On Tue, Oct 3, 2017 at 4:19 PM, Simon Sapin <simon.sa...@exyr.org> wrote:
> On 03/10/2017 21:51, Nicholas Matsakis wrote:
>>
>> That said, the measurements I just did today still showed big wins
>> (~3x), at least for the sample changes that I've been making (adding
>> new methods, changing method bodies in style). So it may be worth
>> testing.
>
>
> This 3x is what compared to what?
Specifically, what I did was:
- Check out tip of servo and latest nightly
- Configure servo to use "system rust" and to enable incremental
- Build once
- Apply diff
- Built again, measuring time
And I compared those results against the same set of steps, but
without incremental enabled. I found:
- Build times were 3x better (~400s vs ~1400s)
- Memory use was about 2x worse (7G peak vs 4G peak)
- Disk space consumed for incremental state was 1.5G
> FWIW, my "5x slower" figure was building the script crate ("mach build -p
> script" where the dependencies are already compiled) soon after upgrading
> rustc (so possibly with no relevant incremental cache entries) to
> 1.22.0-nightly (c6884b12d 2017-09-30).
5x slower than what?
> It’s not representative of any real workflow, but so
> far the results had not been absurdly different from making a read code
> change. Maybe the red/green system will change that?
I do expect so, though not *immediately* upon landing.
> A real change that could occur during debugging and that’s easy to reproduce
> at any base commit is adding println!("{:#?}", some_variable) at a random
> place in the code.
This was indeed one of my two patches -- well, something very similar.
The other was adding a new method that was not otherwise used (which
is probably less representative).
Niko
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