Messages in this thread | | | Date | Tue, 04 Feb 2003 07:50:59 -0800 | From | "Martin J. Bligh" <> | Subject | Re: [Lse-tech] gcc 2.95 vs 3.21 performance |
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> > People keep extolling the virtues of gcc 3.2 to me, which I'm > > reluctant to switch to, since it compiles so much slower. But > > it supposedly generates better code, so I thought I'd compile > > the kernel with both and compare the results. This is gcc 2.95 > > and 3.2.1 from debian unstable on a 16-way NUMA-Q. The kernbench > > tests still use 2.95 for the compile-time stuff. > > > > The results below leaves me distinctly unconvinced by the supposed > > merits of modern gcc's. Not really better or worse, within experimental > > error. But much slower to compile things with. > > What kernel was kernbench compiling ? The reason I'm asking is that > 2.5s (and more recent 2.4.21pre's) will use -march flags for more > aggressive optimisation on newer gcc's. > If you want to compare apples to apples, make sure you choose > something like i386 in the processor menu, and then it'll always > use -march=i386 instead of getting fancy with things like -march=pentium4
Kernbench compiles 2.4.17, because I'm old, slow and lazy, and that was what was around when I started doing this test ;-)
But the point is still the same ... even if it is doing more agressive optimisation, it's not actually buying us anything (at least for the kernel)
M.
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