diff mbox series

[1/3] ethdev: fix telemetry xstats return null with some PMDs

Message ID 20220416010747.40714-2-fengchengwen@huawei.com (mailing list archive)
State Superseded, archived
Delegated to: Andrew Rybchenko
Headers
Series bugfix for ethdev telemetry |

Checks

Context Check Description
ci/checkpatch success coding style OK

Commit Message

Chengwen Feng April 16, 2022, 1:07 a.m. UTC 
  Currently the telemetry xstats uses rte_eth_xstats_get() to retrieve
the number of elements. But the value to be returned when the parameter
'xstats' is NULL is not specified, some PMDs (eg. hns3/ipn3ke/mvpp2/
axgbe) return zero while others return the required number of elements.

This patch uses rte_eth_xstats_get_names() instead of
rte_eth_xstats_get() because it returns the required number of elements
when the parameter 'xstats_name' is NULL.

Fixes: c190daedb9b1 ("ethdev: add telemetry callbacks")
Cc: stable@dpdk.org

Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
---
 lib/ethdev/rte_ethdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Stephen Hemminger April 16, 2022, 1:38 a.m. UTC | #1 
On Sat, 16 Apr 2022 09:07:45 +0800
Chengwen Feng <fengchengwen@huawei.com> wrote:

> Currently the telemetry xstats uses rte_eth_xstats_get() to retrieve
> the number of elements. But the value to be returned when the parameter
> 'xstats' is NULL is not specified, some PMDs (eg. hns3/ipn3ke/mvpp2/
> axgbe) return zero while others return the required number of elements.

Lets fix the PMD's this impacts other code as well.
Andrew Rybchenko April 21, 2022, 6:49 a.m. UTC | #2 
On 4/16/22 04:38, Stephen Hemminger wrote:
> On Sat, 16 Apr 2022 09:07:45 +0800
> Chengwen Feng <fengchengwen@huawei.com> wrote:
> 
>> Currently the telemetry xstats uses rte_eth_xstats_get() to retrieve
>> the number of elements. But the value to be returned when the parameter
>> 'xstats' is NULL is not specified, some PMDs (eg. hns3/ipn3ke/mvpp2/
>> axgbe) return zero while others return the required number of elements.
> 
> Lets fix the PMD's this impacts other code as well.

+1
Chengwen Feng April 24, 2022, 3:44 a.m. UTC | #3 
The root cause is: when the xstats is NULL and n less than required number of
elements is zero, the return value of rte_eth_xstats_get is ambiguous from
rte_ethdev.h's declaration.

But the implementation of rte_eth_xstats_get return required number of elements
when xstats is NULL and n less than required number of elements.

There are two modification schemes:
a) the value of xstats cannot be NULL, and the value of n must be greater than
   or equal to the required number, otherwise, an error code is returned.
b) define the behavior as the same as rte_eth_xstats_get_names, which means return
   required number of elelement when xstats is NULL and n less than required number
   of elements.

I prefer the scheme a because rte_eth_xstats_get and rte_eth_xstats_get_name are
symbiotic, and it's not necessary to both implement the same logic.

Also for scheme a, there is no need to modify the PMD implementation.

What about your opinions ?

On 2022/4/21 14:49, Andrew Rybchenko wrote:
> On 4/16/22 04:38, Stephen Hemminger wrote:
>> On Sat, 16 Apr 2022 09:07:45 +0800
>> Chengwen Feng <fengchengwen@huawei.com> wrote:
>>
>>> Currently the telemetry xstats uses rte_eth_xstats_get() to retrieve
>>> the number of elements. But the value to be returned when the parameter
>>> 'xstats' is NULL is not specified, some PMDs (eg. hns3/ipn3ke/mvpp2/
>>> axgbe) return zero while others return the required number of elements.
>>
>> Lets fix the PMD's this impacts other code as well.
> 
> +1
> 
> .
Morten Brørup April 25, 2022, 10:16 a.m. UTC | #4 
> From: fengchengwen [mailto:fengchengwen@huawei.com]
> Sent: Sunday, 24 April 2022 05.45
> 
> The root cause is: when the xstats is NULL and n less than required
> number of
> elements is zero, the return value of rte_eth_xstats_get is ambiguous
> from
> rte_ethdev.h's declaration.
> 
> But the implementation of rte_eth_xstats_get return required number of
> elements
> when xstats is NULL and n less than required number of elements.
> 
> There are two modification schemes:
> a) the value of xstats cannot be NULL, and the value of n must be
> greater than
>    or equal to the required number, otherwise, an error code is
> returned.
> b) define the behavior as the same as rte_eth_xstats_get_names, which
> means return
>    required number of elelement when xstats is NULL and n less than
> required number
>    of elements.
> 
> I prefer the scheme a because rte_eth_xstats_get and
> rte_eth_xstats_get_name are
> symbiotic, and it's not necessary to both implement the same logic.
> 
> Also for scheme a, there is no need to modify the PMD implementation.
> 
> What about your opinions ?

