From nobody Sat Oct 22 10:14:25 2022 X-Original-To: freebsd-net@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4MvcdW3xLCz4gbtv for ; Sat, 22 Oct 2022 10:14:39 +0000 (UTC) (envelope-from hps@selasky.org) Received: from mail.turbocat.net (turbocat.net [IPv6:2a01:4f8:c17:6c4b::2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4MvcdV1jPFz3SWR for ; Sat, 22 Oct 2022 10:14:37 +0000 (UTC) (envelope-from hps@selasky.org) Received: from [10.36.2.68] (unknown [178.232.223.95]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mail.turbocat.net (Postfix) with ESMTPSA id B000826077A; Sat, 22 Oct 2022 12:14:29 +0200 (CEST) Message-ID: <1ed66217-5463-fd4d-7e7a-58d9981bc44c@selasky.org> Date: Sat, 22 Oct 2022 12:14:25 +0200 List-Id: Networking and TCP/IP with FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-net List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-net@freebsd.org MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:102.0) Gecko/20100101 Thunderbird/102.3.0 Subject: Re: Too aggressive TCP ACKs To: Zhenlei Huang , Michael Tuexen Cc: freebsd-net@freebsd.org References: <75D35F36-7759-4168-ADBA-C2414F5B53BC@gmail.com> <712641B3-5196-40CC-9B64-04637F16F649@lurchi.franken.de> <62A0DD30-B3ED-48BE-9C01-146487599092@gmail.com> <0FED34A9-D093-442A-83B7-08C06D11F8B5@lurchi.franken.de> <330A9146-F7CC-4CAB-9003-2F90B872AC3E@gmail.com> Content-Language: en-US From: Hans Petter Selasky In-Reply-To: <330A9146-F7CC-4CAB-9003-2F90B872AC3E@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4MvcdV1jPFz3SWR X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of hps@selasky.org designates 2a01:4f8:c17:6c4b::2 as permitted sender) smtp.mailfrom=hps@selasky.org X-Spamd-Result: default: False [-3.30 / 15.00]; NEURAL_HAM_SHORT(-1.00)[-0.999]; NEURAL_HAM_MEDIUM(-1.00)[-0.999]; NEURAL_HAM_LONG(-1.00)[-0.999]; R_SPF_ALLOW(-0.20)[+a:mail.turbocat.net]; MIME_GOOD(-0.10)[text/plain]; MLMMJ_DEST(0.00)[freebsd-net@freebsd.org]; FREEMAIL_TO(0.00)[gmail.com,lurchi.franken.de]; R_DKIM_NA(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; ASN(0.00)[asn:24940, ipnet:2a01:4f8::/32, country:DE]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; DMARC_NA(0.00)[selasky.org]; MID_RHS_MATCH_FROM(0.00)[]; ARC_NA(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; TAGGED_RCPT(0.00)[]; RCVD_TLS_ALL(0.00)[] X-ThisMailContainsUnwantedMimeParts: N Hi, Some thoughts about this topic. Delaying ACKs means loss of performance when using Gigabit TCP connections in data centers. There it is important to ACK the data as quick as possible, to avoid running out of TCP window space. Thinking about TCP connections at 30 GBit/s and above! I think the implementation should be exactly like it is. There is a software LRO in FreeBSD to coalesce the ACKs before they hit the network stack, so there are no real problems there. --HPS