After scouring the internet, it seems that no one else has done a great deal of testing of UFS2 dirhash defaults lately.
As the dirhash feature has effectively been tested for regressions, I would like to propose setting the default dirhash values to my original recommendation: vfs.ufs.dirhash_maxmem: 20971520 vfs.ufs.dirhash_reclaimage: 60 The last benchmarks from 2008 only tested dirhash_maxmem at 2 and 64 megs. I found in my testing that setting maxmem much over 32 megs makes the UFS dirhash dysfunctional, as scavenging 10% of maxmem on each vm_lowmem event becomes too aggressive. While autotuning defaults is highly desirable, autotuning dirhash_maxmem opens the can of worms of also tuning the hard coded 10% scavenging. It may be better to hard code the maxmem default. It may be appropriate to set the reclaimage to 5 minutes rather than 5 seconds; I consider 60 seconds to still be a very conservative value, but at least an effective one. -- View this message in context: http://freebsd.1045724.n5.nabble.com/Suggest-changing-dirhash-defaults-for-FreeBSD-9-2-tp5839351p5840115.html Sent from the freebsd-stable mailing list archive at Nabble.com. _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[email protected]"
