From patchwork Thu Apr 7 07:52:40 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Artem Savkov X-Patchwork-Id: 12804612 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 31EA1C433F5 for ; Thu, 7 Apr 2022 07:53:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242340AbiDGHy5 (ORCPT ); Thu, 7 Apr 2022 03:54:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39192 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242323AbiDGHyy (ORCPT ); Thu, 7 Apr 2022 03:54:54 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id CFC8F1C42D9 for ; Thu, 7 Apr 2022 00:52:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1649317975; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ioK6OvofKyIpy+vHQcfZR1zFpndRrQMZLUPba8CRcNw=; b=El9GrOm5iKQFBCior3ofya21rKyTrUfVQUdYOu8SU/blKittPt5vGwjrK2+b9+2Ki7F103 hLYTva3SwQzmnEUlqMGnH0V9Hz+fJHftoroHR+W3KQzJncZyutwB+Q+NkL1eVOIBSvRA0G wV4Kj8kM1H+2OBDU+XaPYV0gscPB3cM= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-52-yDek7xRGOhKsMC1QW0IqbQ-1; Thu, 07 Apr 2022 03:52:51 -0400 X-MC-Unique: yDek7xRGOhKsMC1QW0IqbQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6DC06380409B; Thu, 7 Apr 2022 07:52:51 +0000 (UTC) Received: from shodan.usersys.redhat.com (unknown [10.43.17.22]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 25E271121330; Thu, 7 Apr 2022 07:52:45 +0000 (UTC) Received: by shodan.usersys.redhat.com (Postfix, from userid 1000) id DC12B1C00FD; Thu, 7 Apr 2022 09:52:43 +0200 (CEST) From: Artem Savkov To: Thomas Gleixner , Josh Poimboeuf , Anna-Maria Behnsen , netdev@vger.kernel.org Cc: davem@davemloft.net, yoshfuji@linux-ipv6.org, dsahern@kernel.org, linux-kernel@vger.kernel.org, Artem Savkov Subject: [PATCH v4 0/2] Upper bound kernel timers Date: Thu, 7 Apr 2022 09:52:40 +0200 Message-Id: <20220407075242.118253-1-asavkov@redhat.com> In-Reply-To: <871qyb35q4.ffs@tglx> References: <871qyb35q4.ffs@tglx> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org As previously discussed [1] we had a report of a regression in TCP keepalive timer where timers were up to 4 minutes late resulting in disconnects. This patchset tries to fix the problem by introducing upper bound kernel timers and making tcp keepalive timer use those. [1] https://lore.kernel.org/all/20210302001054.4qgrvnkltvkgikzr@treble/T/#u --- Changes in v4: - Drop any attempts to be smart when calculating timer adjustment and always substract LVL_GRAN so that base clock lag won't be such a problem. This means that in some cases we will always be early, but all we want is not to be late. Changes in v3: - A different approach: instead of introducing upper bound timers try to account for timer wheen granularity on timer (re)arming step. - Not sure whether moving lvl calculation into a separate function is worth it. - Had a hard time naming the upper_bount_timeout() function - any suggestions welcome. Changes in v2: - TIMER_UPPER_BOUND flag description added as a comment in timer.h - Code style fixes - More elaborate commit message in timer commit Artem Savkov (2): timer: add a function to adjust timeouts to be upper bound net: make tcp keepalive timer upper bound include/linux/timer.h | 1 + kernel/time/timer.c | 68 ++++++++++++++++++++++++++------- net/ipv4/inet_connection_sock.c | 2 +- 3 files changed, 57 insertions(+), 14 deletions(-)