Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?

[Richard Henderson <rth@twiddle.net>]

On 08/19/2015 07:41 AM, Artyom Tarasenko wrote:
> Without the patch:
>
>   time g++ -DHAVE_CONFIG_H -I. -I../binutils-gdb/gold
> -I../binutils-gdb/gold -I../binutils-gdb/gold/../include
> -I../binutils-gdb/gold/../elfcpp
> -DLOCALEDIR="\"/usr/local/share/locale\""
> -DBINDIR="\"/usr/local/bin\"" -DTOOLBINDIR="\"/usr/local//bin\""
> -DTOOLLIBDIR="\"/usr/local//lib\""   -W -Wall    -Werror
> -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -frandom-seed=tilegx.o
> -I../binutils-gdb/gold/../zlib -g -O2 -MT tilegx.o -MD -MP -MF
> .deps/tilegx.Tpo -c -o tilegx.o ../binutils-gdb/gold/tilegx.cc
>
> real    18m31.407s
> user    18m23.661s
> sys     0m6.784s
>
> The patch surely improves the situation, tcg_optimize in the perf top
> takes ~7% (instead of~12%), and the only function marked red by
> perf-top is init_temp_info(). So with the patch:
>
> real    17m46.380s
> user    17m37.522s
> sys     0m7.120s
>
>
> And if I completely disable optimizer (// #define
> USE_TCG_OPTIMIZATIONS in tcg.c), it's still quite faster:
>
> real    14m17.668s
> user    14m10.241s
> sys     0m6.060s

This isn't surprising, because at the moment tcg optimizations are almost 
completely ineffective for sparc.  The way the register windows are implemented 
means that there are very few proper tcg temporaries to optimize.

I've just updated an old branch that attempts to cure this.  It creates proper 
tcg temporaries for the windowed registers, and uses a bit of recursion to find 
the place at which they should be stored.

   git://github.com/rth7680/qemu.git tcg-indirect

With a few quick unscientific tests, it appears to help.  It would be nice to 
put that branch side-by-side with your tests above.


r~