From: Ferruh Yigit <ferruh.yigit@intel.com>
To: Remy Horton <remy.horton@intel.com>,
David Marchand <david.marchand@6wind.com>,
dev@dpdk.org
Cc: wenzhuo.lu@intel.com, jingjing.wu@intel.com,
bernard.iremonger@intel.com, stable@dpdk.org,
Harry Van Haaren <harry.van.haaren@intel.com>
Subject: Re: [dpdk-stable] [PATCH] app/testpmd: add sanity checks when retrieving xstats
Date: Thu, 14 Jun 2018 11:55:08 +0100 [thread overview]
Message-ID: <1c72a061-db06-8fac-b1fa-3d0695686de9@intel.com> (raw)
In-Reply-To: <94ff9382-dbcd-1afd-b149-349653e1222e@intel.com>
On 6/14/2018 7:39 AM, Remy Horton wrote:
>
> On 13/06/2018 16:39, Ferruh Yigit wrote:
>> On 6/7/2018 9:15 AM, David Marchand wrote:
>>> Testpmd should not expect the xstats names and values arrays to be
>>> aligned: neither the arrays sizes, nor the order in which the values are.
>>
>> As far as I can see this assumption is everywhere in API implementation:
>> xstats names and values are aligned with same order.
>> The basic stat part of the xstats, implemented in ethdev layer, seems relying on
>> same assumption. Also looks like "xstat size" and "xstat_names size" used
>> interchangeably.
>>
>> And I don't see any case that mentions xstats.id is xstats_name index.
>> cc'ed Harry, to get more information about initial intention.
>>
>> the id value in xstats struct looks like duplication, but other than that, is
>> there any downside of using array index to mach name, value pair?
>> And do we really need another layer of indirection (and complexity) to mach
>> simple name,value key pair in xstats?
>
> When I was working on xstats one of my intentions was to allow PMDs to
> only return a subset of values for all the keys they declare, with
> xstats[idx].id==idx just being a coincidence that was not to be relied
> on.
APIs exist for getting subset of values (.._by_id) but they both assume
requested ids are array index.
As you said this works fine because of xstats[idx].id==idx
struct rte_eth_xstat_name { char name[]; }
struct rte_eth_xstat { uint64_t id; uint64_t value; }
These two structs are for basic key-value match.
But one has the "id" field, but other doesn't. If we use "id" as match, this
will be the index of xstat_name[]. This is extra complexity, and xstats is
already unnecessarily complex.
I am for documenting that "xstat_name" and "xstat" are aligned, both in size and
order, and array indexes are ids, clearly in API doc and continue with existing
implementation. What do you think?
> Since then there appears to have been several instances of rework,
> so no idea if this coincidence becoming an assumption was intentional or
> an oversight.
>
> ..Remy
>
next prev parent reply other threads:[~2018-06-14 10:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-07 8:15 David Marchand
2018-06-12 7:09 ` David Marchand
2018-06-12 8:38 ` Remy Horton
2018-06-13 15:39 ` Ferruh Yigit
2018-06-14 6:39 ` Remy Horton
2018-06-14 10:55 ` Ferruh Yigit [this message]
2018-06-14 19:33 ` Remy Horton
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