mountd.c uses a single linked list of "struct exportlist" structures, where there is one of these for each exported file system on the NFS server. This list gets long if there are a large number of file systems exported and the list must be searched for each line in the exports file(s) when SIGHUP causes the exports file(s) to be reloaded. A simple benchmark that traverses SLIST() elements and compares two 32bit fields in the structure for equal (which is what the search is) appears to take a couple of nsec. So, for a server with 72000 exported file systems, this can take about 5sec during reload of the exports file(s). By replacing the single linked list with a hash table with a target of 10 elements per list, the time should be reduced to less than 1msec. Peter Errikson (who has a server with 72000+ exported file systems) ran a test program using 5 hashes to see how they worked. fnv_32_buf(fsid,..., 0) fnv_32_buf(fsid,..., FNV1_32_INIT) hash32_buf(fsid,..., 0) hash32_buf(fsid,..., HASHINIT) - plus simply using the low order bits of fsid.val[0]. The first three behaved about equally well, with the first one being slightly better than the others. It has an average variation of about 4.5% about the target list length and that is what this patch uses. Peter Errikson also tested this hash table version and found that the performance wasn't measurably improved by a larger hash table, so a load factor of 10 appears adequate. Tested by: pen@lysator.liu.se (with other patches) PR: 237860 MFC after: 1 month |
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bin | ||
cddl | ||
contrib | ||
crypto | ||
etc | ||
gnu | ||
include | ||
kerberos5 | ||
lib | ||
libexec | ||
release | ||
rescue | ||
sbin | ||
secure | ||
share | ||
stand | ||
sys | ||
targets | ||
tests | ||
tools | ||
usr.bin | ||
usr.sbin | ||
.arcconfig | ||
.arclint | ||
.cirrus.yml | ||
.gitattributes | ||
.gitignore | ||
COPYRIGHT | ||
LOCKS | ||
MAINTAINERS | ||
Makefile | ||
Makefile.inc1 | ||
Makefile.libcompat | ||
Makefile.sys.inc | ||
ObsoleteFiles.inc | ||
README | ||
README.md | ||
UPDATING |
FreeBSD Source:
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