[cfe-dev] How much profile data is enough for pgo?

[Xinliang David Li via cfe-dev]

It is not the number of packages that matter, but the coverage of the hot
paths that matters. For instance if you build a lot of packages but they
are all written in C, the profile will miss many paths related to C++ such
as template handling.  The options used in the package builds are also
important.

To curate the training data, one way is to find the most time consuming
part of your build and select those. The profile merge tool also support
merging with weights.

thanks,

David

On Thu, Oct 7, 2021 at 1:10 PM Tom Stellard via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Hi,
>
> I'm trying to generate profile data for clang by building the some of the
> packages
> we ship in Fedora Linux.  I'm trying to decide how many packages to build,
> is
> there much advantage to building 1000 vs something substantially less,
> like 100?
>
> -Tom
>
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