From patchwork Fri Jan 21 23:12:58 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 12720331 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29D21C433EF for ; Fri, 21 Jan 2022 23:13:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229604AbiAUXNE (ORCPT ); Fri, 21 Jan 2022 18:13:04 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:41554 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229555AbiAUXND (ORCPT ); Fri, 21 Jan 2022 18:13:03 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1642806782; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=38CLyOOFGNpsCH2Hm5Xzqz1LpA2MMoJHumLXa5e8yw0=; b=QnhfbvZqvJut7xASbRinIInUHhFgX5705sLsK/XbAUpXTXLGX1O0UbJ69ZZ7lQAoBf+Vvs xBLmLdN2cNjxpDaSkvgruP+5VXYgoqkodeBgchBDUpy0Mjx7kV51a8jy2RtULN90PkdCuD ERy7EXKTSAVEXC80oKfJ26fgBF78fTc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-632-PCfsLRkTMk60m92azzUROQ-1; Fri, 21 Jan 2022 18:13:01 -0500 X-MC-Unique: PCfsLRkTMk60m92azzUROQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 97EAB8143E5; Fri, 21 Jan 2022 23:13:00 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.33.36.5]) by smtp.corp.redhat.com (Postfix) with ESMTP id 876F9108AD; Fri, 21 Jan 2022 23:12:59 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH net] rxrpc: Adjust retransmission backoff From: David Howells To: netdev@vger.kernel.org Cc: Marc Dionne , Marc Dionne , Marc Dionne , linux-afs@lists.infradead.org, dhowells@redhat.com, linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org Date: Fri, 21 Jan 2022 23:12:58 +0000 Message-ID: <164280677857.1397447.9028458701099013997.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org Improve retransmission backoff by only backing off when we retransmit data packets rather than when we set the lost ack timer. To this end: (1) In rxrpc_resend(), use rxrpc_get_rto_backoff() when setting the retransmission timer and only tell it that we are retransmitting if we actually have things to retransmit. Note that it's possible for the retransmission algorithm to race with the processing of a received ACK, so we may see no packets needing retransmission. (2) In rxrpc_send_data_packet(), don't bump the backoff when setting the ack_lost_at timer, as it may then get bumped twice. With this, when looking at one particular packet, the retransmission intervals were seen to be 1.5ms, 2ms, 3ms, 5ms, 9ms, 17ms, 33ms, 71ms, 136ms, 264ms, 544ms, 1.088s, 2.1s, 4.2s and 8.3s. Fixes: c410bf01933e ("rxrpc: Fix the excessive initial retransmission timeout") Suggested-by: Marc Dionne Signed-off-by: David Howells Reviewed-by: Marc Dionne Tested-by: Marc Dionne cc: linux-afs@lists.infradead.org Link: https://lore.kernel.org/r/164138117069.2023386.17446904856843997127.stgit@warthog.procyon.org.uk/ --- net/rxrpc/call_event.c | 8 +++----- net/rxrpc/output.c | 2 +- 2 files changed, 4 insertions(+), 6 deletions(-) diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c index 6be2672a65ea..df864e692267 100644 --- a/net/rxrpc/call_event.c +++ b/net/rxrpc/call_event.c @@ -157,7 +157,7 @@ static void rxrpc_congestion_timeout(struct rxrpc_call *call) static void rxrpc_resend(struct rxrpc_call *call, unsigned long now_j) { struct sk_buff *skb; - unsigned long resend_at, rto_j; + unsigned long resend_at; rxrpc_seq_t cursor, seq, top; ktime_t now, max_age, oldest, ack_ts; int ix; @@ -165,10 +165,8 @@ static void rxrpc_resend(struct rxrpc_call *call, unsigned long now_j) _enter("{%d,%d}", call->tx_hard_ack, call->tx_top); - rto_j = call->peer->rto_j; - now = ktime_get_real(); - max_age = ktime_sub(now, jiffies_to_usecs(rto_j)); + max_age = ktime_sub(now, jiffies_to_usecs(call->peer->rto_j)); spin_lock_bh(&call->lock); @@ -213,7 +211,7 @@ static void rxrpc_resend(struct rxrpc_call *call, unsigned long now_j) } resend_at = nsecs_to_jiffies(ktime_to_ns(ktime_sub(now, oldest))); - resend_at += jiffies + rto_j; + resend_at += jiffies + rxrpc_get_rto_backoff(call->peer, retrans); WRITE_ONCE(call->resend_at, resend_at); if (unacked) diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c index 10f2bf2e9068..a45c83f22236 100644 --- a/net/rxrpc/output.c +++ b/net/rxrpc/output.c @@ -468,7 +468,7 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct sk_buff *skb, if (call->peer->rtt_count > 1) { unsigned long nowj = jiffies, ack_lost_at; - ack_lost_at = rxrpc_get_rto_backoff(call->peer, retrans); + ack_lost_at = rxrpc_get_rto_backoff(call->peer, false); ack_lost_at += nowj; WRITE_ONCE(call->ack_lost_at, ack_lost_at); rxrpc_reduce_call_timer(call, ack_lost_at, nowj,