diff mbox series

[net,1/5] rxrpc: Fix congestion control algorithm

Message ID 20240503150749.1001323-2-dhowells@redhat.com (mailing list archive)
State Accepted
Commit ba4e103848d3a2a28a0445e39f4a9564187efe54
Delegated to: Netdev Maintainers
Headers show
Series rxrpc: Miscellaneous fixes | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 929 this patch: 929
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 7 of 7 maintainers
netdev/build_clang success Errors and warnings before: 937 this patch: 937
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 940 this patch: 940
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 30 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

David Howells May 3, 2024, 3:07 p.m. UTC 
Make the following fixes to the congestion control algorithm:

 (1) Don't vary the cwnd starting value by the size of RXRPC_TX_SMSS since
     that's currently held constant - set to the size of a jumbo subpacket
     payload so that we can create jumbo packets on the fly.  The current
     code invariably picks 3 as the starting value.

     Further, the starting cwnd needs to be an even number because we ack
     every other packet, so set it to 4.

 (2) Don't cut ssthresh when we see an ACK come from the peer with a
     receive window (rwind) less than ssthresh.  ssthresh keeps track of
     characteristics of the connection whereas rwind may be reduced by the
     peer for any reason - and may be reduced to 0.

Fixes: 1fc4fa2ac93d ("rxrpc: Fix congestion management")
Fixes: 0851115090a3 ("rxrpc: Reduce ssthresh to peer's receive window")
Signed-off-by: David Howells <dhowells@redhat.com>
Suggested-by: Simon Wilkinson <sxw@auristor.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org
---
 net/rxrpc/ar-internal.h | 2 +-
 net/rxrpc/call_object.c | 7 +------
 net/rxrpc/input.c       | 3 ---
 3 files changed, 2 insertions(+), 10 deletions(-)
diff mbox series

Patch

diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 08c0a32db8c7..08de24658f4f 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -697,7 +697,7 @@  struct rxrpc_call {
 	 * packets) rather than bytes.
 	 */
 #define RXRPC_TX_SMSS		RXRPC_JUMBO_DATALEN
-#define RXRPC_MIN_CWND		(RXRPC_TX_SMSS > 2190 ? 2 : RXRPC_TX_SMSS > 1095 ? 3 : 4)
+#define RXRPC_MIN_CWND		4
 	u8			cong_cwnd;	/* Congestion window size */
 	u8			cong_extra;	/* Extra to send for congestion management */
 	u8			cong_ssthresh;	/* Slow-start threshold */
diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index 01fa71e8b1f7..f9e983a12c14 100644
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -174,12 +174,7 @@  struct rxrpc_call *rxrpc_alloc_call(struct rxrpc_sock *rx, gfp_t gfp,
 	call->rx_winsize = rxrpc_rx_window_size;
 	call->tx_winsize = 16;
 
-	if (RXRPC_TX_SMSS > 2190)
-		call->cong_cwnd = 2;
-	else if (RXRPC_TX_SMSS > 1095)
-		call->cong_cwnd = 3;
-	else
-		call->cong_cwnd = 4;
+	call->cong_cwnd = RXRPC_MIN_CWND;
 	call->cong_ssthresh = RXRPC_TX_MAX_WINDOW;
 
 	call->rxnet = rxnet;
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 3dedb8c0618c..860075f1290b 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -685,9 +685,6 @@  static void rxrpc_input_ack_trailer(struct rxrpc_call *call, struct sk_buff *skb
 		call->tx_winsize = rwind;
 	}
 
-	if (call->cong_ssthresh > rwind)
-		call->cong_ssthresh = rwind;
-
 	mtu = min(ntohl(trailer->maxMTU), ntohl(trailer->ifMTU));
 
 	peer = call->peer;