From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DDE012910B for ; Tue, 16 May 2023 19:23:13 +0000 (UTC) Received: from mail.toke.dk (mail.toke.dk [IPv6:2a0c:4d80:42:2001::664]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E4857682 for ; Tue, 16 May 2023 12:23:10 -0700 (PDT) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=toke.dk; s=20161023; t=1684264988; bh=1p1Bnkvkp8DLKar/WrJYGPKNedFi9A3XCKlu91C48ZE=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=sesW/jX8hHUuwQAahPgOyO0h3icjc3LXC+NVuLXWNe3JSgCd4R3ZJPsPK/lAXTOSw tvftalRe+UBvQu8FWLP8VaJPICGJ4E/C5V1O0mS9ALK4LSLk2cDQNEOTE/2KV3gngT 1zSXkUgFunhJoYxhIqIl8/LMuJub2XWX8GFTjM3OqcyyHWp8GPK6h5DVWl0dCI/aXu aDbKZJy8ozMmssxNHGnPzEu0jiKM3BOHzkIpEbCAt6Wzq4eHiLDccEaBTXySnorWMf PU13BGzehBUsxDM4xvGmuwWTPiyb1cDE03/3SPrEWK+C36HG/QVPC0/68WCCV9zhEi 0sEIxiWJQ/ULw== To: Thorsten Glaser , Stephen Hemminger Cc: Jakub Kicinski , netdev@vger.kernel.org, Haye.Haehne@telekom.de Subject: Re: knob to disable locally-originating qdisc optimisation? In-Reply-To: <998e27d4-8a-2fd-7495-a8448a5427f9@tarent.de> References: <8a8c3e3b-b866-d723-552-c27bb33788f3@tarent.de> <20230427132126.48b0ed6a@kernel.org> <20230427163715.285e709f@hermes.local> <998e27d4-8a-2fd-7495-a8448a5427f9@tarent.de> Date: Tue, 16 May 2023 21:23:08 +0200 X-Clacks-Overhead: GNU Terry Pratchett Message-ID: <877ct8cc83.fsf@toke.dk> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Thorsten Glaser writes: > On Thu, 27 Apr 2023, Stephen Hemminger wrote: > >>On Thu, 27 Apr 2023 13:21:26 -0700 >>Jakub Kicinski wrote: > >>> Doesn't ring a bell, what's your setup? > > Intel NUC with Debian bullseye on it and a custom qdisc that > limits and delays outgoing traffic, therefore occasionally > returning NULL from .dequeue even if the qdisc is not empty. > > iperf3 sending from the same NUC to a device on the network > behind that qdisc where the corresponding iperf server runs. > >>It might be BQL trying to limit outstanding packets locally. > > Possibly? Sounds like it's TSQ kicking in? The objective of that is to provide the maximum backpressure against the application socket buffer, precisely so the application can better react to congestion. Turning that off isn't going to help your E2E latency, quite the contrary. Pushing stuff into a qdisc so it can be ECN-marked is also nonsensical for locally generated traffic; you don't need the ECN roundtrip, you can just directly tell the local TCP sender to slow down (which is exactly what TSQ does). -Toke