsr syscall mmxext 3dnowext 3dnow
bogomips        : 1992.29

$ gcc -o tlb_test tlb_test.c

#APP
    rdtsc
#NO_APP
    movl    %eax, -24(%ebp)
    movl    %edx, -20(%ebp)
    movl    -4(%ebp), %eax
    addl    -12(%ebp), %eax
    movl    (%eax), %eax
#APP
    rdtsc

  11.89: 18
   4.70: 20
  81.90: 23

$ gcc -O2 -o tlb_test tlb_test.c

#APP
    rdtsc
#NO_APP
    movl    %edx, -28(%ebp)
    movl    -24(%ebp), %edx
    movl    %eax, -32(%ebp)
    movl    (%esi,%edx), %ecx
#APP
    rdtsc
#NO_APP

  87.70: 20
  11.24: 25

- Davide