diff options
| author | Alexander Motin <[email protected]> | 2021-06-29 08:59:14 -0400 |
|---|---|---|
| committer | GitHub <[email protected]> | 2021-06-29 06:59:14 -0600 |
| commit | 5b7053a9a5a624603843a07ac0b360af64839e72 (patch) | |
| tree | 14f35686ae48cd8b876fc1a0741993e0a5c324d1 /module/zfs/dmu_objset.c | |
| parent | f20fb199e60722abc052b6034bddb6b83d870c99 (diff) | |
Avoid 64bit division in multilist index functions
The number of sublists in a multilist is relatively small. We dont need
64 bits to calculate an index. 32 bits is sufficient and makes the
code more efficient.
Reviewed-by: Matthew Ahrens <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Mark Maybee <[email protected]>
Signed-off-by: Alexander Motin <[email protected]>
Sponsored-By: iXsystems, Inc.
Closes #12288
Diffstat (limited to 'module/zfs/dmu_objset.c')
| -rw-r--r-- | module/zfs/dmu_objset.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c index 22deee7f3..af107fb8a 100644 --- a/module/zfs/dmu_objset.c +++ b/module/zfs/dmu_objset.c @@ -399,7 +399,15 @@ static unsigned int dnode_multilist_index_func(multilist_t *ml, void *obj) { dnode_t *dn = obj; - return (dnode_hash(dn->dn_objset, dn->dn_object) % + + /* + * The low order bits of the hash value are thought to be + * distributed evenly. Otherwise, in the case that the multilist + * has a power of two number of sublists, each sublists' usage + * would not be evenly distributed. In this context full 64bit + * division would be a waste of time, so limit it to 32 bits. + */ + return ((unsigned int)dnode_hash(dn->dn_objset, dn->dn_object) % multilist_get_num_sublists(ml)); } |