[Qemu-devel] tests with simulated memory

[Johan Rydberg]

Hi,

I've hacked a bit on QEMU and added simulated memory using a 
translation cache as we discussed earlier.  These tests are 
mostly for my own interest, but you might find them interesting
aswell.

Below is the result of the BYTEmark [1] benchmark (I do not have 
access to any of the SPEC benchmarks) using simulated memory:

NUMERIC SORT:  Iterations/sec.: 10.385957       Index: 0.268406 
STRING SORT:   Iterations/sec.: 1.807970        Index: 0.794712
BITFIELD:      Iterations/sec.: 1913364.293577  Index: 0.328203
FP EMULATION:  Iterations/sec.: 0.647669        Index: 0.311379
FOURIER:       Iterations/sec.: 619.696756      Index: 0.701681
ASSIGNMENT:    Iterations/sec.: 0.151103        Index: 0.575697
IDEA:          Iterations/sec.: 21.734410       Index: 0.332534
HUFFMAN:       Iterations/sec.: 13.068599       Index: 0.363168

Same test without the simulated memory (original QEMU):

NUMERIC SORT:  Iterations/sec.: 20.327522       Index: 0.525327
STRING SORT:   Iterations/sec.: 2.919430        Index: 1.283266
BITFIELD:      Iterations/sec.: 3086647.786244  Index: 0.529458
FP EMULATION:  Iterations/sec.: 1.112348        Index: 0.534783
FOURIER:       Iterations/sec.: 717.791439      Index: 0.812754
ASSIGNMENT:    Iterations/sec.: 0.208943        Index: 0.796063
IDEA:          Iterations/sec.: 39.651108       Index: 0.606657
HUFFMAN:       Iterations/sec.: 19.098677       Index: 0.530740

Slowdown rates (calculated using the Index field from original 
QEMU divided with the Index from the QEMU w/ simulated memory):

NUMERIC SORT:  1.96
STRING SORT:   1.61
BITFIELD:      1.61
FP EMULATION:  1.72
FOURIER:       1.16
ASSIGNMENT:    1.38
IDEA:          1.82
HUFFMAN:       1.46

The slowdown would be greater if any processing must have been
done on every cache miss.  The current hack just adds the page
to the cache and does the memory transaction and returns.

A slowdown between 1.16x and ~2x is pretty good I think.

As reference, below is the results for Valgrind (CVS version,
running the none skin):

NUMERIC SORT:  Iterations/sec.: 36.541455       Index: 0.944346
STRING SORT:   Iterations/sec.: 2.181686        Index: 0.958983
BITFIELD:      Iterations/sec.: 6294984.678336  Index: 1.079789
FP EMULATION:  Iterations/sec.: 2.232148        Index: 1.073148
FOURIER:       Iterations/sec.: 746.055296      Index: 0.844757
ASSIGNMENT:    Iterations/sec.: 0.386720        Index: 1.473388
IDEA:          Iterations/sec.: 80.463770       Index: 1.231086
HUFFMAN:       Iterations/sec.: 43.592067       Index: 1.211396

 [1] http://www.byte.com/bmark/bmark.htm

best regards,
johan

-- 
Johan Rydberg, Free Software Developer, Sweden
http://rtmk.sf.net | http://www.nongnu.org/guss/

Playing Track No09