From: Olivier Matz <olivier.matz@6wind.com>
To: "Lu, Wenzhuo" <wenzhuo.lu@intel.com>,
Stephen Hemminger <stephen@networkplumber.org>
Cc: "dev@dpdk.org" <dev@dpdk.org>, "Tao, Zhe" <zhe.tao@intel.com>
Subject: Re: [dpdk-dev] [PATCH 2/8] lib/librte_ether: defind RX/TX lock mode
Date: Thu, 9 Jun 2016 09:50:57 +0200 [thread overview]
Message-ID: <57591FE1.9070908@6wind.com> (raw)
In-Reply-To: <6A0DE07E22DDAD4C9103DF62FEBC090903483A7F@shsmsx102.ccr.corp.intel.com>
Hi,
On 06/08/2016 09:34 AM, Lu, Wenzhuo wrote:
> Hi Stephen,
>
>
>> -----Original Message-----
>> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
>> Sent: Wednesday, June 8, 2016 10:16 AM
>> To: Lu, Wenzhuo
>> Cc: dev@dpdk.org; Tao, Zhe
>> Subject: Re: [dpdk-dev] [PATCH 2/8] lib/librte_ether: defind RX/TX lock mode
>>
>> On Mon, 6 Jun 2016 13:40:47 +0800
>> Wenzhuo Lu <wenzhuo.lu@intel.com> wrote:
>>
>>> Define lock mode for RX/TX queue. Because when resetting the device we
>>> want the resetting thread to get the lock of the RX/TX queue to make
>>> sure the RX/TX is stopped.
>>>
>>> Using next ABI macro for this ABI change as it has too much impact. 7
>>> APIs and 1 global variable are impacted.
>>>
>>> Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
>>> Signed-off-by: Zhe Tao <zhe.tao@intel.com>
>>
>> Why does this patch set make a different assumption the rest of the DPDK?
>>
>> The rest of the DPDK operates on the principle that the application is smart
>> enough to stop the device before making changes. There is no equivalent to the
>> Linux kernel RTNL mutex. The API assumes application threads are well behaved
>> and will not try and sabotage each other.
>>
>> If you restrict the reset operation to only being available when RX/TX is stopped,
>> then no lock is needed.
>>
>> The fact that it requires lots more locking inside each device driver implies to me
>> this is not correct way to architect this.
+1
I'm not sure adding locks is the proper way to do.
This is the application responsibility to ensure that:
- control functions are not called concurrently on the same port
- rx/tx functions are not called when the device is stopped/reset/...
However, I do think the usage paradigms of the ethdev api should be
better documented in rte_ethdev.h (ex: which functions can be called
concurrently). This would be a first step.
If we really want a helper API to do that in DPDK, the _next_ step
could be to add them in the ethdev api to achieve this. Maybe
something like (the function names could be better):
- to be called on one control thread:
rte_eth_stop_rxtx(port)
rte_eth_start_rxtx(port)
rte_eth_get_rxtx_state(port)
-> return "running" if at least one core is inside the rx/tx code
-> return "stopped" if all cores are outside the rx/tx code
- to be called on dataplane cores:
/* same than rte_eth_rx_burst(), but checks if rx/tx is allowed
* first, else do nothing */
rte_eth_rx_burst_interruptible()
rte_eth_tx_burst_interruptible()
The code of control thread could be:
rte_eth_stop_rxtx(port);
/* wait that all dataplane cores finished their processing */
while (rte_eth_get_rxtx_state(port) != stopped)
;
rte_eth_some_control_operation(port);
rte_eth_start_rxtx(port);
I think this could be done without any lock, just with the proper
memory barriers and a per-core status.
But this API may impose a paradigm to the application, and I'm not
sure the DPDK should do that.
