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Date:      Sun, 21 Apr 2002 20:50:40 -0300 (ADT)
From:      "Marc G. Fournier" <scrappy@hub.org>
To:        Terry Lambert <tlambert2@mindspring.com>
Cc:        freebsd-current@freebsd.org, <freebsd-stable@freebsd.org>
Subject:   Re: FreeBSD 4.5-STABLE not easily scalable to large servers ... ?
Message-ID:  <20020421201025.C1721-100000@mail1.hub.org>
In-Reply-To: <3CC26C91.C81002ED@mindspring.com>

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On Sun, 21 Apr 2002, Terry Lambert wrote:

> "Marc G. Fournier" wrote:
> > > You have more memory than you can allocate kernel memory to
> > > provide page table entries for.
> > >
> > > The only solution is to increase your kernel virtual address
> > > space size to accomodate the page mappings.
> > >
> > > How to do this varies widely by the version of FreeBSD you are
> > > using, and, unless you read "NOTES" and are running a recent
> > > -current, is not incredibly well documented, and requires an
> > > understanding of how the virtual address space is laid out and
> > > managed (which is also not well documented anywhere).
> >
> > Ya, this is the roadblock I'm hitting :(  I'm running 4.5-STABLE here, as
> > of this afternoon ... thoughts/suggestiosn based on that?
>
> Read the handbook as it existed for 4.5-STABLE, and read NOTES.
> It (sorta) tells you how to increase your KVA size.
>
>
> > Also, is there somethign that I can run to monitor this, similar to
> > running netstat -m to watch nmbclusters?
>
> DDB?  8-) 8-).
>
> No, there's no stats collected on this stuff, because it's a
> pretty obvious and straight-forward thing: you have to have a
> KVA space large enough that, once you subtract out 4K for each
> 4M of physical memory and swap (max 4G total for both), you
> end up with memory left over for the kernel to use, and your
> limits are such that the you don't run out of PTEs before you
> run out of mbufs (or whatever you plan on allocating).

... and translated to english, this means? :)

Okay, I'm going to assume that I'm allowed 4Gig of RAM + 4Gig of Swap, for
a total of 8Gig ... so, if I subtract out 4K for each 4M, that is 8M for
... what?

So, I've theoretically got 8184M of VM available for the kernel to use
right now?  what are PTEs and how do I know how many I have right now?  as
for mbufs, I've currently got:

jupiter> netstat -m
173/1664/61440 mbufs in use (current/peak/max):
        77 mbufs allocated to data
        96 mbufs allocated to packet headers
71/932/15360 mbuf clusters in use (current/peak/max)
2280 Kbytes allocated to network (4% of mb_map in use)
0 requests for memory denied
0 requests for memory delayed
0 calls to protocol drain routines

	So how do I find out where my PTEs are sitting at?




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