Re: [PATCH net-2.6.25 1/3] Uninline the __inet_hash function

[Pavel Emelyanov <xemul@openvz.org>]

Eric Dumazet wrote:
> Pavel Emelyanov a écrit :
>> This one is used in quite many places in the networking code and
>> seems to big to be inline.
>>
>> After the patch net/ipv4/build-in.o loses 725 bytes:
>> add/remove: 1/0 grow/shrink: 0/5 up/down: 374/-1099 (-725)
>> function                                     old     new   delta
>> __inet_hash                                    -     374    +374
>> tcp_sacktag_write_queue                     2255    2254      -1
>> __inet_lookup_listener                       284     274     -10
>> tcp_v4_syn_recv_sock                         755     495    -260
>> tcp_v4_hash                                  389      40    -349
>> inet_hash_connect                           1165     686    -479
>>
>> Exporting this is for dccp module.
>>
>> Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
>>
>> ---
>>
>>  include/net/inet_hashtables.h |   27 ++-------------------------
>>  net/ipv4/inet_hashtables.c    |   27 +++++++++++++++++++++++++++
>>  2 files changed, 29 insertions(+), 25 deletions(-)
>>
>> diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
>> index 37f6cb1..1a43125 100644
>> --- a/include/net/inet_hashtables.h
>> +++ b/include/net/inet_hashtables.h
>> @@ -264,31 +264,8 @@ static inline void inet_listen_unlock(struct inet_hashinfo *hashinfo)
>>  		wake_up(&hashinfo->lhash_wait);
>>  }
>>  
>> -static inline void __inet_hash(struct inet_hashinfo *hashinfo,
>> -			       struct sock *sk, const int listen_possible)
>> -{
>> -	struct hlist_head *list;
>> -	rwlock_t *lock;
>> -
>> -	BUG_TRAP(sk_unhashed(sk));
>> -	if (listen_possible && sk->sk_state == TCP_LISTEN) {
>> -		list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
>> -		lock = &hashinfo->lhash_lock;
>> -		inet_listen_wlock(hashinfo);
>> -	} else {
>> -		struct inet_ehash_bucket *head;
>> -		sk->sk_hash = inet_sk_ehashfn(sk);
>> -		head = inet_ehash_bucket(hashinfo, sk->sk_hash);
>> -		list = &head->chain;
>> -		lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
>> -		write_lock(lock);
>> -	}
>> -	__sk_add_node(sk, list);
>> -	sock_prot_inc_use(sk->sk_prot);
>> -	write_unlock(lock);
>> -	if (listen_possible && sk->sk_state == TCP_LISTEN)
>> -		wake_up(&hashinfo->lhash_wait);
>> -}
>> +extern void __inet_hash(struct inet_hashinfo *hashinfo, struct sock *sk,
>> +		const int listen_possible);
>>  
>>  static inline void inet_hash(struct inet_hashinfo *hashinfo, struct sock *sk)
>>  {
>> diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
>> index 67704da..46f899b 100644
>> --- a/net/ipv4/inet_hashtables.c
>> +++ b/net/ipv4/inet_hashtables.c
>> @@ -267,6 +267,33 @@ static inline u32 inet_sk_port_offset(const struct sock *sk)
>>  					  inet->dport);
>>  }
>>  
>> +void __inet_hash(struct inet_hashinfo *hashinfo, struct sock *sk,
>> +		const int listen_possible)
>> +{
>> +	struct hlist_head *list;
>> +	rwlock_t *lock;
>> +
>> +	BUG_TRAP(sk_unhashed(sk));
>> +	if (listen_possible && sk->sk_state == TCP_LISTEN) {
>> +		list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
>> +		lock = &hashinfo->lhash_lock;
>> +		inet_listen_wlock(hashinfo);
>> +	} else {
>> +		struct inet_ehash_bucket *head;
>> +		sk->sk_hash = inet_sk_ehashfn(sk);
>> +		head = inet_ehash_bucket(hashinfo, sk->sk_hash);
>> +		list = &head->chain;
>> +		lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
>> +		write_lock(lock);
>> +	}
>> +	__sk_add_node(sk, list);
>> +	sock_prot_inc_use(sk->sk_prot);
>> +	write_unlock(lock);
>> +	if (listen_possible && sk->sk_state == TCP_LISTEN)
>> +		wake_up(&hashinfo->lhash_wait);
>> +}
>> +EXPORT_SYMBOL_GPL(__inet_hash);
>> +
>>  /*
>>   * Bind a port for a connect operation and hash it.
>>   */
> 
> If you un-inline this (good idea), I am not sure we still need listen_possible 
> argument.
> 
> It was usefull only to help compiler to zap dead code (since it was known at 
> compile time), now it only adds some extra test and argument passing.

Hm... I've tried to address this issue and got worse result - minus
600 bytes (vs minus 725). So, what would be more preferable - get a 
smaller code with one extra 'if' or get a bit larger code without it?

> Thank you

Thanks,
Pavel