Date: Sun, 8 Nov 1998 02:14:13 +0100 From: Eivind Eklund <eivind@yes.no> To: John Fieber <jfieber@indiana.edu>, Alexander Litvin <archer@lucky.net> Cc: Brian Feldman <green@unixhelp.org>, current@FreeBSD.ORG Subject: Re: The infamous dying daemons bug Message-ID: <19981108021413.48676@follo.net> In-Reply-To: <Pine.BSF.4.05.9811070904250.482-100000@fallout.campusview.indiana.edu>; from John Fieber on Sat, Nov 07, 1998 at 09:16:27AM -0500 References: <199811071314.PAA23544@grape.carrier.kiev.ua> <Pine.BSF.4.05.9811070904250.482-100000@fallout.campusview.indiana.edu>
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On Sat, Nov 07, 1998 at 09:16:27AM -0500, John Fieber wrote:
> On Sat, 7 Nov 1998, Alexander Litvin wrote:
>
> > In article <Pine.BSF.4.05.9811061814370.6415-100000@janus.syracuse.net> you wrote:
> > BF> I haven't had this bug. And a 3.0 box at school doesn't have it either...
> > BF> it's not as common as you think.
> >
> > Have you beaten your systems to "swap_pager: out of swap space"?
>
> The meaning of this messages is reasonably clean and I have seen
> it before (although not since upgrading to 3.0 and meeting the
> dying daemons bug), but I have on occasion seen:
>
> smap_pager: suggest more swap space: 125 MB
>
> I assume it is a warning that I'm about to run out, but what does
> the 125MB mean?
I believe (and this is not confirmed) that this mean that you are
overcommitting 125MB of memory - that is, there are 125MB of allocated
pages that don't have backing swap space if you dirty them.
Looking at sys/vm/swap_pager.c, it looks like this guess is correct -
but there is a 2x multiplier in there that seems to mean it is
suggesting 2x the amount of overcommit. This is the relevant
code-fragment:
if (!suggest_more_swap && (vm_swap_size < btodb(cnt.v_page_count * PAGE_
SIZE))) {
printf("swap_pager: suggest more swap space: %d MB\n",
(2 * cnt.v_page_count * (PAGE_SIZE / 1024)) / 1000);
suggest_more_swap = 1;
}
Eivind.
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