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author | Eric Dumazet <eric.dumazet@gmail.com> | 2010-06-15 08:23:14 +0000 |
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committer | David S. Miller <davem@davemloft.net> | 2010-06-15 14:23:38 -0700 |
commit | aa1039e73cc2cf834e99c09d2033d5d2675357b9 (patch) | |
tree | 0db06e4adddaf0f77b4e8de170710b74a17375e4 /include/net/inetpeer.h | |
parent | 7b34a4644b4342896e0c1967b8f953213ea4a990 (diff) | |
download | linux-aa1039e73cc2cf834e99c09d2033d5d2675357b9.tar.gz linux-aa1039e73cc2cf834e99c09d2033d5d2675357b9.tar.bz2 linux-aa1039e73cc2cf834e99c09d2033d5d2675357b9.zip |
inetpeer: RCU conversion
inetpeer currently uses an AVL tree protected by an rwlock.
It's possible to make most lookups use RCU
1) Add a struct rcu_head to struct inet_peer
2) add a lookup_rcu_bh() helper to perform lockless and opportunistic
lookup. This is a normal function, not a macro like lookup().
3) Add a limit to number of links followed by lookup_rcu_bh(). This is
needed in case we fall in a loop.
4) add an smp_wmb() in link_to_pool() right before node insert.
5) make unlink_from_pool() use atomic_cmpxchg() to make sure it can take
last reference to an inet_peer, since lockless readers could increase
refcount, even while we hold peers.lock.
6) Delay struct inet_peer freeing after rcu grace period so that
lookup_rcu_bh() cannot crash.
7) inet_getpeer() first attempts lockless lookup.
Note this lookup can fail even if target is in AVL tree, but a
concurrent writer can let tree in a non correct form.
If this attemps fails, lock is taken a regular lookup is performed
again.
8) convert peers.lock from rwlock to a spinlock
9) Remove SLAB_HWCACHE_ALIGN when peer_cachep is created, because
rcu_head adds 16 bytes on 64bit arches, doubling effective size (64 ->
128 bytes)
In a future patch, this is probably possible to revert this part, if rcu
field is put in an union to share space with rid, ip_id_count, tcp_ts &
tcp_ts_stamp. These fields being manipulated only with refcnt > 0.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/inetpeer.h')
-rw-r--r-- | include/net/inetpeer.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h index 87b1df0d4d8c..617404730422 100644 --- a/include/net/inetpeer.h +++ b/include/net/inetpeer.h @@ -26,6 +26,7 @@ struct inet_peer { atomic_t ip_id_count; /* IP ID for the next packet */ __u32 tcp_ts; __u32 tcp_ts_stamp; + struct rcu_head rcu; }; void inet_initpeers(void) __init; |