System crashing when swap hits 25%

[Simon Slater]

On Tue, 2008-03-11 at 12:53 -0400, Chris Snook wrote:
> Simon Slater wrote:
> > On Mon, 2008-03-10 at 21:01 -0400, Chris Snook wrote:
> >>>> sysrq-m and sysrq-t data out of the system.  You'll want to set 
> >>>> kernel.sysrq=1 first. 
> >>> Where do I find these?
> >>>
> >> There are two interfaces.  One is the /proc/sys directory, and the
> >> other 
> >> is sysctl.  If you want to set something with sysctl, the easy way is
> >> to 
> >> add a line in sysctl.conf (for example: vm.overcommit_memory=2) and
> >> then 
> >> run sysctl -p to process the config file again.
> >>
> > 	Have just been through a few man pages.
> > Temporarily, the command sysctl vm.overcommit_memory=2 would do the job?
> 
> By itself, probably not.
> 
> > What does the value '2' signify?
> 
> 0 = heuristic overcommit
> 1 = always overcommit (until completely out of RAM + swap)
> 2 = overcommit (swap + (vm.overcommit_ratio * RAM))
> 
> > What do sysrq-m and sysrq-t do?  I haven't found them yet.
> 
> alt+sysrq+m prints memory statistics
> alt+sysrq+t prints thread state information

Silly me. It's been so long since I used that key I forgot it is there.
> 
> > Oh, currently vm.overcommit_memory=0 and kernel.sysrq=0.
> 
> You'll need to set kernel.sysrq=1 for keyboard sysrq input to be 
> honored.  If you set vm.overcommit_memory=2, then vm.overcommit_ratio 
> will be honored.
> 
> -- Chris
> 
	I used sysctl vm.overcommit_memory=2 and checked for badblocks in the
swap file (none found) and performance is amazing.  This is very
subjective, but I can load and run so much more and I'm sure things are
runnung faster.

	At the moment the panel applet is at the point where things usually
hang.  free reports:
[simon at Ipex ~]$ free
             total       used       free     shared    buffers
cached
Mem:        515220     509020       6200          0       5596
215728
-/+ buffers/cache:     287696     227524
Swap:      1048568     213904     834664
However, rather than the usual 2 or 3 apps with a few browser tabs open
when things hang, at the moment I have: terminal; Firefox with 20 tabs;
2x Konqueror one with 3 tabs; Evolution downloading email and
spamassassin; 24 OOWriter docs; 6 OOImpress presentations; 11 Kpdf with
11Mb pdf and 1 10Mb pdf; 13 brochures open in Evince; 2 tty sessions
with 1 running an smbtar script and jobs to the printer.  This is
amazing.

	I'll push things further now to see what happens as swap increases.

-- 
Regards
Simon