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

[megane]

Sven Hartrumpf <hartrumpf@gmx.net> writes:

> Hi Mario.
>
[snip]
> Run options are:
>
> -:hi256m -:H -:hs0 -:o -:s4096k

Hi Sven,

The combination of -:hi256m and -:hs0 pretty much guarantees these
patches won't help you.

- The first patch would bump the heap size up if your program constantly
  needed, say 255.99MB of memory (so it'd generate 10k of garbage, run major
  gc, generate 10k of garbage, run major gc, ...). So, if you've chosen
  256m conservatively, taking your input data into account, the patches
  don't help.
- The second patch is a simple hysteresis control that mitigates rapid
  heap size yo-yo-ing. Using -:hs0 prevents that completely.

Also, there won't be that much speed-up if the major-gc-time to
total-run-time ratio is low to begin with.