Not sure where the appropriate section is for this post. Mods feel free to move elsewhere.
tl; dr Conclusions:
1) gcc 4.8.0 compiles ~ 5% slower than gcc 4.7.2 compiles.
2) gcc 4.8.0 produces kernels that run slower when compiling than kernels produced by gcc 4.7.2.
I read the Intel i7 gcc 4.8 benchmark piece that Phoronix published a week ago wherein they noted some significant slow downs in the 4.8 series. Now that 4.8.0-1 hit [testing] I wanted to see how the two version compared using a compilation based endpoint with `make -j8 bzImage` in the latest linux package being the test. This run was repeated 10 times (threw out the first run as a warm up). Results were analyzed in a oneway ANOVA.
Test machine: Intel i7-3370k @ 4.5 GHz/16 GB RAM running Arch 86_64.
Four test conditions:
1) linux-ck-3.8.5-1 (build with gcc-4.7.2-4) running the benchmark with gcc-4.7.2-4; blue in the graphic below.
2) linux-ck-3.8.5-1 (build with gcc-4.7.2-4) running the benchmark with gcc-4.8.0-1; green in the graphic below.
3) linux-ck-3.8.5-2 (build with gcc-4.8.0-1) running the benchmark with gcc-4.7.2-4; pink in the graphic below.
4) linux-ck-3.8.5-2 (build with gcc-4.8.0-1) running the benchmark with gcc-4.8.0-1; yellow in the graphic below.
*Compare median blue to green or compare median pink to yellow; result is the 4.8 version of gcc gives ~5 % decrease in efficiency as measured by compilation time.
*Compare median green to yellow; result is that the kernel compiled with 4.8.0-1 runs slower as measured by this end-point. Yes, it is a trivial slow down of ~272 ms but that slow down is statistically significant.
Last edited by graysky (2013-03-30 14:33:40)