From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH net-next 04/11] tuntap: simplify error handling in tun_build_skb() Date: Mon, 10 Sep 2018 11:44:26 +0800 Message-ID: <372ec320-83cf-add5-acf7-27d876c3d604@redhat.com> References: <20180906040526.22518-1-jasowang@redhat.com> <20180906040526.22518-5-jasowang@redhat.com> <20180906130425-mutt-send-email-mst@kernel.org> <20180907101645-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org To: "Michael S. Tsirkin" Return-path: In-Reply-To: <20180907101645-mutt-send-email-mst@kernel.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 2018年09月07日 22:17, Michael S. Tsirkin wrote: > On Fri, Sep 07, 2018 at 11:22:00AM +0800, Jason Wang wrote: >>>> @@ -1668,6 +1668,9 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun, >>>> if (copied != len) >>>> return ERR_PTR(-EFAULT); >>>> + get_page(alloc_frag->page); >>>> + alloc_frag->offset += buflen; >>>> + >>> This adds an atomic op on XDP_DROP which is a data path >>> operation for some workloads. >> Yes, I have patch on top to amortize this, the idea is to have a very big >> refcount once after the frag was allocated and maintain a bias and decrease >> them all when allocating new frags.' > Why bother with refcounting for a drop though? It should be simple. > Right, let me fix this. Thanks