[Sks-devel] Clocks, timers, PTree and wiki advice

[Phil Pennock]

Okay, we appear to have two people for whom the TSC clocksource in the
kernel fixes PTree corruption, so I've currently got this in the wiki:

  Virtual Machine issues

  There are some issues with clock-keeping mechanisms in some virtual
  machines (VMs) affecting the Berkeley DB used for PTrees; if the clock
  resolution is too low, multiple entries occur at the same timestamp
  and the DB becomes corrupted.

  If you are running Linux inside a VM, then pass clocksource=tsc as
  part of the kernel command-line in Grub/Lilo/... to switch the VM's
  timer-system away from Jiffies towards the Time Stamp Counter of the
  processors. Note that this can itself be problematic with older
  kernels locking up on SMP instances. If running SKS in a VM instance,
  you should probably constrain it to a single CPU.

http://code.google.com/p/sks-keyserver/wiki/Peering  (er, kernel
configuration in a page about peering ... ah well).

Does this make sense to the folks who've encountered and fixed this
problem?  Is it accurate?

I wonder whether people setting up or buying VMs tend to have a VM per
job they run, or be buying a "personal toy" VM with a whole bunch of
different things running, so that the single CPU constraint might be an
issue.  I also have usually run systems on bare metal, rather than in
VMs, so this is beyond my expertise.  Folks?

-Phil