From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [net-next PATCH 2/7] mlx4: use napi_consume_skb API to get bulk free operations Date: Wed, 09 Mar 2016 16:03:20 -0500 (EST) Message-ID: <20160309.160320.1535201013338177802.davem@davemloft.net> References: <20160308.142422.1791364638495761357.davem@davemloft.net> <20160309120039.38cfdb88@redhat.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: brouer@redhat.com, netdev@vger.kernel.org, eugenia@mellanox.com, alexei.starovoitov@gmail.com, saeedm@mellanox.com, gerlitz.or@gmail.com To: alexander.duyck@gmail.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:33836 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753912AbcCIVDW (ORCPT ); Wed, 9 Mar 2016 16:03:22 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: From: Alexander Duyck Date: Wed, 9 Mar 2016 08:47:58 -0800 > On Wed, Mar 9, 2016 at 3:00 AM, Jesper Dangaard Brouer > wrote: >> Passing the budget down was Alex'es design. Axel any thoughts? > > I'd say just use dev_consume_skb_any in the bulk free instead of > dev_consume_skb_irq. This is slow path, as you said, so it shouldn't > come up often. Agreed. >> I do wonder how expensive this check is... as it goes into a code >> hotpath, which is very unlikely. The good thing would be, that we >> handle if buggy drivers call this function from a none softirq context >> (as these bugs could be hard to catch). >> >> Can netpoll ever be called from softirq or with BH disabled? (It >> disables IRQs, which would break calling kmem_cache_free_bulk). > > It is better for us to switch things out so that the napi_consume_skb > is the fast path with dev_consume_skb_any as the slow. There are too > many scenarios where we could be invoking something that makes use of > this within the Tx path so it is probably easiest to just solve it > that way so we don't have to deal with it again in the future. Indeed.