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| author |   Jarek Poplawski <jarkao2@gmail.com> | 2009-07-14 08:33:08 +0000 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2009-07-20 07:39:25 -0700 |
| commit | c3059477fce2d956a0bb3e04357324780c5d8eeb (patch) | |
| tree | c08cd660873667268132d556c2b66d7f9725a173 /net/ipv4/fib_trie.c | |
| parent | vlan: Propagate physical MTU changes (diff) | |
| download | linux-dev-c3059477fce2d956a0bb3e04357324780c5d8eeb.tar.xz linux-dev-c3059477fce2d956a0bb3e04357324780c5d8eeb.zip | |
ipv4: Use synchronize_rcu() during trie_rebalance()
During trie_rebalance() we free memory after resizing with call_rcu(),
but large updates, especially with PREEMPT_NONE configs, can cause
memory stresses, so this patch calls synchronize_rcu() in
tnode_free_flush() after each sync_pages to guarantee such freeing
(especially before resizing the root node).
The value of sync_pages = 128 is based on Pawel Staszewski's tests as
the lowest which doesn't hinder updating times. (For testing purposes
there was a sysfs module parameter to change it on demand, but it's
removed until we're sure it could be really useful.)
The patch is based on suggestions by: Paul E. McKenney
<paulmck@linux.vnet.ibm.com>
Reported-by: Pawel Staszewski <pstaszewski@itcare.pl>
Tested-by: Pawel Staszewski <pstaszewski@itcare.pl>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/fib_trie.c')
| -rw-r--r-- | net/ipv4/fib_trie.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index 63c2fa7b68c4..58ba9f4f2c92 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -164,6 +164,14 @@ static struct tnode *inflate(struct trie *t, struct tnode *tn); static struct tnode *halve(struct trie *t, struct tnode *tn); /* tnodes to free after resize(); protected by RTNL */ static struct tnode *tnode_free_head; +static size_t tnode_free_size; + +/* + * synchronize_rcu after call_rcu for that many pages; it should be especially + * useful before resizing the root node with PREEMPT_NONE configs; the value was + * obtained experimentally, aiming to avoid visible slowdown. + */ +static const int sync_pages = 128; static struct kmem_cache *fn_alias_kmem __read_mostly; static struct kmem_cache *trie_leaf_kmem __read_mostly; @@ -393,6 +401,8 @@ static void tnode_free_safe(struct tnode *tn) BUG_ON(IS_LEAF(tn)); tn->tnode_free = tnode_free_head; tnode_free_head = tn; + tnode_free_size += sizeof(struct tnode) + + (sizeof(struct node *) << tn->bits); } static void tnode_free_flush(void) @@ -404,6 +414,11 @@ static void tnode_free_flush(void) tn->tnode_free = NULL; tnode_free(tn); } + + if (tnode_free_size >= PAGE_SIZE * sync_pages) { + tnode_free_size = 0; + synchronize_rcu(); + } } static struct leaf *leaf_new(void) |