From nobody Wed Oct 26 08:57:11 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 4My2kS0NvYz4gRQN for ; Wed, 26 Oct 2022 08:57:20 +0000 (UTC) (envelope-from thj@freebsd.org) Received: from wout2-smtp.messagingengine.com (wout2-smtp.messagingengine.com [64.147.123.25]) (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 4My2kR2BQbz3jfx for ; Wed, 26 Oct 2022 08:57:19 +0000 (UTC) (envelope-from thj@freebsd.org) Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailout.west.internal (Postfix) with ESMTP id 7C89532007F1; Wed, 26 Oct 2022 04:57:17 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute3.internal (MEProxy); Wed, 26 Oct 2022 04:57:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:date:date:feedback-id :feedback-id:from:from:in-reply-to:in-reply-to:message-id :mime-version:references:reply-to:sender:subject:subject:to:to :x-me-proxy:x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s= fm3; t=1666774637; x=1666861037; bh=JfPTkCPpljSlXuyvXzerqq2yHFNL mEMCAe2Mau6BDmg=; b=rufkUxKV4++JTOLFtJ2o+ClG8DNsUulHc8jb7mUeTe0m KF3c9ZC9PPb8qdNhIRp6cQcNY+EUY9L8seIN7W0PoJIcTesMTO974/zv0sU3Ndvn hIZJrKAb9paJrBzR/49ke+Af4NOxCnhJZ5N084cUFj0mQWJAAgvApWciSgRlobz6 luUP3P3tb2RLNwWQJbxiS/sbv6bNlzN70xsOViN3lRfgKhlAH5BqVLWERjZXO88t /EQ+cwXNeFEbgR40jM/94JaWrECQnzah8mkcbZgOYFYfSwEvMz2DZivBnxGyipz5 ox7Bs/z1EX7p5/wFNLmTq8QrCY+DgGQ5CrihuX6stA== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvgedrtddvgddutdcutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenuc fjughrpeffhffvvefukfhfgggtuggjsehttdertddttddvnecuhfhrohhmpefvohhmucfl ohhnvghsuceothhhjhesfhhrvggvsghsugdrohhrgheqnecuggftrfgrthhtvghrnhepje elfeduiedvveffveeukeekffffveeiudejkeeuleeihfeludeuieeuvefhfeejnecuffho mhgrihhnpeifihhlvgihrdgtohhmnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrg hmpehmrghilhhfrhhomhepthhhjhesfhhrvggvsghsugdrohhrgh X-ME-Proxy: Feedback-ID: ib75146ab:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Wed, 26 Oct 2022 04:57:15 -0400 (EDT) Date: Wed, 26 Oct 2022 09:57:11 +0100 From: Tom Jones To: Hans Petter Selasky Cc: Zhenlei Huang , Michael Tuexen , freebsd-net@freebsd.org Subject: Re: Too aggressive TCP ACKs Message-ID: 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> <1ed66217-5463-fd4d-7e7a-58d9981bc44c@selasky.org> 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 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1ed66217-5463-fd4d-7e7a-58d9981bc44c@selasky.org> X-Rspamd-Queue-Id: 4My2kR2BQbz3jfx X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=messagingengine.com header.s=fm3 header.b=rufkUxKV; dmarc=none; spf=softfail (mx1.freebsd.org: 64.147.123.25 is neither permitted nor denied by domain of thj@freebsd.org) smtp.mailfrom=thj@freebsd.org X-Spamd-Result: default: False [-2.40 / 15.00]; SUSPICIOUS_RECIPS(1.50)[]; DWL_DNSWL_LOW(-1.00)[messagingengine.com:dkim]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; NEURAL_HAM_SHORT(-1.00)[-0.999]; NEURAL_HAM_LONG(-1.00)[-0.996]; MID_RHS_NOT_FQDN(0.50)[]; R_DKIM_ALLOW(-0.20)[messagingengine.com:s=fm3]; RCVD_IN_DNSWL_LOW(-0.10)[64.147.123.25:from]; MIME_GOOD(-0.10)[text/plain]; MIME_TRACE(0.00)[0:+]; DMARC_NA(0.00)[freebsd.org]; R_SPF_SOFTFAIL(0.00)[~all]; TAGGED_RCPT(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RWL_MAILSPIKE_POSSIBLE(0.00)[64.147.123.25:from]; MLMMJ_DEST(0.00)[freebsd-net@freebsd.org]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_THREE(0.00)[4]; FROM_HAS_DN(0.00)[]; ASN(0.00)[asn:29838, ipnet:64.147.123.0/24, country:US]; RCVD_TLS_LAST(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; ARC_NA(0.00)[]; FREEMAIL_CC(0.00)[gmail.com,lurchi.franken.de,freebsd.org]; DKIM_TRACE(0.00)[messagingengine.com:+]; FREEFALL_USER(0.00)[thj]; RCVD_VIA_SMTP_AUTH(0.00)[] X-ThisMailContainsUnwantedMimeParts: N On Sat, Oct 22, 2022 at 12:14:25PM +0200, Hans Petter Selasky wrote: > 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. > Changing the ACK ratio seems to be okay in most cases, a paper I wrote about this was published this week: https://onlinelibrary.wiley.com/doi/10.1002/sat.1466 It focuses on QUIC, but congestion control dynamics don't change with the protocol. You should be able to read there, but if not I'm happy to send anyone a pdf. - Tom