From: Eric Wong <normalperson@...>
Date: 2018-08-01T07:34:31+00:00
Subject: [ruby-core:88253] Re: [Ruby trunk Feature#14955] [PATCH] gc.c: use MADV_FREE to release most of the heap page body

ko1@atdot.net wrote:
> It causes system call and extra overhead so that I'm not sure
> it is acceptable.
> On previous proposal I could measure some performance down on
> fine-grain madvise.

OK.  I am worried about that, too.

For this, I think we can also track age of page in tomb before
deciding to free or madvise.  That can also reduce fragmentation
from the "aligned_free && memalign soon-after" case.

> https://bugs.ruby-lang.org/issues/12236

> I assume that we need to make sequential groups. 16KB (4 pages) group can be enough (but not sure).

Yes, 16KB is tiny; but it also helps reduce pause time on lazy-sweep.
Tradeoffs...

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