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 84EF0C38A2D for ; Tue, 25 Oct 2022 18:41:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232805AbiJYSl4 (ORCPT ); Tue, 25 Oct 2022 14:41:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39122 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232518AbiJYSlz (ORCPT ); Tue, 25 Oct 2022 14:41:55 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9986C108DFB for ; Tue, 25 Oct 2022 11:41:54 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 10444B8171E for ; Tue, 25 Oct 2022 18:41:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 88900C433D6; Tue, 25 Oct 2022 18:41:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666723311; bh=7NKoevC5iyxfqncmaGc1Od/SqDSvHchSLeOZFM0zPQE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=BtL16ConxBa4RHJlAS6OQDfsuqizt74H7WZd9xrqSkFFGcAls1RkKyH6t82TphwYs EUQT/hGVteeafnb4BItJ6DRyNajTUSjJmbOKimlwwhADlO3FexZUSfwfmRXMsyO6KA fia0HQz3DKti+frtSxBZGQluHq/MVk0xgZUert5iHNs2hJ+oTRllfEPlblnfS6AP4l acIKPM75Ti6e64D/bSdtE/2jmXOVYjLW5gOHu+pdZROTC8Lkhq0mJOw3tvm/pv160w MPSIned6OOS29z3Qd9VGII0kEMVisrSiN0llyCqnXmwPcyQm5SyXMb33EIH/qiqgrC /NabhYIJSsbrA== Date: Tue, 25 Oct 2022 11:41:48 -0700 From: Jakub Kicinski To: Nick Child Cc: netdev@vger.kernel.org, nick.child@ibm.com, dave.taht@gmail.com Subject: Re: [RFC PATCH net-next 0/1] ibmveth: Implement BQL Message-ID: <20221025114148.1bcf194b@kernel.org> In-Reply-To: <20221024213828.320219-1-nnac123@linux.ibm.com> References: <20221024213828.320219-1-nnac123@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, 24 Oct 2022 16:38:27 -0500 Nick Child wrote: > Labeled as RFC because I am unsure if adding Byte Queue Limits (BQL) is > positively effecting the ibmveth driver. BQL is common among network > drivers so I would like to incorporate it into the virtual ethernet > driver, ibmveth. But I am having trouble measuring its effects. > > From my understanding (and please correct me if I am wrong), BQL will > use the number of packets sent to the NIC to approximate the minimum > number of packets to enqueue to a netdev_queue without starving the NIC. > As a result, bufferbloat in the networking queues are minimized which > may allow for smaller latencies. > > After performing various netperf tests under differing loads and > priorities, I do not see any performance effect when comparing the > driver with and without BQL. The ibmveth driver is a virtual driver > which has an abstracted view of the NIC so I am comfortable without > seeing any performance deltas. That being said, I would like to know if > BQL is actually being enforced in some way. In other words, I would > like to observe a change in the number of queued bytes during BQL > implementations. Does anyone know of a mechanism to measure the length > of a netdev_queue? > > I tried creating a BPF script[1] to track the bytes in a netdev_queue > but again am not seeing any difference with and without BQL. I do not > believe anything is wrong with BQL (it is more likely that my tracing > is bad) but I would like to have some evidence of BQL having a > positive effect on the device. Any recommendations or advice would be > greatly appreciated. What qdisc are you using and what "netperf tests" are you running?