[Valgrind-users] why number of cache miss do not decrease after optimize in ubuntu 12 in VMware player 12?

[Mandy M. <te...@ho...>]

Hi ,


/*
gcc -o marti marti.c
valgrind --tool=cachegrind ./marti
valgrind --dsymutil=yes --tool=callgrind ./marti
*/
int main()
{
 int x[5000][100];
 int i = 0;
 int j = 0;
 for(i = 0; i <5000; ++i)
 {
   for (j = 0; j < 100; ++j)
   {
    x[i][j] = 2*x[i][j];
   }
 }
 return 0;
}
/*
Ubuntu 12 in VMware player 12

 for (j = 0; j < 100; ++j)
 {
 for(i = 0; i <5000; ++i)
   {
    x[i][j] = 2*x[i][j];
   }
 }

==4526== Cachegrind, a cache and branch-prediction profiler
==4526== Copyright (C) 2002-2011, and GNU GPL'd, by Nicholas Nethercote et al.
==4526== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==4526== Command: ./marti
==4526==
--4526-- warning: L3 cache found, using its data for the LL simulation.
==4526==
==4526== I   refs:      6,113,976
==4526== I1  misses:          687
==4526== LLi misses:          682
==4526== I1  miss rate:      0.01%
==4526== LLi miss rate:      0.01%
==4526==
==4526== D   refs:      4,053,131  (3,537,745 rd   + 515,386 wr)
==4526== D1  misses:      501,148  (  500,988 rd   +     160 wr)
==4526== LLd misses:       32,197  (   32,062 rd   +     135 wr)
==4526== D1  miss rate:      12.3% (     14.1%     +     0.0%  )
==4526== LLd miss rate:       0.7% (      0.9%     +     0.0%  )
==4526==
==4526== LL refs:         501,835  (  501,675 rd   +     160 wr)
==4526== LL misses:        32,879  (   32,744 rd   +     135 wr)
==4526== LL miss rate:        0.3% (      0.3%     +     0.0%  )

 for(i = 0; i <5000; ++i)
 {
   for (j = 0; j < 100; ++j)
   {
    x[i][j] = 2*x[i][j];
   }
 }
==4539== Cachegrind, a cache and branch-prediction profiler
==4539== Copyright (C) 2002-2011, and GNU GPL'd, by Nicholas Nethercote et al.
==4539== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==4539== Command: ./marti
==4539==
--4539-- warning: L3 cache found, using its data for the LL simulation.
==4539==
==4539== I   refs:      6,148,278
==4539== I1  misses:          687
==4539== LLi misses:          682
==4539== I1  miss rate:      0.01%
==4539== LLi miss rate:      0.01%
==4539==
==4539== D   refs:      4,072,731  (3,552,445 rd   + 520,286 wr)
==4539== D1  misses:       32,387  (   32,238 rd   +     149 wr)
==4539== LLd misses:       32,197  (   32,062 rd   +     135 wr)
==4539== D1  miss rate:       0.7% (      0.9%     +     0.0%  )
==4539== LLd miss rate:       0.7% (      0.9%     +     0.0%  )
==4539==
==4539== LL refs:          33,074  (   32,925 rd   +     149 wr)
==4539== LL misses:        32,879  (   32,744 rd   +     135 wr)
==4539== LL miss rate:        0.3% (      0.3%     +     0.0%  )
*/



Regards,


Martin