Hi Xuan, > -----Original Message----- > From: Ding, Xuan <xuan.d...@intel.com> > Sent: Friday, June 17, 2022 5:34 PM > To: maxime.coque...@redhat.com; Xia, Chenbo <chenbo....@intel.com> > Cc: dev@dpdk.org; Hu, Jiayu <jiayu...@intel.com>; Ding, Xuan > <xuan.d...@intel.com> > Subject: [PATCH] doc: update async enqueue API usage > > From: Xuan Ding <xuan.d...@intel.com> > > This patch updates the correct usage for async enqueue APIs. > The rte_vhost_poll_enqueue_completed() needs to be called in time to avoid > packet loss due to full dma ring. > > Signed-off-by: Xuan Ding <xuan.d...@intel.com> > --- > doc/guides/prog_guide/vhost_lib.rst | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/doc/guides/prog_guide/vhost_lib.rst > b/doc/guides/prog_guide/vhost_lib.rst > index cd3f6caa9a..9cdd7da154 100644 > --- a/doc/guides/prog_guide/vhost_lib.rst > +++ b/doc/guides/prog_guide/vhost_lib.rst > @@ -488,3 +488,12 @@ For PA mode, page by page mapping may exceed > IOMMU's max capability, better to use 1G guest hugepage. > > For UIO driver, any VFIO related error message can be ignored. > + > +Async enqueue API usage > +-----------------------
I think it's better to make it as a sub-section of "Vhost asynchronous data path". > + > +In async enqueue path, rte_vhost_poll_enqueue_completed() needs to be > +called in time. Otherwise, calling rte_vhost_submit_enqueue_burst() all > +the time will cause the DMA ring to be full, which will result in > +packet loss eventually. There are two main reasons of calling rte_vhost_poll_enqueue_completed() timely, IMO: 1. notify the guest of DMA copy completed packets; 2. in case of DMA ring size is smaller than vring size, it can avoid packet drop caused by DMA ring full. Thanks, Jiayu > + > -- > 2.17.1
