From mboxrd@z Thu Jan 1 00:00:00 1970 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 A749EC433EF for ; Fri, 14 Jan 2022 22:21:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230389AbiANWVC (ORCPT ); Fri, 14 Jan 2022 17:21:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230380AbiANWVC (ORCPT ); Fri, 14 Jan 2022 17:21:02 -0500 Received: from mail-yb1-xb31.google.com (mail-yb1-xb31.google.com [IPv6:2607:f8b0:4864:20::b31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D4C4C06161C for ; Fri, 14 Jan 2022 14:21:02 -0800 (PST) Received: by mail-yb1-xb31.google.com with SMTP id z22so27182964ybi.11 for ; Fri, 14 Jan 2022 14:21:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=DdW6l+hnl2A/9fPmp1Ui5Qe2IL3WZGRFxk5bdl0Lrnk=; b=F3S9kP2hnyNAyE16q+blRrSdFaHK9bN2MZwahIQBR08BxTsR+yltlO356a+iuV4rOW JNvwEqBjWxWG9mD0WnGKDtY1aiqbnLv7XoK4HYEORL4zdJMHZ1s01m3K1YzR6g2P5OVo CM1iqTdIaec72CQHMuHG50FrCw4E3c0a5dMh8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=DdW6l+hnl2A/9fPmp1Ui5Qe2IL3WZGRFxk5bdl0Lrnk=; b=pfJsGhwmlWTpIyzD44sD2hcvS3PQNXOpu2Lhy2T+5fTI5eGxme5gnDL22AJN0Gfnsq 7J/DIgyruZb5CoEVUstNevIfynbF95IOtKSKs3Hf37SQPAAKx/6Lb3YfKduSSMcGXPW6 VDBzEzXqAzOTIJOI5grF/dieZApvhnmQPO+tURiNIRZGimluGXAM3odN5UtVIuPua7// iMccS0sml9yfrs9w5m304NcSPK4z1QieMsykt3TLI2YJ5A2Ee5TaDOOhDLNq8+IW/mGP zE/o6OLj3RgSzjyn9MNtl7XovAysIiBC3JcDC9QIEnB7q9dLsNwvExtXZ8uy0GobM7/s pZ+g== X-Gm-Message-State: AOAM5305tm6G1dbR2iX/RW8KKHOUDArGlO1yGVsVHajrvDWmNdy13b5r lGlcwCnhXPhiU4qXunQMFlhWlPGRUffH97ZAiZXIg2Ox6I1xtHAN X-Google-Smtp-Source: ABdhPJwZHNor0OBeUymdSE9MD8tbiW9PjUgEdrJ/+d/zqxhgb5HqLrsPpW5KqTgZCVVX2ZLVV5OjKiyMv5A6w3EMI/c= X-Received: by 2002:a25:51c2:: with SMTP id f185mr9453004ybb.677.1642198861338; Fri, 14 Jan 2022 14:21:01 -0800 (PST) MIME-Version: 1.0 References: <20220111192952.49040-1-ivan@cloudflare.com> In-Reply-To: From: Ivan Babrou Date: Fri, 14 Jan 2022 14:20:50 -0800 Message-ID: Subject: Re: [PATCH bpf-next] tcp: bpf: Add TCP_BPF_RCV_SSTHRESH for bpf_setsockopt To: Dave Taht Cc: bpf , Linux Kernel Network Developers , LKML , kernel-team , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eric Dumazet Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Jan 13, 2022 at 9:44 PM Dave Taht wrote: > Yes, but with the caveats below. I'm fine with you just saying round trips, > and making this api possible. > > It would comfort me further if you could provide an actual scenario. The actual scenario is getting a response as quickly as possible on a fresh connection across long distances (200ms+ RTT). If an RPC response doesn't fit into the initial 64k of rcv_ssthresh, we end up requiring more roundrips to receive the response. Some customers are very picky about the latency they measure and cutting the extra roundtrips made a very visible difference in the tests. > See also: > > https://datatracker.ietf.org/doc/html/rfc6928 > > which predates packet pacing (are you using sch_fq?) We are using fq and bbr. > > Congestion window is a learned property, not a static number. You > > won't get a large initcwnd towards a poor connection. > > initcwnd is set globally or on a per route basis. With TCP_BPF_IW the world is your oyster.