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author | Eric Dumazet <dada1@cosmosbay.com> | 2005-09-06 15:18:16 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-09-07 16:57:41 -0700 |
commit | 3f4bb1f4199b7dc0c958447b1e4898980013b884 (patch) | |
tree | 3d8aacfc6b7bbf7b2d224ae10ca693c55c64739e /include/linux | |
parent | 0811bab24ff1eecab38110eda7ea7847db95c64e (diff) | |
download | blackbird-op-linux-3f4bb1f4199b7dc0c958447b1e4898980013b884.tar.gz blackbird-op-linux-3f4bb1f4199b7dc0c958447b1e4898980013b884.zip |
[PATCH] struct dentry: place d_hash close to d_parent and d_name to speedup lookups
dentry cache uses sophisticated RCU technology (and prefetching if
available) but touches 2 cache lines per dentry during hlist lookup.
This patch moves d_hash in the same cache line than d_parent and d_name
fields so that :
1) One cache line is needed instead of two.
2) the hlist_for_each_rcu() prefetching has a chance to bring all the
needed data in advance, not only the part that includes d_hash.next.
I also changed one old comment that was wrong for 64bits.
A further optimisation would be to separate dentry in two parts, one that
is mostly read, and one writen (d_count/d_lock) to avoid false sharing on
SMP/NUMA but this would need different field placement depending on 32bits
or 64bits platform.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/linux')
-rw-r--r-- | include/linux/dcache.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 50be290d24d2..ab04b4f9b0db 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -88,8 +88,9 @@ struct dentry { * negative */ /* * The next three fields are touched by __d_lookup. Place them here - * so they all fit in a 16-byte range, with 16-byte alignment. + * so they all fit in a cache line. */ + struct hlist_node d_hash; /* lookup hash list */ struct dentry *d_parent; /* parent directory */ struct qstr d_name; @@ -103,7 +104,6 @@ struct dentry { void *d_fsdata; /* fs-specific data */ struct rcu_head d_rcu; struct dcookie_struct *d_cookie; /* cookie, if any */ - struct hlist_node d_hash; /* lookup hash list */ int d_mounted; unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */ }; |