Regards,
Olivier
next prev parent reply other threads:[~2016-06-09 7:51 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-06 5:40 [dpdk-dev] [PATCH 0/8] support reset of VF link Wenzhuo Lu
2016-06-06 5:40 ` [dpdk-dev] [PATCH 1/8] lib/librte_ether: support device reset Wenzhuo Lu
2016-06-06 5:40 ` [dpdk-dev] [PATCH 2/8] lib/librte_ether: defind RX/TX lock mode Wenzhuo Lu
2016-06-08 2:15 ` Stephen Hemminger
2016-06-08 7:34 ` Lu, Wenzhuo
2016-06-09 7:50 ` Olivier Matz [this message]
2016-06-12 5:25 ` Lu, Wenzhuo
2016-06-10 18:12 ` Stephen Hemminger
2016-06-12 5:27 ` Lu, Wenzhuo
2016-06-06 5:40 ` [dpdk-dev] [PATCH 3/8] ixgbe: RX/TX with lock on VF Wenzhuo Lu
2016-06-06 5:40 ` [dpdk-dev] [PATCH 4/8] ixgbe: implement device reset " Wenzhuo Lu
2016-06-06 5:40 ` [dpdk-dev] [PATCH 5/8] igb: RX/TX with lock " Wenzhuo Lu
2016-06-06 5:40 ` [dpdk-dev] [PATCH 6/8] igb: implement device reset " Wenzhuo Lu
2016-06-06 5:40 ` [dpdk-dev] [PATCH 7/8] i40e:RX/TX with lock " Wenzhuo Lu
2016-06-06 5:40 ` [dpdk-dev] [PATCH 8/8] i40e: implement device reset " Wenzhuo Lu
2016-06-15 3:03 ` [dpdk-dev] [PATCH v5 0/4] support reset of VF link Wenzhuo Lu
2016-06-15 3:03 ` [dpdk-dev] [PATCH v5 1/4] lib/librte_ether: support device reset Wenzhuo Lu
2016-06-16 15:31 ` Bruce Richardson
2016-06-16 15:36 ` Thomas Monjalon
2016-06-15 3:03 ` [dpdk-dev] [PATCH v5 2/4] ixgbe: implement device reset on VF Wenzhuo Lu
2016-06-15 3:03 ` [dpdk-dev] [PATCH v5 3/4] igb: " Wenzhuo Lu
2016-06-15 3:03 ` [dpdk-dev] [PATCH v5 4/4] i40e: " Wenzhuo Lu
2016-06-20 6:24 ` [dpdk-dev] [PATCH v6 0/4] support reset of VF link Wenzhuo Lu
2016-06-20 6:24 ` [dpdk-dev] [PATCH v6 1/4] lib/librte_ether: support device reset Wenzhuo Lu
2016-06-20 9:14 ` Jerin Jacob
2016-06-20 16:17 ` Stephen Hemminger
2016-06-21 3:51 ` Jerin Jacob
2016-06-21 6:14 ` Lu, Wenzhuo
2016-06-21 7:37 ` Jerin Jacob
2016-06-21 8:24 ` Lu, Wenzhuo
2016-06-21 8:55 ` Jerin Jacob
2016-06-21 9:26 ` Ananyev, Konstantin
2016-06-21 10:57 ` Jerin Jacob
2016-06-21 13:10 ` Ananyev, Konstantin
2016-06-21 13:30 ` Jerin Jacob
2016-06-21 14:03 ` Ananyev, Konstantin
2016-06-21 14:29 ` Jerin Jacob
2016-06-22 1:35 ` Lu, Wenzhuo
2016-06-22 2:37 ` Jerin Jacob
2016-06-22 3:32 ` Lu, Wenzhuo
2016-06-22 4:14 ` Jerin Jacob
2016-06-22 5:05 ` Lu, Wenzhuo
2016-06-22 6:10 ` Jerin Jacob
2016-06-22 6:42 ` Lu, Wenzhuo
2016-06-22 7:59 ` Jerin Jacob
2016-06-22 8:17 ` Thomas Monjalon
2016-06-22 8:25 ` Lu, Wenzhuo
2016-06-22 9:18 ` Thomas Monjalon
2016-06-22 11:06 ` Jerin Jacob
2016-06-23 0:45 ` Lu, Wenzhuo
2016-06-23 0:39 ` Lu, Wenzhuo
2016-06-21 0:51 ` Lu, Wenzhuo
2016-06-20 6:24 ` [dpdk-dev] [PATCH v6 2/4] ixgbe: implement device reset on VF Wenzhuo Lu
2016-06-20 6:24 ` [dpdk-dev] [PATCH v6 3/4] igb: " Wenzhuo Lu
2016-06-20 6:24 ` [dpdk-dev] [PATCH v6 4/4] i40e: " Wenzhuo Lu
2016-07-04 15:48 ` [dpdk-dev] [PATCH v6 0/4] support reset of VF link Luca Boccassi
2016-07-05 0:52 ` Lu, Wenzhuo
2016-07-05 9:52 ` Luca Boccassi
2016-07-06 0:45 ` Lu, Wenzhuo
2016-07-06 16:26 ` Luca Boccassi
[not found] ` <1467822182.32466.34.camel@brocade.com>
2016-07-07 1:09 ` Lu, Wenzhuo
2016-07-07 10:20 ` Luca Boccassi
2016-07-07 13:12 ` Lu, Wenzhuo
2016-07-07 16:19 ` Luca Boccassi
2016-07-08 0:14 ` Lu, Wenzhuo
2016-07-08 17:15 ` Luca Boccassi
2016-07-11 1:32 ` Lu, Wenzhuo
2016-07-11 12:02 ` Luca Boccassi
2016-07-11 15:43 ` Luca Boccassi
2016-07-12 1:19 ` Lu, Wenzhuo
2016-08-26 12:58 ` Luca Boccassi
2016-08-29 1:04 ` Lu, Wenzhuo
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