From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sowmini Varadhan Subject: Re: [RFC PATCH 0/2] rx zero copy interface for af_packet Date: Tue, 31 Jan 2017 11:30:42 -0500 Message-ID: <20170131163042.GF8649@oracle.com> References: <20170127213132.14162.82951.stgit@john-Precision-Tower-5810> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: bjorn.topel@gmail.com, jasowang@redhat.com, ast@fb.com, alexander.duyck@gmail.com, brouer@redhat.com, john.r.fastabend@intel.com, netdev@vger.kernel.org To: John Fastabend Return-path: Received: from userp1040.oracle.com ([156.151.31.81]:22092 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751124AbdAaQcX (ORCPT ); Tue, 31 Jan 2017 11:32:23 -0500 Content-Disposition: inline In-Reply-To: <20170127213132.14162.82951.stgit@john-Precision-Tower-5810> Sender: netdev-owner@vger.kernel.org List-ID: On (01/27/17 13:33), John Fastabend wrote: > > This is an experimental implementation of rx zero copy for af_packet. > Its a bit rough and likely has errors but the plan is to clean it up > over the next few months. > > And seeing I said I would post it in another thread a few days back > here it is. One question/comment about this: sure, this saves us an skb copy on the rx side, but at least for the Tx side, I think there may be a trade-off between the overhead from the skb setup and the ease of offloading checksum (and UFO where it is available) to consider, even for PF_PACKET. Using PF_PACKET works well for stateless datagram protocols like UDP, and for UDP sockets, we find that just switching to Jumbo (to simulate a poor-man's-UFO) gives us significant improvement in both throughput and latency for our RDBMS workloads - and having the sk_buff facilitates using existing driver-kernel interfaces for offload easily, so while we may gain some perf improvment by shaving of the sk_buff overhead, the trade-off needs to be considered. --Sowmini