Re: -O2 vs -O3

From: willy@thepuffingroup.com
Date: Wed May 24 2000 - 15:21:41 EDT

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    On Wed, May 24, 2000 at 09:48:19AM -0600, Christopher Thompson wrote:
    > Brief question:
    >
    > Linux kernels are compiled with the -O2 flag set. I'm curious, why don't we
    > use -O3?

    -O3 introduces some optimisations which may not be appropriate for the
    kernel. In particular, it tries to know better about function-inlining.
    It is asserted (note I don't necessarily agree with the assertion :-)
    that the kernel developers in their infinite wisdom have analysed which
    functions would best be inlined and which are best out-of-line.

    > Also, is it now safe to compile the 2.3.99-prex kernels with gcc 2.95.2 instead
    > of 2.7.2.3?

    not sure. most people seem to, but if you run into any problems, it's
    normally advised that you should drop back to 2.7.2 to verify them.

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