From: "Wiles, Keith" <keith.wiles@intel.com>
To: "Richardson, Bruce" <bruce.richardson@intel.com>
Cc: Olivier MATZ <olivier.matz@6wind.com>, "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] rte_ring features in use (or not)
Date: Wed, 25 Jan 2017 15:59:55 +0000 [thread overview]
Message-ID: <647B0F09-667B-41D2-A8E1-964F71D4C365@intel.com> (raw)
In-Reply-To: <20170125144809.GA26936@bricha3-MOBL3.ger.corp.intel.com>
Sent from my iPhone
> On Jan 25, 2017, at 7:48 AM, Bruce Richardson <bruce.richardson@intel.com> wrote:
>
>> On Wed, Jan 25, 2017 at 01:54:04PM +0000, Bruce Richardson wrote:
>>> On Wed, Jan 25, 2017 at 02:20:52PM +0100, Olivier MATZ wrote:
>>> On Wed, 25 Jan 2017 12:14:56 +0000, Bruce Richardson
>>> <bruce.richardson@intel.com> wrote:
>>>> Hi all,
>>>>
>>>> while looking at the rte_ring code, I'm wondering if we can simplify
>>>> that a bit by removing some of the code it in that may not be used.
>>>> Specifically:
>>>>
>>>> * Does anyone use the NIC stats functionality for debugging? I've
>>>> certainly never seen it used, and it's presence makes the rest less
>>>> readable. Can it be dropped?
>>>
>>> What do you call NIC stats? The stats that are enabled with
>>> RTE_LIBRTE_RING_DEBUG?
>>
>> Yes. By NIC I meant ring. :-(
>>>
> <snip>
>>> For the ring, in my opinion, the stats could be fully removed.
>>
>> That is my thinking too. For mempool, I'd wait to see the potential
>> performance hits before deciding whether or not to enable by default.
>> Having them run-time enabled may also be an option too - if the branches
>> get predicted properly, there should be little to no impact as we avoid
>> all the writes to the stats, which is likely to be where the biggest hit
>> is.
>>
>>>
>>>
>>>> * RTE_RING_PAUSE_REP_COUNT is set to be disabled at build time, and
>>>> so does anyone actually use this? Can it be dropped?
>>>
>>> This option looks like a hack to use the ring in conditions where it
>>> should no be used (preemptable threads). And having a compile-time
>>> option for this kind of stuff is not in vogue ;)
>>
> <snip>
>>>
>>>
>>>> * Who uses the watermarks feature as is? I know we have a sample app
>>>> that uses it, but there are better ways I think to achieve the same
>>>> goal while simplifying the ring implementation. Rather than have a
>>>> set watermark on enqueue, have both enqueue and dequeue functions
>>>> return the number of free or used slots available in the ring (in
>>>> case of enqueue, how many free there are, in case of dequeue, how
>>>> many items are available). Easier to implement and far more useful to
>>>> the app.
>>>
>>> +1
>>>
> Bonus question:
> * Do we know how widely used the enq_bulk/deq_bulk functions are? They
> are useful for unit tests, so they do have uses, but I think it would
> be good if we harmonized the return values between bulk and burst
> functions. Right now:
> enq_bulk - only enqueues all elements or none. Returns 0 for all, or
> negative error for none.
> enq_burst - enqueues as many elements as possible. Returns the number
> enqueued.
I do use the apis in pktgen and the difference in return values has got me once. Making them common would be great, but the problem is backward compat to old versions I would need to have an ifdef in pktgen now. So it seems like we moved the problem to the application.
I would like to see the old API kept and a new API with the new behavior. I know it adds another API but one of the API would be nothing more than wrapper function if not a macro.
Would that be more reasonable then changing the ABI?
> I think it would be better if bulk and burst both returned the number
> enqueued, and only differed in the case of the behaviour when not all
> elements could be enqueued.
>
> That would mean an API change for enq_bulk, where it would return only
> 0 or N, rather than 0 or negative. While we can map one set of return
> values to another inside the rte_ring library, I'm not sure I see a
> good reason to keep the old behaviour except for backward compatibility.
> Changing it makes it easier to switch between the two functions in
> code, and avoids confusion as to what the return values could be. Is
> it worth doing so? [My opinion is yes!]
>
>
> Regards,
> /Bruce
next prev parent reply other threads:[~2017-01-25 15:59 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-25 12:14 Bruce Richardson
2017-01-25 12:16 ` Bruce Richardson
2017-01-25 13:20 ` Olivier MATZ
2017-01-25 13:54 ` Bruce Richardson
2017-01-25 14:48 ` Bruce Richardson
2017-01-25 15:59 ` Wiles, Keith [this message]
2017-01-25 16:57 ` Bruce Richardson
2017-01-25 17:29 ` Ananyev, Konstantin
2017-01-31 10:53 ` Olivier Matz
2017-01-31 11:41 ` Bruce Richardson
2017-01-31 12:10 ` Bruce Richardson
2017-01-31 13:27 ` Olivier Matz
2017-01-31 13:46 ` Bruce Richardson
2017-01-25 22:27 ` Wiles, Keith
2017-01-25 16:39 ` Stephen Hemminger
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 00/19] ring cleanup and generalization Bruce Richardson
2017-02-14 8:32 ` Olivier Matz
2017-02-14 9:39 ` Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 01/19] app/pdump: fix duplicate macro definition Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 02/19] ring: remove split cacheline build setting Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 03/19] ring: create common structure for prod and cons metadata Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 04/19] ring: add a function to return the ring size Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 05/19] crypto/null: use ring size function Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 06/19] ring: eliminate duplication of size and mask fields Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 07/19] ring: remove debug setting Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 08/19] ring: remove the yield when waiting for tail update Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 09/19] ring: remove watermark support Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 10/19] ring: make bulk and burst fn return vals consistent Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 11/19] ring: allow enq fns to return free space value Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 12/19] examples/quota_watermark: use ring space for watermarks Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 13/19] ring: allow dequeue fns to return remaining entry count Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 14/19] ring: reduce scope of local variables Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 15/19] ring: separate out head index manipulation for enq/deq Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 16/19] ring: create common function for updating tail idx Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 17/19] ring: allow macros to work with any type of object Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 18/19] ring: add object size parameter to memory size calculation Bruce Richardson
2017-02-07 14:12 ` [dpdk-dev] [PATCH RFCv3 19/19] ring: add event ring implementation Bruce Richardson
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