[llvm] r212816 - raw_svector_ostream: grow and reserve atomically

[Chandler Carruth]

On Fri, Jul 11, 2014 at 7:02 AM, Alp Toker <alp at nuanti.com> wrote:

> Author: alp
> Date: Fri Jul 11 09:02:04 2014
> New Revision: 212816
>
> URL: http://llvm.org/viewvc/llvm-project?rev=212816&view=rev
> Log:
> raw_svector_ostream: grow and reserve atomically
>
> Including the scratch buffer size in the initial reservation eliminates the
> subsequent malloc+move operation and offers a healthier constant growth
> with
> less memory wastage.
>

What benchmarks did you run to measure the memory waste, and what were the
numbers? I think it is really important to provide these kinds of details
with potentially performance impacting changes like this.

I also think it would have been better to provide those details in a
pre-commit review so that other users of LLVM could let you know if their
use cases differ significantly and would therefore have significantly
different performance tradeoffs. No need to revert the patch (others can
chime in on this review thread if it matters to them) but for future
reference when changing the Support libraries.

-Chandler
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