From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by dpdk.space (Postfix) with ESMTP id 0CD9FA0471 for ; Mon, 17 Jun 2019 12:06:01 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 1D1311BEB5; Mon, 17 Jun 2019 12:06:01 +0200 (CEST) Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by dpdk.org (Postfix) with ESMTP id 2B06B1BE6E for ; Mon, 17 Jun 2019 12:05:58 +0200 (CEST) X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 Jun 2019 03:05:58 -0700 Received: from bricha3-mobl.ger.corp.intel.com ([10.237.221.51]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 Jun 2019 03:05:56 -0700 Date: Mon, 17 Jun 2019 11:05:52 +0100 From: Bruce Richardson To: David Marchand Cc: Ye Xiaolong , Qi Zhang , Karlsson Magnus , Topel Bjorn , yuan.peng@intel.com, dev Message-ID: <20190617100552.GC527@bricha3-MOBL.ger.corp.intel.com> References: <20190617142303.85240-1-xiaolong.ye@intel.com> <20190617152723.GC76301@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.4 (2019-03-13) Subject: Re: [dpdk-dev] [PATCH v1] net/af_xdp: support need wakeup feature X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Mon, Jun 17, 2019 at 10:51:52AM +0200, David Marchand wrote: > On Mon, Jun 17, 2019 at 10:45 AM Ye Xiaolong wrote: > > > On 06/17, David Marchand wrote: > > >On Mon, Jun 17, 2019 at 9:42 AM Xiaolong Ye > > wrote: > > > > > >> This patch adds a new devarg to support the need_wakeup flag for Tx and > > >> fill rings, when this flag is set by the driver, it means that the > > >> userspace application has to explicitly wake up the kernel Rx or kernel > > Tx > > >> processing by issuing a syscall. Poll() can wake up both and sendto() or > > >> its alternatives will wake up Tx processing only. > > >> > > >> This feature is to provide efficient support for case that application > > and > > >> driver are executing on the same core. > > >> > > >> Signed-off-by: Xiaolong Ye > > >> --- > > >> > > >> Original busy poll feature has morphed into need_wakeup flag in > > >> kernel side, the main purpose is the same, that is to support both > > >> application and driver executing on the same core efficiently. > > >> > > >> kernel side patchset can be found at netdev mailing list. > > >> > > >> > > https://lore.kernel.org/netdev/CAJ8uoz2szX=+JXXAMyuVmvSsMXZuDqp6a8rjDQpTioxbZwxFmQ@mail.gmail.com/T/#t > > >> > > >> It is targeted for v5.3 > > >> > > > > > >- Is this really optional? Adding too many options is just a nightmare > > >later... > > > > Hmm, I think we can remove this option and alway turn the need_wakeup flag > > on > > since it provides better performance for 1 core case and doesn't downgrage > > the > > 2 core case performance. > > > > > > > >- I suppose this will break compilation with kernels that have af_xdp but > > >are < 5.3. > > > > Yes, that is true. It will break the compilation with early kernel, I feel > > it's > > sort of common issue, we enable some features in dpdk that's based on > > kernel > > features, then kernel side features keep evolving, we need to keep the > > pace, > > but it will hurt the compatiblity with the old kernel. > > > > What's dpdk's convention for handling this kind of case? Add some notes in > > doc > > to reminder the prerequisite or use the KERNEL_VERSION macro in code? > > > > Rather than a kernel version, you can check that XDP_USE_NEED_WAKEUP is > defined (present in the uapi kernel header). > +1 for this. Also, since AF_XDP is still fairly new with ongoing development on the kernel side, I think it is reasonable to limit out PMD to only working with sufficiently updated kernels. Hopefully in 6 months or so, the feature set we need should be locked down and we can specify a fixed baseline requirement. /Bruce