linux-kernel - [PATCH net-next 24/37] rxrpc: Generate rtt

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Message-ID: <20241202143057.378147-25-dhowells@redhat.com>
Date: Mon,  2 Dec 2024 14:30:42 +0000
From: David Howells <dhowells@...hat.com>
To: netdev@...r.kernel.org
Cc: David Howells <dhowells@...hat.com>,
	Marc Dionne <marc.dionne@...istor.com>,
	Yunsheng Lin <linyunsheng@...wei.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	linux-afs@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH net-next 24/37] rxrpc: Generate rtt_min

Generate rtt_min as this is required by RACK-TLP.

Signed-off-by: David Howells <dhowells@...hat.com>
cc: Marc Dionne <marc.dionne@...istor.com>
cc: "David S. Miller" <davem@...emloft.net>
cc: Eric Dumazet <edumazet@...gle.com>
cc: Jakub Kicinski <kuba@...nel.org>
cc: Paolo Abeni <pabeni@...hat.com>
cc: linux-afs@...ts.infradead.org
cc: netdev@...r.kernel.org
---
 lib/win_minmax.c        |  1 +
 net/rxrpc/ar-internal.h |  2 ++
 net/rxrpc/rtt.c         | 20 ++++++++++++++++----
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/lib/win_minmax.c b/lib/win_minmax.c
index ec10506834b6..1682e614309c 100644
--- a/lib/win_minmax.c
+++ b/lib/win_minmax.c
@@ -97,3 +97,4 @@ u32 minmax_running_min(struct minmax *m, u32 win, u32 t, u32 meas)
 
 	return minmax_subwin_update(m, win, &val);
 }
+EXPORT_SYMBOL(minmax_running_min);
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index e68d0ecc4866..012b9bc283eb 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -371,6 +371,8 @@ struct rxrpc_peer {
 	spinlock_t		rtt_input_lock;	/* RTT lock for input routine */
 	ktime_t			rtt_last_req;	/* Time of last RTT request */
 	unsigned int		rtt_count;	/* Number of samples we've got */
+	unsigned int		rtt_taken;	/* Number of samples taken (wrapping) */
+	struct minmax		min_rtt;	/* Estimated minimum RTT */
 
 	u32			srtt_us;	/* smoothed round trip time << 3 in usecs */
 	u32			mdev_us;	/* medium deviation			*/
diff --git a/net/rxrpc/rtt.c b/net/rxrpc/rtt.c
index 6dc51486b5a6..8048467f4bee 100644
--- a/net/rxrpc/rtt.c
+++ b/net/rxrpc/rtt.c
@@ -127,16 +127,27 @@ static void rxrpc_set_rto(struct rxrpc_peer *peer)
 	peer->rto_us = rxrpc_bound_rto(rto);
 }
 
-static void rxrpc_ack_update_rtt(struct rxrpc_peer *peer, long rtt_us)
+static void rxrpc_update_rtt_min(struct rxrpc_peer *peer, ktime_t resp_time, long rtt_us)
+{
+	/* Window size 5mins in approx usec (ipv4.sysctl_tcp_min_rtt_wlen) */
+	u32 wlen_us = 5ULL * NSEC_PER_SEC / 1024;
+
+	minmax_running_min(&peer->min_rtt, wlen_us, resp_time / 1024,
+			   (u32)rtt_us ? : jiffies_to_usecs(1));
+}
+
+static void rxrpc_ack_update_rtt(struct rxrpc_peer *peer, ktime_t resp_time, long rtt_us)
 {
 	if (rtt_us < 0)
 		return;
 
-	//rxrpc_update_rtt_min(peer, rtt_us);
+	/* Update RACK min RTT [RFC8985 6.1 Step 1]. */
+	rxrpc_update_rtt_min(peer, resp_time, rtt_us);
+
 	rxrpc_rtt_estimator(peer, rtt_us);
 	rxrpc_set_rto(peer);
 
-	/* RFC6298: only reset backoff on valid RTT measurement. */
+	/* Only reset backoff on valid RTT measurement [RFC6298]. */
 	peer->backoff = 0;
 }
 
@@ -157,9 +168,10 @@ void rxrpc_peer_add_rtt(struct rxrpc_call *call, enum rxrpc_rtt_rx_trace why,
 		return;
 
 	spin_lock(&peer->rtt_input_lock);
-	rxrpc_ack_update_rtt(peer, rtt_us);
+	rxrpc_ack_update_rtt(peer, resp_time, rtt_us);
 	if (peer->rtt_count < 3)
 		peer->rtt_count++;
+	peer->rtt_taken++;
 	spin_unlock(&peer->rtt_input_lock);
 
 	trace_rxrpc_rtt_rx(call, why, rtt_slot, send_serial, resp_serial,