[Unison-hackers] Memory exhaustion issue (#1068)

[Tõivo Leedjärv]

On Sun, 24 Nov 2024 at 16:51, Michael von Glasow <michael at vonglasow.com> wrote:
>
> What I do not understand: why would simply copying a file in its
> entirety, without looking at it any further, consume any significant
> amounts of memory? The transmitting end would read the file sequentially

Except that it doesn't. If it would, that would be a bug.
My testing with the minimal roots showed no such excessive memory
usage (the few MB used are normal for GC working). My suspicion is
still on the overall archive size (it's the number of items that
matters, file sizes don't matter at all); that's why it would be good
for you to repeat testing with empty roots.

> passes of filling the buffer. Or am I overlooking something?

No, you're not overlooking something. You might just be focusing on
the wrong "cuplrit" because GC works differently during file copy
(that is to say, it can't free something that is in use), so you see
the symptoms of memory exhaustion. But the cause is elsewhere and not
related to the copy or size of the file (larger sizes only mean that
memory can't be freed for a longer time). Or so it's a bug somewhere.