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f : 26 April 2012 • 5:33PM -0400

Re: FreeBSD vice OS X memory management
by Michael Powell


Adam Vande More wrote:

> On Thu, Apr 26, 2012 at 12:04 AM, jb <jb.1234abcd@gmai...> wrote:
>> If so, should FreeBSD adopt NetBSD's MM subsys, or just improve itself
>> surgically ?
> You ought first establish there is a problem.  What you have cited is
> recently reinvigorated trend that has taken on the air of  the "BDS is
> dying" troll.  What you have is a set of computer users with no
> understanding of kernel internals attempting to diagnose some sort of
> possibly legitimate problem by reaching conclusion via rumor and
> guesswork.  These people can be taken about as seriously as those who
> insist the moon landing was fake and other bizarre ignorant
> pseudo-science.
> When you have a test case illustrating your feared FreeBSD VM
> shortcomings, you may at that point begin to attract developer interest.

To the OP:

A potential first test case where the symptom is "my system slows to a crawl
and starts paging out to disk" might be to build a kernel with the
SCHED_4BSD scheduler. There have been a couple of edge/corner cases that
sound like this. That is, if you really have a problem and want to try
eliminating one possibility.

Another thing that shows up in things like top is it breaks and does not
report accurate values for anything when userland and kernel are out of
sync, that is if it runs at all without segfaulting. World and kernel being
out of sync would be operator error. In this case the values you are using
to somehow relate the symptom to memory management would be false.

As far as all the rest, such as something being "deeply broken in OS X
memory management", mentions of NetBSD memory management, etc, are all  
irrelevant. It is this wild mix of stuff seemingly non-related to any problem
in FreeBSD per se, that makes this look like a troll.

If you really are having a problem with FreeBSD you are going to have to do
a lot better than this in terms of providing some data points which define
the problem. I am in agreement with Adam here: either you can work the
problem or you can troll. I don't see any indication yet of any real problem
analysis, only a wild mix of stuff non-related to FreeBSD sprinkled with some
magic 'memory management' dust.

Sorry if this comes across the wrong way, but this really looks like troll
material to me too - it has a great resemblance to a pattern trolls have
used for many years.


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