From: Andrew Rybchenko <arybchenko@solarflare.com>
To: santosh <santosh.shukla@caviumnetworks.com>,
Olivier Matz <olivier.matz@6wind.com>
Cc: <dev@dpdk.org>, <stable@dpdk.org>, <jerin.jacob@caviumnetworks.com>
Subject: Re: [dpdk-stable] [dpdk-dev] [RFC v2 01/17] mempool: fix phys contig check if populate default skipped
Date: Thu, 1 Feb 2018 17:02:19 +0300 [thread overview]
Message-ID: <af5d2a70-36d1-e6ed-9ba4-75a73919fe65@solarflare.com> (raw)
In-Reply-To: <44211f68-9a31-8025-afd4-43f482bd4e87@caviumnetworks.com>
On 02/01/2018 01:33 PM, santosh wrote:
> On Thursday 01 February 2018 03:44 PM, Olivier Matz wrote:
>> On Thu, Feb 01, 2018 at 01:00:12PM +0300, Andrew Rybchenko wrote:
>>> On 02/01/2018 12:30 PM, santosh wrote:
>>>> On Thursday 01 February 2018 02:48 PM, Andrew Rybchenko wrote:
>>>>> On 02/01/2018 12:09 PM, santosh wrote:
>>>>>> On Thursday 01 February 2018 12:24 PM, Andrew Rybchenko wrote:
>>>>>>> On 02/01/2018 08:05 AM, santosh wrote:
>>>>>>>> On Wednesday 31 January 2018 10:15 PM, Olivier Matz wrote:
>>>>>>>>> On Tue, Jan 23, 2018 at 01:15:56PM +0000, Andrew Rybchenko wrote:
>>>>>>>>>> There is not specified dependency between rte_mempool_populate_default()
>>>>>>>>>> and rte_mempool_populate_iova(). So, the second should not rely on the
>>>>>>>>>> fact that the first adds capability flags to the mempool flags.
>>>>>>>>>>
>>>>>>>>>> Fixes: 65cf769f5e6a ("mempool: detect physical contiguous objects")
>>>>>>>>>> Cc: stable@dpdk.org
>>>>>>>>>>
>>>>>>>>>> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
>>>>>>>>> Looks good to me. I agree it's strange that the mp->flags are
>>>>>>>>> updated with capabilities only in rte_mempool_populate_default().
>>>>>>>>> I see that this behavior is removed later in the patchset since the
>>>>>>>>> get_capa() is removed!
>>>>>>>>>
>>>>>>>>> However maybe this single patch could go in 18.02.
>>>>>>>>> +Santosh +Jerin since it's mostly about Octeon.
>>>>>>>> rte_mempool_xmem_size should return correct size if MEMPOOL_F_CAPA_BLK_ALIGNED_OBJECTS flag
>>>>>>>> is set in 'mp->flags'. Thats why _ops_get_capabilities() called in _populate_default() but not
>>>>>>>> at _populate_iova().
>>>>>>>> I think, this 'alone' patch may break octeontx mempool.
>>>>>>> The patch does not touch rte_mempool_populate_default().
>>>>>>> _ops_get_capabilities() is still called there before
>>>>>>> rte_mempool_xmem_size(). The theoretical problem which
>>>>>>> the patch tries to fix is the case when
>>>>>>> rte_mempool_populate_default() is not called at all. I.e. application
>>>>>>> calls _ops_get_capabilities() to get flags, then, together with
>>>>>>> mp->flags, calls rte_mempool_xmem_size() directly, allocates
>>>>>>> calculated amount of memory and calls _populate_iova().
>>>>>>>
>>>>>> In that case, Application does like below:
>>>>>>
>>>>>> /* Get mempool capabilities */
>>>>>> mp_flags = 0;
>>>>>> ret = rte_mempool_ops_get_capabilities(mp, &mp_flags);
>>>>>> if ((ret < 0) && (ret != -ENOTSUP))
>>>>>> return ret;
>>>>>>
>>>>>> /* update mempool capabilities */
>>>>>> mp->flags |= mp_flags;
>>>>> Above line is not mandatory. "mp->flags | mp_flags" could be simply
>>>>> passed to rte_mempool_xmem_size() below.
>>>>>
>>>> That depends and again upto application requirement, if app further down
>>>> wants to refer mp->flags for _align/_contig then better update to mp->flags.
>>>>
>>>> But that wasn't the point of discussion, I'm trying to understand that
>>>> w/o this patch, whats could be the application level problem?
>>> The problem that it is fragile. If application does not use
>>> rte_mempool_populate_default() it has to care about addition
>>> of mempool capability flags into mempool flags. If it is not done,
>>> rte_mempool_populate_iova/virt/iova_tab() functions will work
>>> incorrectly since F_CAPA_PHYS_CONTIG and
>>> F_CAPA_BLK_ALIGNED_OBJECTS are missing.
>>>
>>> The idea of the patch is to make it a bit more robust. I have no
>>> idea how it can break something. If capability flags are already
>>> there - no problem. If no, just make sure that we locally have them.
>> The example given by Santosh will work, but it is *not* the role of the
>> application to update the mempool flags. And nothing says that it is mandatory
>> to call rte_mempool_ops_get_capabilities() before the populate functions.
>>
>> For instance, in testpmd it calls rte_mempool_populate_anon() when using
>> anonymous memory. The capabilities will never be updated in mp->flags.
> Valid case and I agree with your example and explanation.
> With nits change:
> mp->flags |= mp_capa_flags;
>
> Acked-by: Santosh Shukla <santosh.shukla@caviumnetworks.com>
I'll submit the patch separately with this minor change. Thanks.
next prev parent reply other threads:[~2018-02-01 14:03 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1511539591-20966-1-git-send-email-arybchenko@solarflare.com>
[not found] ` <1516713372-10572-1-git-send-email-arybchenko@solarflare.com>
2018-01-23 13:15 ` [dpdk-stable] " Andrew Rybchenko
2018-01-31 16:45 ` Olivier Matz
2018-02-01 5:05 ` santosh
2018-02-01 6:54 ` Andrew Rybchenko
2018-02-01 9:09 ` santosh
2018-02-01 9:18 ` [dpdk-stable] [dpdk-dev] " Andrew Rybchenko
2018-02-01 9:30 ` santosh
2018-02-01 10:00 ` Andrew Rybchenko
2018-02-01 10:14 ` Olivier Matz
2018-02-01 10:33 ` santosh
2018-02-01 14:02 ` Andrew Rybchenko [this message]
2018-02-01 10:17 ` santosh
2018-02-01 14:02 ` [dpdk-stable] [PATCH] " Andrew Rybchenko
2018-02-05 23:53 ` Thomas Monjalon
[not found] ` <1521994855-8808-1-git-send-email-arybchenko@solarflare.com>
2018-03-25 16:20 ` [dpdk-stable] [PATCH v2 01/11] mempool: fix memhdr leak when no objects are populated Andrew Rybchenko
[not found] ` <1522080591-24705-1-git-send-email-arybchenko@solarflare.com>
2018-03-26 16:09 ` [dpdk-stable] [PATCH v3 " Andrew Rybchenko
2018-04-06 15:50 ` Olivier Matz
[not found] ` <1523885080-17168-1-git-send-email-arybchenko@solarflare.com>
2018-04-16 13:24 ` [dpdk-stable] [PATCH v4 " Andrew Rybchenko
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