kern/145246: [ufs] dirhash in 7.3 gratuitously frees hashes when it shouldn't [regression]

[Martin Birgmeier]

The following reply was made to PR kern/145246; it has been noted by GNATS.

From: Martin Birgmeier <Martin.Birgmeier at aon.at>
To: bug-followup at FreeBSD.org
Cc:  
Subject: Re: kern/145246: [ufs] dirhash in 7.3 gratuitously frees hashes when
 it shouldn't [regression]
Date: Thu, 01 Apr 2010 16:54:13 +0200

 I believe that there should be some notion of "value" given to resources 
 which may potentially be destroyed and recreated - computing the dirhash 
 takes a lot of time (see 
 http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/117954 ), and this work 
 should not be thrown away lightly. (This is why dirhash exists in the 
 first place.)
 
 Maybe the lowmem handler could be modified to only use the dirhash 
 lowmem handler as a last resort. In my case, the kernel did not really 
 seem to be that short on memory, as it has now been running with 
 moderate to high load for 24 hours with the reversion to SVN rev 195783 
 for ufs_dirhash.c and dirhash.h.
 
 I have configured vfs.ufs.dirhash_maxmem=33554432 (32M) by the way. 
 Compared to 1.25G, this is only 2.5%, so I believe not really something 
 that's eating lots of memory.
 
 Regards,
 
 Martin