Hi Jiayu, > -----Original Message----- > From: Hu, Jiayu <jiayu...@intel.com> > Sent: Monday, June 20, 2022 9:43 AM > To: Ding, Xuan <xuan.d...@intel.com>; maxime.coque...@redhat.com; Xia, > Chenbo <chenbo....@intel.com> > Cc: dev@dpdk.org > Subject: RE: [PATCH] doc: update async enqueue API usage > > 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".
That's a good idea, I will add this section as a sub-section accordingly. > > > + > > +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. Please see doc enriched in next version. Thanks, Xuan > > Thanks, > Jiayu > > > > + > > -- > > 2.17.1 >
