From: "Hu, Jiayu" <jiayu.hu@intel.com>
To: "Ding, Xuan" <xuan.ding@intel.com>,
"maxime.coquelin@redhat.com" <maxime.coquelin@redhat.com>,
"Xia, Chenbo" <chenbo.xia@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: RE: [PATCH] doc: update async enqueue API usage
Date: Mon, 20 Jun 2022 02:10:29 +0000 [thread overview]
Message-ID: <31178840c26144ebabd3752c9afb7109@intel.com> (raw)
In-Reply-To: <64663b8d8c0c4a99b34438c3ccc3ba67@intel.com>
Hi Xuan,
> -----Original Message-----
> From: Hu, Jiayu
> Sent: Monday, June 20, 2022 9:43 AM
> To: Ding, Xuan <xuan.ding@intel.com>; maxime.coquelin@redhat.com; Xia,
> Chenbo <chenbo.xia@intel.com>
> Cc: dev@dpdk.org
> Subject: RE: [PATCH] doc: update async enqueue API usage
>
> Hi Xuan,
>
> > -----Original Message-----
> > From: Ding, Xuan <xuan.ding@intel.com>
> > Sent: Friday, June 17, 2022 5:34 PM
> > To: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>
> > Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Ding, Xuan
> > <xuan.ding@intel.com>
> > Subject: [PATCH] doc: update async enqueue API usage
> >
> > From: Xuan Ding <xuan.ding@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.ding@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.
I'd like to clarify #2 a little: not only for the case that DMA ring size < vring size.
Even if DMA ring size > vring size, it's possible dropping packets as a result of
DMA ring full.
Thanks,
Jiayu
>
> Thanks,
> Jiayu
>
>
> > +
> > --
> > 2.17.1
next prev parent reply other threads:[~2022-06-20 2:10 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-17 9:34 xuan.ding
2022-06-20 1:43 ` Hu, Jiayu
2022-06-20 2:08 ` Ding, Xuan
2022-06-20 2:10 ` Hu, Jiayu [this message]
2022-06-21 7:21 ` [PATCH v2] " xuan.ding
2022-06-21 13:22 ` Xia, Chenbo
2022-06-22 1:13 ` Ding, Xuan
2022-06-23 3:09 ` Xia, Chenbo
2022-07-01 13:54 ` Maxime Coquelin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=31178840c26144ebabd3752c9afb7109@intel.com \
--to=jiayu.hu@intel.com \
--cc=chenbo.xia@intel.com \
--cc=dev@dpdk.org \
--cc=maxime.coquelin@redhat.com \
--cc=xuan.ding@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).