From: Stephen Hemminger <stephen@networkplumber.org>
To: Alejandro Lucero <alejandro.lucero@netronome.com>
Cc: dev <dev@dpdk.org>
Subject: Re: [dpdk-dev] rte_eth_rx_queue_count accuracy
Date: Mon, 21 Sep 2015 15:41:30 -0700 [thread overview]
Message-ID: <20150921154130.5b5dd845@urahara> (raw)
In-Reply-To: <CAD+H992XvC79Nwp5jHFZksC-egsDs413oShz=-Aq7AuOAsA2kw@mail.gmail.com>
On Fri, 18 Sep 2015 11:33:36 +0100
Alejandro Lucero <alejandro.lucero@netronome.com> wrote:
> I have seen the API definition says nothing about accuracy but some PMD
> implementations sacrifice accuracy for the sake of performance. If I'm not
> understanding the code wrongly i40e and ixgbe check DD bit just for the
> first descriptor in a group of 4, and they take all of them as used if the
> first descriptor is used.
>
> By other hand, they do a "heavy" calculation when the descriptor ring wraps
> which does not make sense (to me) if same performance goal is used.
>
> There are PMDs not supporting this option and I can not see any app or
> example using it so I do not know how important is this function, its
> accuracy and its performance impact. Can someone comment on this?
>
> Thanks
I have version of this for virtio/vmxnet3
It is useful when using the interrupt control mode.
next prev parent reply other threads:[~2015-09-21 22:41 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-18 10:33 Alejandro Lucero
2015-09-21 22:41 ` Stephen Hemminger [this message]
2015-09-22 10:40 ` Alejandro Lucero
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