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 AFB40C4332F for ; Fri, 4 Nov 2022 18:00:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231904AbiKDSAB (ORCPT ); Fri, 4 Nov 2022 14:00:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33392 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231204AbiKDR77 (ORCPT ); Fri, 4 Nov 2022 13:59:59 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D0A0A45A16 for ; Fri, 4 Nov 2022 10:59:58 -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 79CF4B82EFF for ; Fri, 4 Nov 2022 17:59:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EABADC433C1; Fri, 4 Nov 2022 17:59:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1667584796; bh=q5TKB1CM8Jc0B8Zxl83Fxzre7gqt/p60B+6q28/l8hY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=nWBuwabCdZtGb53K5xdYbO3q3YO6VJ7ScX0bKvGEgGwWUsmvDuwGcj7GzB3XW+dUx 7451tXNaXBdCpLr+XFuxLvyicwENhyW+EX9cMy4/dxn4ngm6Gg/zMY2l7FlR2lQU9q Dgb9PJjj4VPHGTty/In3t+nSKuLJpzHFoGame44qgIVNH5wv3XinudRElSE7VZygC8 lKBa/k+e2i/LLqk0UaZVfpG8MZASjY+JOHpMu92DJ5C3txydJjExLc9dj7qTn/LgsZ AHo0kUQUo4ANVOw9jh5KnnK1sgU4HBD2u6qBW0lqHrSySnWJ+p3iLBQcNUdTyxWau4 CXCL+6BFUkdqQ== Date: Fri, 4 Nov 2022 10:59:55 -0700 From: Jakub Kicinski To: Nick Child Cc: netdev@vger.kernel.org, nick.child@ibm.com, bjking1@linux.ibm.com, ricklind@us.ibm.com, dave.taht@gmail.com Subject: Re: [PATCH v2 net] ibmveth: Reduce maximum tx queues to 8 Message-ID: <20221104105955.2c3c74a7@kernel.org> In-Reply-To: <4f84f10b-9a79-17f6-7e2e-f65f0d2934cb@linux.ibm.com> References: <20221102183837.157966-1-nnac123@linux.ibm.com> <20221103205945.40aacd90@kernel.org> <4f84f10b-9a79-17f6-7e2e-f65f0d2934cb@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 Fri, 4 Nov 2022 09:06:02 -0500 Nick Child wrote: > On 11/3/22 22:59, Jakub Kicinski wrote: > > On Wed, 2 Nov 2022 13:38:37 -0500 Nick Child wrote: > >> Previously, the maximum number of transmit queues allowed was 16. Due to > >> resource concerns, limit to 8 queues instead. > >> > >> Since the driver is virtualized away from the physical NIC, the purpose > >> of multiple queues is purely to allow for parallel calls to the > >> hypervisor. Therefore, there is no noticeable effect on performance by > >> reducing queue count to 8. > > > > I'm not sure if that's the point Dave was making but we should be > > influencing the default, not the MAX. Why limit the MAX? > > The MAX is always allocated in the drivers probe function. In the > drivers open and ethtool-set-channels functions we set > real_num_tx_queues. So the number of allocated queues is always MAX > but the number of queues actually in use may differ and can be set by > the user. > I hope this explains. Otherwise, please let me know. Perhaps I don't understand the worry. Is allowing 16 queues a problem because it limits how many instances the hypervisor can support? Or is the concern coming from your recent work on BQL and having many queues exacerbating buffer bloat?