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Re: [Qemu-devel] tests with simulated memory

From: Johan Rydberg
Subject: Re: [Qemu-devel] tests with simulated memory
Date: Thu, 19 Jun 2003 19:31:09 +0200

Fabrice Bellard <address@hidden> wrote:

: Some days ago I looked for a benchmark to publish QEMU objective results 
: (gzip is not enough!). The BYTEmark you mention seems a good start. SPEC 
: benchmarks are less interesting since their source code cannot be easily 
: distributed.

Yes.  And the Linux nbench testsuite is based on BYTEmark.  I used the
sources from byte's website.  Maybe you should try nbench instead.

: I would have expected the slowdown to be more important. In the code you 
: submitted you did not include alignment tests. Hopefully by just anding 
: the address with '0xffff0003' you do both address translation _and_ 
: unaligned access handling...

I was a bit suprised aswell.  It though you would get a slowdown of 
something like 2x - 8x, esp since x86 programs does a lot of memory

Regarding alignment checks. I'm not sure it is needed for the x86 platform 
though, since it supports unaligned memory accesses. (but there is some bit 
that enabled alignment checks, isn't there?)

: It seems that Valgrind is twice as fast on most tests. Some 
: optimisations will be needed in qemu to correct that :-)

Hehe.  I was a bit suprised by the result.  I thought QEMU would perform 
better, esp since it must spend less time decoding and more time executing 
than Valgrind (doing the register allocation + improvements of the micro 
operations isn't cheep).

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

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