On Dec 19, 2007, at 3:48 PM, Gus Wirth wrote:
The kernel probably doesn't have HIMEM enabled. I have 1GB RAM in my
system. From my own running kernel, extracted from dmesg:
Ah! You're exactly right... from sparky's kernel:
Warning only 896MB will be used.
Use a HIGHMEM enabled kernel.
896MB LOWMEM available.
Anyway... as much as memory might help, it turns out that it was *not*
a Zope load issue which caused the sluggishness.
On Jim's suggestion, I went into Sparky to shut down Zope temporarily
to see how much effect it would have on the load. Turns out very
little... system load in the VM was still hovering around 2, even with
Zope unloaded and free memory available. Realizing that something
wasn't right, I went out to dom0 to see what was going on, and in
dmesg I found an endless stream of "BUG: soft lockup detected on
CPU#0!" errors, with CPU# varying from 0 to 3. After each error was
some sort of symbol dump. A bit of Googling turned up a lot of hits,
but the first result I found from a Xen environment seemed to indicate
that this was the result of some obscure bug known to be in RedHat's
original upstream kernels, but now fixed with subsequent updates.
Seeing that, and realizing that Sparky's dom0 was still running CentOS
5.0, I went ahead and did the round of updates that brought it to the
much-improved CentOS 5.1 (which included a ton of Xen-related fixes),
at the same time bringing in the latest RedHat kernel. After reboot,
everything is now running swimmingly, at 0.14 utilization and 100MB of
free RAM even with Zope loaded.
I realize this isn't exactly a satisfactory explanation, since Sparky
ran just fine under the older kernel for months. I'm not sure what
changed (or eventually degraded) to cause this sort of BUG to rear its
head. In fact, it could come back again. I guess time will tell.
Nonetheless, I will still be moving Zope to a newer paravirtualized VM
with sufficient RAM... but I'm leaving for vacation on Friday so it
may have to wait until January. I will have my laptop and some free
time while on vacation, so if I get sick of the Wyoming cold and snow
maybe I'll get it done sooner. :)
--
Joshua Penix http://www.binarytribe.com
Binary Tribe Linux Integration Services & Network Consulting
--
[email protected]
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