On Mon, 2017-11-06 at 10:28 +0800, Liu Yu wrote:
> From: Liu Yu <allanyu...@tencent.com>
>
> When a mount of processes connect to the same port at the same address
> simultaneously, they are likely getting the same bhash and therefore
> conflict with each other.
>
> The more the cpu number, the worse in this case.
>
> Use spin_trylock instead for this scene, which seems doesn't matter
> for common case.
>
> Signed-off-by: Liu Yu <allanyu...@tencent.com>
> ---
> net/ipv4/inet_hashtables.c | 6 +++++-
> 1 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
> index e7d15fb..cc11ec7 100644
> --- a/net/ipv4/inet_hashtables.c
> +++ b/net/ipv4/inet_hashtables.c
> @@ -581,13 +581,17 @@ int __inet_hash_connect(struct inet_timewait_death_row
> *death_row,
> other_parity_scan:
> port = low + offset;
> for (i = 0; i < remaining; i += 2, port += 2) {
> + int ret;
> +
> if (unlikely(port >= high))
> port -= remaining;
> if (inet_is_local_reserved_port(net, port))
> continue;
> head = &hinfo->bhash[inet_bhashfn(net, port,
> hinfo->bhash_size)];
> - spin_lock_bh(&head->lock);
> + ret = spin_trylock(&head->lock);
> + if (unlikely(!ret))
> + continue;
>
> /* Does not bother with rcv_saddr checks, because
> * the established check is already unique enough.
This is broken.
I am pretty sure you have not really tested this patch properly.
Chances are very high that a connect() will miss slots and wont succeed,
when table is almost full.
Performance is nice, but we actually need to allocate a 4-tuple in a
more deterministic fashion.
