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Re: WHOPR partitioning algorithm
I have not followed the thread carefully, but what is the advantage of
doing code layout in IPO instead of doing this at link time? The
support of user directed code and data layout is already in gold (and
mozilla folks have tried this functionality to layout functions
according to load time affinity data collected by instrumentation and
got large speed up). The remaining part of the support is also almost
ready but not yet submitted upstream (needs more tuning on various
targets): 1) the compiler part of the support (e.g. writing down call
graph hot edges as note sections for linker to consume; 2) the code
layout algorithm in linker using the data from the compiler.
Thanks,
David
On Mon, Sep 6, 2010 at 10:27 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
>> > What I would like to also support in longer run is profile feedback
>> > specifyingTh
>> > in what order the functions are executed at runtime and laying code based on
>> > that to optimize startup times.
>>
>> btw, what about a profile driven partitioning algoritm, like LIPO?
>
> Well, AFAIK LIPO is not shooting for code layout.
>
> Current algorithm (and the planned function reordering pass) both use callgraph edge
> frequencies that are profile driven too.
>
> Honza
>>
>> Ciao,
>> Steven
>