Re: [PATCH 1/2] Prevent excessive major gcs by having decent amount of unused heap

[Mario Domenech Goulart]

Hi,

On Wed, 08 Jan 2020 17:03:25 +0200 megane <meganeka@gmail.com> wrote:

> The garbage collector currently has couple of less than optimal
> behaviors:
>
> 1. If there's constantly only a small amount of heap left after a major
>    collection then there will be constant major collections.
>
> 2. If the used heap space does yo-yo then there will be constant heap
>    resizes.
>
>
> These patches are for those two cases.
>
> Benchmarks for the 1st patch:
>   http://paste.call-cc.org/paste?id=02242cbbd2c79456920d8dfdb327b791231eefd2
>   
> http://paste.call-cc.org/paste?id=02242cbbd2c79456920d8dfdb327b791231eefd2#a1
>
>   - note the up-to 2x speedup in some cases
>
> Benchmarks when both patches applied:
>   
> http://paste.call-cc.org/paste?id=02242cbbd2c79456920d8dfdb327b791231eefd2#a2
>
>   - see especially kernwyk-string
>
> Some picks:
>
>   Vanilla master:
>
>   Total run time (CPU time):      5m39.5449999999999s
>   Total time spent in major GCs:  54.041s
>   Total number of major GCs:      39245
>
>   With -:hf4M
>
>   Total run time (CPU time):      4m57.9510000000001s
>   Total time spent in major GCs:  15.862s
>   Total number of major GCs:      4766

To celebrate the one-year anniversary of the submission of these patches
I pushed them.

I ran a relatively extensive set of benchmark configurations comparing
CHICKEN from master against CHICKEN from master plus the patches.
Results are here: http://parenteses.org/mario/misc/benchmarks-megane/

I could not find any significant performance degradation with the
patches.  The only degradations were very small, below the 5% deviance
or large differences in tiny timing values, which I'd consider noise.
On the other hand, the performance increase is quite significant and far
from being noise, as far as I can tell.

Thanks for the patches and for your patience, megane.

All the best.
Mario
-- 
http://parenteses.org/mario