On Thu, 2007-08-09 at 12:11 +0200, Pavel Machek wrote:
Hi!
quoted
I've been working on this for quite some time. And should post again
soon. Please see the patches:
http://programming.kicks-ass.net/kernel-patches/vm_deadlock/current/
For now it requires one uses SLUB, I hope that SLAB will go away (will
save me the trouble of adding support) and I guess I ought to do SLOB
some time (if that does stay).
You'd need the first 22 patches of that series, and then call
sk_set_memalloc(sk) on the proper socket, and do some fiddling with the
reconnect logic. See nfs-swapfile.patch for examples.
What do you use for testing? I set up ata over ethernet... swapping
over that should deadlock w/o your patches.
But I'm able to compile kernel (-j 10) on 128MB machine, and I tried
cat /dev/zero | grep foo to exhaust memory... and could not reproduce
the deadlock. Should I pingflood? Tweak down ammount of atomic memory
avaialable to make deadlocks easier to reproduce?
I usually test swap over NFS in the following manner, I setup a regular
inet service on the machine (apache or a bunch of ncat sockets piping to
files or something) and run a heavy workload on the machine (128M):
2*64M file backed thrashers and 2*64M anonymous thrashers. Then I start
clients for the regular inet service, wait for a bit, and shut down the
NFS server.
This makes the machine grind to a halt, I then restart the NFS server,
wait for it to reconnect and the client to come alive again.
Without the last few swap-over-NFS patches this last bit - getting back
out of that situation - never happens.
The basic idea is to make connectivity to the machine where swap traffic
goes very hard (pull a cable, cleanly shut down the server) and to keep
other network traffic pounding the machine.