ZFS arc sizing (maybe related to kern/145229)

[Peter Schuller]

> check kstat.zfs.misc.arcstats.memory_throttle_count
> This counter is increased every time zfs thinks system is running low on
> memory and will force a write flush and reduce arc size to minimum. Biggest

It doesn't always seem to do so. I did (only) one test, and here is
some output from another little loop while I was dd:ing to a file at
maximum speed:

Thu Apr 8 22:13:38 CEST 2010: 1229.71 MB, 11 throttles
Thu Apr 8 22:13:39 CEST 2010: 1231.92 MB, 11 throttles
Thu Apr 8 22:13:40 CEST 2010: 1233.26 MB, 11 throttles
Thu Apr 8 22:13:42 CEST 2010: 1235.36 MB, 11 throttles
Thu Apr 8 22:13:43 CEST 2010: 1237.58 MB, 11 throttles
Thu Apr 8 22:13:44 CEST 2010: 1237.83 MB, 11 throttles
Thu Apr 8 22:13:45 CEST 2010: 1237.83 MB, 11 throttles
Thu Apr 8 22:13:46 CEST 2010: 1239.94 MB, 11 throttles
Thu Apr 8 22:13:47 CEST 2010: 1242.38 MB, 11 throttles
Thu Apr 8 22:13:48 CEST 2010: 1264.49 MB, 11 throttles
Thu Apr 8 22:13:50 CEST 2010: 1204.95 MB, 11 throttles
Thu Apr 8 22:13:51 CEST 2010: 1228.51 MB, 14 throttles
Thu Apr 8 22:13:52 CEST 2010: 1228.64 MB, 14 throttles
Thu Apr 8 22:13:53 CEST 2010: 1228.81 MB, 14 throttles
Thu Apr 8 22:13:54 CEST 2010: 1228.81 MB, 14 throttles
Thu Apr 8 22:13:55 CEST 2010: 1228.81 MB, 14 throttles
Thu Apr 8 22:13:56 CEST 2010: 1228.81 MB, 14 throttles
Thu Apr 8 22:13:58 CEST 2010: 1228.74 MB, 14 throttles
Thu Apr 8 22:13:59 CEST 2010: 1228.89 MB, 14 throttles
Thu Apr 8 22:14:00 CEST 2010: 1228.91 MB, 14 throttles
Thu Apr 8 22:14:03 CEST 2010: 1229.05 MB, 17 throttles
Thu Apr 8 22:14:07 CEST 2010: 1228.96 MB, 19 throttles
Thu Apr 8 22:14:16 CEST 2010: 1228.93 MB, 22 throttles
Thu Apr 8 22:14:18 CEST 2010: 1229.19 MB, 22 throttles
Thu Apr 8 22:14:19 CEST 2010: 1229.09 MB, 26 throttles
Thu Apr 8 22:14:25 CEST 2010: 1229.04 MB, 26 throttles
Thu Apr 8 22:14:30 CEST 2010: 1229.08 MB, 29 throttles
Thu Apr 8 22:14:32 CEST 2010: 1230.13 MB, 29 throttles
Thu Apr 8 22:14:36 CEST 2010: 1229.11 MB, 32 throttles
Thu Apr 8 22:14:40 CEST 2010: 1229.34 MB, 32 throttles
Thu Apr 8 22:14:44 CEST 2010: 1229.25 MB, 35 throttles
Thu Apr 8 22:14:46 CEST 2010: 1229.28 MB, 35 throttles
Thu Apr 8 22:14:50 CEST 2010: 1236.55 MB, 38 throttles
Thu Apr 8 22:14:52 CEST 2010: 1238.9 MB, 38 throttles
Thu Apr 8 22:14:53 CEST 2010: 1241 MB, 38 throttles


-- 
/ Peter Schuller