From: santosh <santosh.shukla@caviumnetworks.com>
To: Olivier Matz <olivier.matz@6wind.com>,
Andrew Rybchenko <arybchenko@solarflare.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 16:03:32 +0530 [thread overview]
Message-ID: <44211f68-9a31-8025-afd4-43f482bd4e87@caviumnetworks.com> (raw)
In-Reply-To: <20180201101423.k5yqxd5a2dk55qqw@platinum>
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>
next prev parent reply other threads:[~2018-02-01 10:33 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 [this message]
2018-02-01 14:02 ` Andrew Rybchenko
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=44211f68-9a31-8025-afd4-43f482bd4e87@caviumnetworks.com \
--to=santosh.shukla@caviumnetworks.com \
--cc=arybchenko@solarflare.com \
--cc=dev@dpdk.org \
--cc=jerin.jacob@caviumnetworks.com \
--cc=olivier.matz@6wind.com \
--cc=stable@dpdk.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).