[PATCH mptcp-next] mptcp: use fast lock for subflows when possible.

[PATCH mptcp-next] mptcp: use fast lock for subflows when possible.

[Paolo Abeni]

There are a bunch of callsite where the ssk socket
lock is acquired using the full-blown version eligible for
the fast variant. Let's move to the latter.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
The previous patch demonstrated that using lock_sock()
were the fast version is available can have worse side-effect
than slower performances.

This tries to address the topic.
---
 net/mptcp/pm_netlink.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 09722598994d..d4732a4f223e 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -540,6 +540,7 @@ void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk)
 	subflow = list_first_entry_or_null(&msk->conn_list, typeof(*subflow), node);
 	if (subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow;
 
 		spin_unlock_bh(&msk->pm.lock);
 		pr_debug("send ack for %s%s%s",
@@ -547,9 +548,9 @@ void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk)
 			 mptcp_pm_should_add_signal_ipv6(msk) ? " [ipv6]" : "",
 			 mptcp_pm_should_add_signal_port(msk) ? " [port]" : "");
 
-		lock_sock(ssk);
+		slow = lock_sock_fast(ssk);
 		tcp_send_ack(ssk);
-		release_sock(ssk);
+		unlock_sock_fast(ssk, slow);
 		spin_lock_bh(&msk->pm.lock);
 	}
 }
@@ -566,6 +567,7 @@ int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 		struct sock *sk = (struct sock *)msk;
 		struct mptcp_addr_info local;
+		bool slow;
 
 		local_address((struct sock_common *)ssk, &local);
 		if (!addresses_equal(&local, addr, addr->port))
@@ -578,9 +580,9 @@ int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
 
 		spin_unlock_bh(&msk->pm.lock);
 		pr_debug("send ack for mp_prio");
-		lock_sock(ssk);
+		slow = lock_sock_fast(ssk);
 		tcp_send_ack(ssk);
-		release_sock(ssk);
+		unlock_sock_fast(ssk, slow);
 		spin_lock_bh(&msk->pm.lock);
 
 		return 0;
-- 
2.26.3

Re: [PATCH mptcp-next] mptcp: use fast lock for subflows when possible.

[Mat Martineau]

On Wed, 26 May 2021, Paolo Abeni wrote:

> There are a bunch of callsite where the ssk socket
> lock is acquired using the full-blown version eligible for
> the fast variant. Let's move to the latter.
>
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> The previous patch demonstrated that using lock_sock()
> were the fast version is available can have worse side-effect
> than slower performances.
>
> This tries to address the topic.
> ---
> net/mptcp/pm_netlink.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)

Looks good to me, thanks Paolo.

Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>

-Mat


>
> diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
> index 09722598994d..d4732a4f223e 100644
> --- a/net/mptcp/pm_netlink.c
> +++ b/net/mptcp/pm_netlink.c
> @@ -540,6 +540,7 @@ void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk)
> 	subflow = list_first_entry_or_null(&msk->conn_list, typeof(*subflow), node);
> 	if (subflow) {
> 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
> +		bool slow;
>
> 		spin_unlock_bh(&msk->pm.lock);
> 		pr_debug("send ack for %s%s%s",
> @@ -547,9 +548,9 @@ void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk)
> 			 mptcp_pm_should_add_signal_ipv6(msk) ? " [ipv6]" : "",
> 			 mptcp_pm_should_add_signal_port(msk) ? " [port]" : "");
>
> -		lock_sock(ssk);
> +		slow = lock_sock_fast(ssk);
> 		tcp_send_ack(ssk);
> -		release_sock(ssk);
> +		unlock_sock_fast(ssk, slow);
> 		spin_lock_bh(&msk->pm.lock);
> 	}
> }
> @@ -566,6 +567,7 @@ int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
> 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
> 		struct sock *sk = (struct sock *)msk;
> 		struct mptcp_addr_info local;
> +		bool slow;
>
> 		local_address((struct sock_common *)ssk, &local);
> 		if (!addresses_equal(&local, addr, addr->port))
> @@ -578,9 +580,9 @@ int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
>
> 		spin_unlock_bh(&msk->pm.lock);
> 		pr_debug("send ack for mp_prio");
> -		lock_sock(ssk);
> +		slow = lock_sock_fast(ssk);
> 		tcp_send_ack(ssk);
> -		release_sock(ssk);
> +		unlock_sock_fast(ssk, slow);
> 		spin_lock_bh(&msk->pm.lock);
>
> 		return 0;
> -- 
> 2.26.3
>
>
>

--
Mat Martineau
Intel

Re: [PATCH mptcp-next] mptcp: use fast lock for subflows when possible.

[Paolo Abeni]

On Wed, 2021-05-26 at 21:19 -0700, Mat Martineau wrote:
> On Wed, 26 May 2021, Paolo Abeni wrote:
> 
> > There are a bunch of callsite where the ssk socket
> > lock is acquired using the full-blown version eligible for
> > the fast variant. Let's move to the latter.
> > 
> > Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> > ---
> > The previous patch demonstrated that using lock_sock()
> > were the fast version is available can have worse side-effect
> > than slower performances.
> > 
> > This tries to address the topic.
> > ---
> > net/mptcp/pm_netlink.c | 10 ++++++----
> > 1 file changed, 6 insertions(+), 4 deletions(-)
> 
> Looks good to me, thanks Paolo.
> 
> Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>

I'm sorry, this get mangled, some more needed chunk slipped in another
local patch. I'll send a v2 with more fast_lock()

/P