From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [net-next PATCH 2/5] ixgbe: increase default TX ring buffer to 1024 Date: Wed, 14 May 2014 15:54:37 -0400 (EDT) Message-ID: <20140514.155437.750583011696684472.davem@davemloft.net> References: <537399C2.8070908@intel.com> <20140514.134950.1208688313542719676.davem@davemloft.net> <20140514210935.5fc80c79@redhat.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: alexander.h.duyck@intel.com, netdev@vger.kernel.org, jeffrey.t.kirsher@intel.com, dborkman@redhat.com, fw@strlen.de, shemminger@vyatta.com, paulmck@linux.vnet.ibm.com, robert@herjulf.se, greearb@candelatech.com, john.r.fastabend@intel.com, danieltt@kth.se, zhouzhouyi@gmail.com To: brouer@redhat.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:53894 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751173AbaENTyk (ORCPT ); Wed, 14 May 2014 15:54:40 -0400 In-Reply-To: <20140514210935.5fc80c79@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Jesper Dangaard Brouer Date: Wed, 14 May 2014 21:09:35 +0200 > On Wed, 14 May 2014 13:49:50 -0400 (EDT) > David Miller wrote: > >> From: Alexander Duyck >> Date: Wed, 14 May 2014 09:28:50 -0700 >> >> > I'd say that it might be better to just add a note to the documentation >> > folder indicating what configuration is optimal for pktgen rather then >> > changing everyone's defaults to support one specific test. >> >> We could have drivers provide a pktgen config adjustment mechanism, >> so if someone starts pktgen then the device auto-adjusts to a pktgen >> optimal configuration (whatever that may entail). > > That might be problematic because changing the TX queue size cause the > ixgbe driver to reset the link. A minor issue for someone firing up a specialized network test tool like pktgen. > Notice that pktgen is ignoring BQL. I'm sort of hoping that BQL will > push back for real use-cases, to avoid the bad effects of increasing > the TX size. I think we need to think carefully about drivers configuring such huge per-queue TX queue sizes. If anything, we should be decreasing their size in the default configuration.