Re: Larger GC thresholds for non-interactive Emacs

[Ihor Radchenko]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> I also took a look at related data.  E.g. comparing p=1.0 to the old
> p-0.1 on the process that performs the highest number of GCs (188 cycles
> with p=1.0 and 650 cycles with p=0.1) during an Emacs build.  Here are
> the corresponding last few GC cycles:
>
>     % grep GC-26227 ./+make-0.1.log | tail -n 10              
>     GC-26227 p=0.1 total=18.8M free=1.9M thresold=1.9M
> ...
>     GC-26227 p=0.1 total=145.7M free=32.6M thresold=14.6M
>     GC-26227 p=0.1 total=132.8M free=60.7M thresold=13.3M
>     % grep GC-898 ./+make-1.0.log | tail -n 10              
>     GC-898 p=1.0 total=18.5M free=7.5M thresold=18.5M
> ...
>     GC-898 p=1.0 total=145.7M free=32.6M thresold=145.7M
>     % 

I feel that I am confused about this data.

We have gc-cons-threshold and gc-cons-percentage

According to the gc-cons-percentage docstring:

>> If this portion is smaller than `gc-cons-threshold', this is ignored.

which implies that gc-cons-percentage only takes effect when
heap_size * gc-cons-percentage >= gc-cons-threshold (= 0.8M)

So, heap_size should be >= 80M to take effect at p=1.0
and heap_size should be >= 800M to take effect at p=0.1

yet, you do see an effect at total=18.5M.

What am I missing?

Best,
Ihor