On 5/16/06, James Ausmus <[EMAIL PROTECTED]> wrote:
> Does the `O' (uppercase oh) have an `s' component? > Yes - the -O setting is the level of code optimization that gcc does - -Os is very similar to -O2, but also does code size optimization, which may, under some circumstances, result in slower performance, but will also, in other circumstances, result if faster performance.
BTW, I measured the performance differences for the things I care about (compression, media encoding, and dm-crypt encryption), and ended up choosing -Os for my Core Duo system. As James says, some things run faster, other things run slower. And it isn't across the board...bzip2 -1 can give completely different results than bzip2 -9. The differences generally are within +/- 10% of the -O2 performance. The major advantage to -Os (aside from smaller executables), is compile time. Especially C++ programs take noticably less time to compile with -Os than with -O2 or -O3. -Richard -- [email protected] mailing list