This is an excellent proposal.

And if the documentation for rte_eth_xstats_get() refers to rte_eth_xstats_get_names() for getting the number of elements, it is perfect.

> 
> On 2022/4/21 14:49, Andrew Rybchenko wrote:
> > On 4/16/22 04:38, Stephen Hemminger wrote:
> >> On Sat, 16 Apr 2022 09:07:45 +0800
> >> Chengwen Feng <fengchengwen@huawei.com> wrote:
> >>
> >>> Currently the telemetry xstats uses rte_eth_xstats_get() to
> retrieve
> >>> the number of elements. But the value to be returned when the
> parameter
> >>> 'xstats' is NULL is not specified, some PMDs (eg.
> hns3/ipn3ke/mvpp2/
> >>> axgbe) return zero while others return the required number of
> elements.
> >>
> >> Lets fix the PMD's this impacts other code as well.
> >
> > +1
> >
> > .
>
Chengwen Feng April 28, 2022, 1:38 p.m. UTC | #5 
On 2022/4/25 18:16, Morten Brørup wrote:
>> From: fengchengwen [mailto:fengchengwen@huawei.com]
>> Sent: Sunday, 24 April 2022 05.45
>>
>> The root cause is: when the xstats is NULL and n less than required
>> number of
>> elements is zero, the return value of rte_eth_xstats_get is ambiguous
>> from
>> rte_ethdev.h's declaration.
>>
>> But the implementation of rte_eth_xstats_get return required number of
>> elements
>> when xstats is NULL and n less than required number of elements.
>>
>> There are two modification schemes:
>> a) the value of xstats cannot be NULL, and the value of n must be
>> greater than
>>    or equal to the required number, otherwise, an error code is
>> returned.
>> b) define the behavior as the same as rte_eth_xstats_get_names, which
>> means return
>>    required number of elelement when xstats is NULL and n less than
>> required number
>>    of elements.
>>
>> I prefer the scheme a because rte_eth_xstats_get and
>> rte_eth_xstats_get_name are
>> symbiotic, and it's not necessary to both implement the same logic.
>>
>> Also for scheme a, there is no need to modify the PMD implementation.
>>
>> What about your opinions ?
> 
> This is an excellent proposal.
> 
> And if the documentation for rte_eth_xstats_get() refers to rte_eth_xstats_get_names() for getting the number of elements, it is perfect.

Hi Morten,

   I did a deepin review and found that many application use rte_eth_xstats_get(port_id, NULL, 0),
and also many PMD already support return required number of entries when xstats is NULL. So in
the v2, I use the modified hns3/ipn3ke/mvpp2/axgbe PMD method and explicit return value when xstats
is NULL of rte_eth_xstats-get().

Thanks.

