Messages in this thread | | | Date | Wed, 15 Oct 2003 16:52:05 -0700 | From | Andrew Morton <> | Subject | Re: [2.6 patch] add a config option for -Os compilation |
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Adrian Bunk <bunk@fs.tum.de> wrote: > > On Wed, Oct 15, 2003 at 04:12:51PM -0700, Andrew Morton wrote: > >... > > They are small concerns really, but it does make one wonder why we should > > not make this change unconditional: just switch the kernel to -Os? > > > > Does anyone have any (non-micro-)benchmark results which say this is a bad > > idea? > > No benchmarks, only arguments: > > - it's less tested (there might be miscompilations in some part of the > kernel with some supported compilers)
Testing is not a problem.
> - there might be fast path code somewhere in the kernel that becomes > significantely slower with -Os
I really doubt it. Kernel CPU footprint is dominated by dcache misses. If -Os reduces icache footprint it may even be a net win; people tend to benchmark things in tight loops, which favours fast code over small code.
> - I've already seen a report for an ICE in gcc 2.95 of a user compiling > kernel 2.4 with -Os [1]
Well there's only one way to find out if we'll hit that. How's about you cook me a patch which switches to -Os unconditionally and we'll see how it goes?
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