The patch titled
dcache: avoid RCU for never-hashed dentries
has been added to the -mm tree. Its filename is
dcache-avoid-rcu-for-never-hashed-dentries.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: dcache: avoid RCU for never-hashed dentries
From: Eric Dumazet <dada1@xxxxxxxxxxxxx>
Some dentries don't need to be globally visible in dentry hashtable.
(pipes & sockets)
Such dentries dont need to wait for a RCU grace period at delete time.
Being able to free them permits a better CPU cache use (hot cache)
This patch combined with (dont insert pipe dentries into dentry_hashtable)
reduced time of { pipe(p); close(p[0]); close(p[1]);} on my UP machine (1.6
GHz Pentium-M) from 3.23 us to 2.86 us (But this patch does not depend on
other patches, only bench results)
Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
fs/dcache.c | 16 ++++++++++++----
1 files changed, 12 insertions(+), 4 deletions(-)
diff -puN fs/dcache.c~dcache-avoid-rcu-for-never-hashed-dentries fs/dcache.c
--- a/fs/dcache.c~dcache-avoid-rcu-for-never-hashed-dentries
+++ a/fs/dcache.c
@@ -68,15 +68,19 @@ struct dentry_stat_t dentry_stat = {
.age_limit = 45,
};
-static void d_callback(struct rcu_head *head)
+static void __d_free(struct dentry *dentry)
{
- struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
-
if (dname_external(dentry))
kfree(dentry->d_name.name);
kmem_cache_free(dentry_cache, dentry);
}
+static void d_callback(struct rcu_head *head)
+{
+ struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
+ __d_free(dentry);
+}
+
/*
* no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry
* inside dcache_lock.
@@ -85,7 +89,11 @@ static void d_free(struct dentry *dentry
{
if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
- call_rcu(&dentry->d_u.d_rcu, d_callback);
+ /* if dentry was never inserted into hash, immediate free is OK */
+ if (dentry->d_hash.pprev == NULL)
+ __d_free(dentry);
+ else
+ call_rcu(&dentry->d_u.d_rcu, d_callback);
}
/*
_
Patches currently in -mm which might be from dada1@xxxxxxxxxxxxx are
git-net.patch
rcu-add-a-prefetch-in-rcu_do_batch.patch
dont-insert-pipe-dentries-into-dentry_hashtable.patch
dcache-avoid-rcu-for-never-hashed-dentries.patch
-
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