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The current default size of the nullfs hash table used to lookup the

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existing nullfs vnode by the lower vnode is only 16 slots.  Since the
default mode for the nullfs is to cache the vnodes, hash has extremely
huge chains.

Size the nullfs hashtbl based on the current value of
desiredvnodes. Use vfs_hash_index() to calculate the hash bucket for a
given vnode.

Pointy hat to:	    kib
Diagnosed and reviewed by:	peter
Tested by:    peter, pho (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	5 days
This commit is contained in:
Konstantin Belousov 2013-01-14 05:44:47 +00:00
parent a41df84820
commit 603f963e56
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=245408
1 changed files with 6 additions and 10 deletions
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16
sys/fs/nullfs/null_subr.c
View file

@ -46,9 +46,6 @@
#include <fs/nullfs/null.h>
#define LOG2_SIZEVNODE 8 /* log2(sizeof struct vnode) */
#define NNULLNODECACHE 16
/*
* Null layer cache:
* Each cache entry holds a reference to the lower vnode
@ -57,12 +54,11 @@
* alias is removed the lower vnode is vrele'd.
*/
#define NULL_NHASH(vp) \
(&null_node_hashtbl[(((uintptr_t)vp)>>LOG2_SIZEVNODE) & null_node_hash])
#define NULL_NHASH(vp) (&null_node_hashtbl[vfs_hash_index(vp) & null_hash_mask])
static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
static u_long null_node_hash;
struct mtx null_hashmtx;
static struct mtx null_hashmtx;
static u_long null_hash_mask;
static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table");
MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part");
@ -77,8 +73,8 @@ nullfs_init(vfsp)
struct vfsconf *vfsp;
{
NULLFSDEBUG("nullfs_init\n"); /* printed during system boot */
null_node_hashtbl = hashinit(NNULLNODECACHE, M_NULLFSHASH, &null_node_hash);
null_node_hashtbl = hashinit(desiredvnodes, M_NULLFSHASH,
&null_hash_mask);
mtx_init(&null_hashmtx, "nullhs", NULL, MTX_DEF);
return (0);
}
@ -89,7 +85,7 @@ nullfs_uninit(vfsp)
{
mtx_destroy(&null_hashmtx);
hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_node_hash);
hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_hash_mask);
return (0);
}