i thought this was interesting. this is from a small, 1 package
system. it gives a feel for the basic performance of the quick
list allocb under low load, which isn't too bad:
this is just after boot,
ivey# awk '$1=="allocb" {printf "%s\t%d\n", $0, int($4/$3)}' < /dev/swap
#quicklist sz count cycles cycles/alloc
allocb 128: 8595 2043800 237
allocb 1520: 29 236908 8169
allocb 9000: 119 105680 888
allocb 16384: 7174 1923500 268
allocb 65536: 122 66280 543
and this is after pushing a bit of tcp:
ivey# awk '$1=="allocb" {printf "%s\t%d\n", $0, int($4/$3)}' < /dev/swap
allocb 128: 38084 7199704 189
allocb 1520: 56139 9075432 161
allocb 9000: 10127 2437248 240
allocb 16384: 7178 1927092 268
allocb 65536: 152 79528 523
it looks like the call to physalloc is pretty pricey, but keeping the quicklist
makes that irrelevant in the steady state.
as to counts bigger than 64k, this is not allowed. allocb will just panic.
- erik