> 
>>
>> On 2022/4/21 14:49, Andrew Rybchenko wrote:
>>> On 4/16/22 04:38, Stephen Hemminger wrote:
>>>> On Sat, 16 Apr 2022 09:07:45 +0800
>>>> Chengwen Feng <fengchengwen@huawei.com> wrote:
>>>>
>>>>> Currently the telemetry xstats uses rte_eth_xstats_get() to
>> retrieve
>>>>> the number of elements. But the value to be returned when the
>> parameter
>>>>> 'xstats' is NULL is not specified, some PMDs (eg.
>> hns3/ipn3ke/mvpp2/
>>>>> axgbe) return zero while others return the required number of
>> elements.
>>>>
>>>> Lets fix the PMD's this impacts other code as well.
>>>
>>> +1
>>>
>>> .
>>
>
Morten Brørup April 28, 2022, 1:53 p.m. UTC | #6 
> From: fengchengwen [mailto:fengchengwen@huawei.com]
> Sent: Thursday, 28 April 2022 15.39
> 
> On 2022/4/25 18:16, Morten Brørup wrote:
> >> From: fengchengwen [mailto:fengchengwen@huawei.com]
> >> Sent: Sunday, 24 April 2022 05.45
> >>
> >> The root cause is: when the xstats is NULL and n less than required
> >> number of
> >> elements is zero, the return value of rte_eth_xstats_get is
> ambiguous
> >> from
> >> rte_ethdev.h's declaration.
> >>
> >> But the implementation of rte_eth_xstats_get return required number
> of
> >> elements
> >> when xstats is NULL and n less than required number of elements.
> >>
> >> There are two modification schemes:
> >> a) the value of xstats cannot be NULL, and the value of n must be
> >> greater than
> >>    or equal to the required number, otherwise, an error code is
> >> returned.
> >> b) define the behavior as the same as rte_eth_xstats_get_names,
> which
> >> means return
> >>    required number of elelement when xstats is NULL and n less than
> >> required number
> >>    of elements.
> >>
> >> I prefer the scheme a because rte_eth_xstats_get and
> >> rte_eth_xstats_get_name are
> >> symbiotic, and it's not necessary to both implement the same logic.
> >>
> >> Also for scheme a, there is no need to modify the PMD
> implementation.
> >>
> >> What about your opinions ?
> >
> > This is an excellent proposal.
> >
> > And if the documentation for rte_eth_xstats_get() refers to
> rte_eth_xstats_get_names() for getting the number of elements, it is
> perfect.
> 
> Hi Morten,
> 
>    I did a deepin review and found that many application use
> rte_eth_xstats_get(port_id, NULL, 0),
> and also many PMD already support return required number of entries
> when xstats is NULL. So in
> the v2, I use the modified hns3/ipn3ke/mvpp2/axgbe PMD method and
> explicit return value when xstats
> is NULL of rte_eth_xstats-get().

Instead of modifying the drivers, consider copying this code from rte_eth_xstats_get_names() to rte_eth_xstats_get():

	cnt_expected_entries = eth_dev_get_xstats_count(port_id);
	if (xstats_names == NULL || cnt_expected_entries < 0 ||
			(int)size < cnt_expected_entries)
		return cnt_expected_entries;

Just a suggestion. Either solution is fine with me.

> 
> Thanks.
> 
> >
> >>
> >> On 2022/4/21 14:49, Andrew Rybchenko wrote:
> >>> On 4/16/22 04:38, Stephen Hemminger wrote:
> >>>> On Sat, 16 Apr 2022 09:07:45 +0800
> >>>> Chengwen Feng <fengchengwen@huawei.com> wrote:
> >>>>
> >>>>> Currently the telemetry xstats uses rte_eth_xstats_get() to
> >> retrieve
> >>>>> the number of elements. But the value to be returned when the
> >> parameter
> >>>>> 'xstats' is NULL is not specified, some PMDs (eg.
> >> hns3/ipn3ke/mvpp2/
> >>>>> axgbe) return zero while others return the required number of
> >> elements.
> >>>>
> >>>> Lets fix the PMD's this impacts other code as well.
> >>>
> >>> +1
> >>>
> >>> .
> >>
> >
>
diff mbox series

Patch

diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
index 29a3d80466..615383bde2 100644
--- a/lib/ethdev/rte_ethdev.c
+++ b/lib/ethdev/rte_ethdev.c
@@ -5558,7 +5558,7 @@  eth_dev_handle_port_xstats(const char *cmd __rte_unused,
 	if (!rte_eth_dev_is_valid_port(port_id))
 		return -1;
 
-	num_xstats = rte_eth_xstats_get(port_id, NULL, 0);
+	num_xstats = rte_eth_xstats_get_names(port_id, NULL, 0);
 	if (num_xstats < 0)
 		return -1;