Re: [patch 00/2] improve .text size on gcc 4.0 and newer compilers

Martin Bligh
2006-01-05T22:54:49Z

>>>What I was proposing was something like, say, arch/i386/popularity.lst,
>>>which would simply contain a list of the most popular n% of functions
>>>sorted by popularity. As text, of course.
>>
>>I suspect that would certainlty work for pure function-based popularity,
>>and yes, it has the advantage of being simple (especially for something
>>that ends up being almost totally separated from the compiler: if we're
>>using this purely to modify link scripts etc with special tools).
>>
>>But what about the unlikely/likely conditional hints that we currently do
>>by hand? How are you going to sanely maintain a list of those without
>>doing that in source code?
>
>
> Dunno. Those bits are all anonymous so marking them in situ is about
> the only way to go. But we can do better for whole functions.

Would also make it easier to rank it as a percentage, or group by
locality of reference to other functions, rather than just a binary
split of "rare" vs "not-rare".

Of course it's all very dependant on workload, which drivers you're
using too, etc, etc. So a profile that's separate also makes it much
easier to tweak for one machine than the source base in general, which
theoretically represents everyone (and thus has little info ;-)).

Which also makes me think it's easier to mark hot functions than cold
ones, in a more general maintainance sense.

M.