From: Olivier Matz <olivier.matz@6wind.com>
To: "Wiles, Keith" <keith.wiles@intel.com>,
"Damjan Marion (damarion)" <damarion@cisco.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] Adding API to force freeing consumed buffers in TX ring
Date: Mon, 21 Nov 2016 16:06:32 +0100 [thread overview]
Message-ID: <aae1d111-4be0-4d5a-d436-6795cf18155e@6wind.com> (raw)
In-Reply-To: <27853C4C-2482-49E0-8F60-178473276CF5@intel.com>
Hi,
On 11/21/2016 03:33 PM, Wiles, Keith wrote:
>
>> On Nov 21, 2016, at 4:48 AM, Damjan Marion (damarion) <damarion@cisco.com> wrote:
>>
>>
>> Hi,
>>
>> Currently in VPP we do memcpy of whole packet when we need to do
>> replication as we cannot know if specific buffer is transmitted
>> from tx ring before we update it again (i.e. l2 header rewrite).
>>
>> Unless there is already a way to address this issue in DPDK which I’m not aware
>> of my proposal is that we provide mechanism for polling TX ring
>> for consumed buffers. This can be either completely new API or
>> extension of rte_etx_tx_burst (i.e. special case when nb_pkts=0).
>>
>> This will allows us to start polling tx ring when we expect some
>> mbuf back, instead of waiting for next tx burst (which we don’t know
>> when it will happen) and hoping that we will reach free_threshold soon.
>
> +1
>
> In Pktgen I have the problem of not being able to reclaim all of the TX mbufs to update them for the next set of packets to send. I know this is not a common case, but I do see the case where the application needs its mbufs freed off the TX ring. Currently you need to have at least a TX ring size of mbufs on hand to make sure you can send to a TX ring. If you allocate too few you run into a deadlock case as the number of mbufs on a TX ring does not hit the flush mark. If you are sending to multiple TX rings on the same numa node from the a single TX pool you have to understand the total number of mbufs you need to have allocated to hit the TX flush on each ring. Not a clean way to handle the problems as you may have limited memory or require some logic to add more mbufs for dynamic ports.
>
> Anyway it would be great to require a way to clean up the TX done ring, using nb_pkts == 0 is the simplest way, but a new API is fine too.
>>
>> Any thoughts?
Yes, it looks useful to have a such API.
I would prefer another function instead of diverting the meaning of
nb_pkts. Maybe this?
void rte_eth_tx_free_bufs(uint8_t port_id, uint16_t queue_id);
Regards,
Olivier
next prev parent reply other threads:[~2016-11-21 15:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-21 10:48 Damjan Marion (damarion)
2016-11-21 14:33 ` Wiles, Keith
2016-11-21 15:06 ` Olivier Matz [this message]
2016-11-21 15:25 ` Bruce Richardson
2016-11-22 20:41 ` Wiles, Keith
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