From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Yuval Mintz" Subject: Re: [RFC net-next 05/14] Fix intel/ixgbevf Date: Mon, 25 Jun 2012 14:23:08 +0300 Message-ID: <4FE84A1C.90901@broadcom.com> References: <1340118848-30978-1-git-send-email-yuvalmin@broadcom.com> <1340118848-30978-6-git-send-email-yuvalmin@broadcom.com> <4FE09D3F.4060305@intel.com> <1340122013.2486.14.camel@lb-tlvb-eilong.il.broadcom.com> <20120619110704.000045b2@unknown> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit Cc: eilong@broadcom.com, "Alexander Duyck" , netdev@vger.kernel.org, davem@davemloft.net, "Jeff Kirsher" To: "Greg Rose" Return-path: Received: from mms2.broadcom.com ([216.31.210.18]:2530 "EHLO mms2.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755572Ab2FYLZG (ORCPT ); Mon, 25 Jun 2012 07:25:06 -0400 In-Reply-To: <20120619110704.000045b2@unknown> Sender: netdev-owner@vger.kernel.org List-ID: >>>> * It's easy to be greedy for MSI-X vectors, but it >>>> really @@ -2022,8 +2022,9 @@ static int >>>> ixgbevf_set_interrupt_capability(struct ixgbevf_adapter *adapter) >>>> * than CPU's. So let's be conservative and only ask for >>>> * (roughly) twice the number of vectors as there are >>>> CPU's. */ >>>> + ncpu = min_t(int, num_online_cpus(), >>>> DEFAULT_MAX_NUM_RSS_QUEUES); v_budget = >>>> min(adapter->num_rx_queues + adapter->num_tx_queues, >>>> - (int)(num_online_cpus() * 2)) + >>>> NON_Q_VECTORS; >>>> + ncpu * 2) + NON_Q_VECTORS; >>>> >>>> /* A failure in MSI-X entry allocation isn't fatal, but >>>> it does >>>> * mean we disable MSI-X capabilities of the adapter. */ >>> This change is pointless on the ixgbevf driver. The VF hardware can >>> support at most 4 RSS queues. As such num_rx_queues + num_tx_queues >>> will never exceed 8 so you are essentially adding a necessary >>> min(x,8). >> >> It is pointless with the current value, but if someone will edit the >> kernel source code and replace the 8 with a 2, it will become >> meaningful. The compiler will optimize this part, and I think that for >> completion, it is best to keep this reference so a future default >> number change will not be missed. >> >> Eilon > > I don't feel there is any real point to making this change to the > ixgbevf driver. 82599 virtual functions have 3 MSI-X vectors, one of > which is for the mailbox and the other two can be shared with tx/rx > queue pairs or assigned separately to tx or rx queues. So this code is > pointless no matter what value is set for DEFAULT_MAX_NUM_RSS_QUEUES. > Perhaps the patches to the other drivers in your RFC will have some > effect but this one looks like a no-op for the ixgbevf driver so there > is no reason for it. > > - Greg > Hi Greg, Since we're changing the RFC to use a new wrapper function which should replace num_online_cpus (for these purpose), the next RFC version will still change this driver (for uniformity, if nothing else). Of course, if you would still have reservations for this change - send them. Thanks, Yuval