[PATCH] D20993: Add support for collating profiles for use with code coverage

[Xinliang David Li via llvm-commits]

On Fri, Jun 10, 2016 at 4:35 PM, Vedant Kumar <vsk at apple.com> wrote:

> vsk added a comment.
>
> In http://reviews.llvm.org/D20993#454452, @davidxl wrote:
>
> > Why choosing default size of 9? Do you have build time comparison
> numbers i.e., pool size from 1 to 9?
>
>
> I chose 9 because it's the highest option: a larger pool of raw profiles
> should theoretically lead to less lock contention. Ideally this would be
> some factor of the number of threads on the system. However, I don't think
> it's worth optimizing this default.
>
>
That is fine. My recollection is that 9 or larger is only needed when
network storage system is used. For local HDD, the performance flats out
quickly at pool size of 3 or 4 so you get diminishing returns while the
storage size cost and post-processing time is increased.  For SSD, 1 is
just as good as 2 or higher.


David


> > Also, writing it in Python makes it pretty portable for free and is
> generally more readable.
>
>
> Sure, I'll upload a new diff with this change.
>
>
> http://reviews.llvm.org/D20993
>
>
>
>
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