Date: Tue, 21 Aug 2001 12:07:13 -0700 (PDT) From: Matt Dillon <dillon@earth.backplane.com> To: Steve Shorter <steve@nomad.tor.lets.net> Cc: freebsd-stable@FreeBSD.ORG Subject: Re: VM exhaustion and kernel hangs Message-ID: <200108211907.f7LJ7DK65902@earth.backplane.com> References: <20010821115724.A2562@nomad.lets.net> <200108211820.f7LIKZf65278@earth.backplane.com> <20010821144406.A2733@nomad.lets.net>
next in thread | previous in thread | raw e-mail | index | archive | help
:>
:> You might also want to try to figure out what is eating up the memory
:> (or, more specifically, dirtying memory since clean file-backed pages
:> would not lead to this situation).
:>
:
: Can this situation be created if a web server is serving pages
:that are being modified by another process, if they are both accessing the
:fs over NFS?
:
: thanx - steve
No. What creates this situation tends to be malloc()'d data (which is
not backed by a file), or MAP_PRIVATE file memory mappings which are
modified. If you are running a large number of processes the situation
can also occur simply due to the modified data/bss areas of the programs
in question, and do to the modified pages of 'glue' used to tie the
shared libraries together.
In a turnkey environment the shared library glue can be gotten rid of
by compiling the programs -static, leaving only data/bss and malloc()
space left.
What you need to do is determine exactly what is causing the system
to run out of memory. For example, if you are running apache you may
need to limit the number of daemons it forks off or limit the number of
requests each one takes before Apache respawns it. It is simply not
possible to give any on-the-mark recommendations until you know exactly
what is eating the memory.
Also, just to throw this out... swap over NFS is not actually all that
bad a thing to do, especially with FreeBSD-4.x and modern switched
100BaseTX ethernet links.
-Matt
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-stable" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200108211907.f7LJ7DK65902>