Re: [Qemu-trivial] [Qemu-devel] [PATCH] tcg: optimise memory layout of TCGTemp

[Stefan Weil <sw@weilnetz.de>]

Am 29.03.2015 um 23:52 schrieb Richard Henderson:
> On Mar 27, 2015 14:09, "Emilio G. Cota" <cota@braap.org> wrote:
>> On Fri, Mar 27, 2015 at 09:55:03 +0000, Alex Bennée wrote:
>>> Have you been able to measure any performance improvement with these new
>>> structures? In theory, if aligned with cache lines, performance should
>>> improve but real numbers would be nice.
>> I haven't benchmarked anything, which makes me very uneasy. All
>> I've checked is that the system boots, and FWIW I appreciate no
>> difference in boot time.
> No decrease in boot time is good. We /know/ we're saving memory, after all.
>   
>> Is there a benchmark suite to test TCG changes?
> No, sorry.
>
>
> r~

Benchmarking TCG with QEMU's system emulation is nearly impossible
because operating systems usually contain lots of timer based operations.
The TCG interpreter for example is really slow, but a BIOS will boot
faster than expected with it.

The user mode emulation is much better for benchmarks.
Run some command line Linux application which mainly does
computations (not file i/o) using user mode emulation on Linux.
The OpenSSL package contains bntest which can be used
as a benchmark for TCG. Redirect all output to /dev/null when
you run it.

Binaries for i386 and x86_64 are available from
http://qemu.weilnetz.de/test/user/.

Stefan