"Benchmarking BSD and Linux"

Matthew Dillon dillon at apollo.backplane.com
Tue Mar 8 18:53:14 PST 2011

   After playing with this a bit today I found that a large chunk of the
   difference seems to be related to the caching of various structures
   related to process fork()ing, such as thread and kernel stacks, vmspace
   structures, process structures, and so forth.

   I made a few commits to make some of these parameters tunable, then
   tuned them up to absurd levels in /boot/loader.conf (requiring a reboot):


   And the results were as expected.  A much flatter, curve.

   I have to say though that this is NOT a good idea in general.  FreeBSD
   just should not be trying to cache thousands of threads worth of
   structures and associated data... it should be throwing that away to free
   up memory for other purposes, and probably contributes to KVM fragmentation
   as well.  Even though it makes the fork benchmark look better it is
   a bad idea for a production system.


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