* [dpdk-stable] [PATCH] doc: add multi-proc shared lib mempool note
@ 2019-06-18 18:48 Gage Eads
2019-06-20 18:01 ` Andrew Rybchenko
2019-06-20 22:07 ` [dpdk-stable] [PATCH v2] " Gage Eads
0 siblings, 2 replies; 6+ messages in thread
From: Gage Eads @ 2019-06-18 18:48 UTC (permalink / raw)
To: dev; +Cc: olivier.matz, arybchenko, stable
The mempool library assigns handler ops indexes based on the dynamic load
order of mempool handlers. Indexes are used so a mempool can be used by
multiple processes, but this only works if all processes agree on the
mapping from index to mempool handler.
When using the '-d' argument, it's possible for different processes to load
mempool handlers in different orders, and thus have different
index->handler mappings. Using a mempool in multiple of such processes will
result in undefined behavior.
This commit adds a note to the mempool library programmer's guide warning
users against this.
Fixes: 449c49b93a6b ("mempool: support handler operations")
Cc: stable@dpdk.org
Signed-off-by: Gage Eads <gage.eads@intel.com>
---
doc/guides/prog_guide/mempool_lib.rst | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/doc/guides/prog_guide/mempool_lib.rst b/doc/guides/prog_guide/mempool_lib.rst
index 52a569f57..4470f6b38 100644
--- a/doc/guides/prog_guide/mempool_lib.rst
+++ b/doc/guides/prog_guide/mempool_lib.rst
@@ -133,6 +133,13 @@ For applications that use ``rte_pktmbuf_create()``, there is a config setting
(``RTE_MBUF_DEFAULT_MEMPOOL_OPS``) that allows the application to make use of
an alternative mempool handler.
+ .. note::
+
+ When running a DPDK application with shared libraries, mempool handler
+ shared objects specified with the '-d' EAL command-line parameter are
+ dynamically loaded. When running a multi-process application with shared
+ libraries, the -d arguments for mempool handlers *must be specified in the
+ same order for all processes* to ensure correct operation.
Use Cases
---------
--
2.13.6
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [dpdk-stable] [PATCH] doc: add multi-proc shared lib mempool note
2019-06-18 18:48 [dpdk-stable] [PATCH] doc: add multi-proc shared lib mempool note Gage Eads
@ 2019-06-20 18:01 ` Andrew Rybchenko
2019-06-20 19:07 ` Eads, Gage
2019-06-20 22:07 ` [dpdk-stable] [PATCH v2] " Gage Eads
1 sibling, 1 reply; 6+ messages in thread
From: Andrew Rybchenko @ 2019-06-20 18:01 UTC (permalink / raw)
To: Gage Eads, dev; +Cc: olivier.matz, stable
On 6/18/19 9:48 PM, Gage Eads wrote:
> The mempool library assigns handler ops indexes based on the dynamic load
> order of mempool handlers. Indexes are used so a mempool can be used by
> multiple processes, but this only works if all processes agree on the
> mapping from index to mempool handler.
>
> When using the '-d' argument, it's possible for different processes to load
> mempool handlers in different orders, and thus have different
> index->handler mappings. Using a mempool in multiple of such processes will
> result in undefined behavior.
>
> This commit adds a note to the mempool library programmer's guide warning
> users against this.
>
> Fixes: 449c49b93a6b ("mempool: support handler operations")
> Cc: stable@dpdk.org
>
> Signed-off-by: Gage Eads <gage.eads@intel.com>
> ---
> doc/guides/prog_guide/mempool_lib.rst | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/doc/guides/prog_guide/mempool_lib.rst b/doc/guides/prog_guide/mempool_lib.rst
> index 52a569f57..4470f6b38 100644
> --- a/doc/guides/prog_guide/mempool_lib.rst
> +++ b/doc/guides/prog_guide/mempool_lib.rst
> @@ -133,6 +133,13 @@ For applications that use ``rte_pktmbuf_create()``, there is a config setting
> (``RTE_MBUF_DEFAULT_MEMPOOL_OPS``) that allows the application to make use of
> an alternative mempool handler.
>
> + .. note::
> +
> + When running a DPDK application with shared libraries, mempool handler
> + shared objects specified with the '-d' EAL command-line parameter are
> + dynamically loaded. When running a multi-process application with shared
> + libraries, the -d arguments for mempool handlers *must be specified in the
> + same order for all processes* to ensure correct operation.
>
One more empty line is required here, other than that:
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
I think it is OK as a fix for stable branches.
In theory I think it is still technically possible to guarantee ops
indices correctness
using dedicated memzone (as Olivier suggested), but with sync up on
rte_mempool_{get,set}_ops() (which should be called when EAL is
initialized) and
reordering. However, it requires API breakage to avoid returning of
ops_index
on register (since it may change in secondary process on resync when EAL is
already initialized).
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [dpdk-stable] [PATCH] doc: add multi-proc shared lib mempool note
2019-06-20 18:01 ` Andrew Rybchenko
@ 2019-06-20 19:07 ` Eads, Gage
2019-06-21 7:25 ` Andrew Rybchenko
0 siblings, 1 reply; 6+ messages in thread
From: Eads, Gage @ 2019-06-20 19:07 UTC (permalink / raw)
To: Andrew Rybchenko, dev; +Cc: olivier.matz, stable
> -----Original Message-----
> From: Andrew Rybchenko [mailto:arybchenko@solarflare.com]
> Sent: Thursday, June 20, 2019 1:01 PM
> To: Eads, Gage <gage.eads@intel.com>; dev@dpdk.org
> Cc: olivier.matz@6wind.com; stable@dpdk.org
> Subject: Re: [PATCH] doc: add multi-proc shared lib mempool note
>
> On 6/18/19 9:48 PM, Gage Eads wrote:
> > The mempool library assigns handler ops indexes based on the dynamic
> > load order of mempool handlers. Indexes are used so a mempool can be
> > used by multiple processes, but this only works if all processes agree
> > on the mapping from index to mempool handler.
> >
> > When using the '-d' argument, it's possible for different processes to
> > load mempool handlers in different orders, and thus have different
> > index->handler mappings. Using a mempool in multiple of such processes
> > index->will
> > result in undefined behavior.
> >
> > This commit adds a note to the mempool library programmer's guide
> > warning users against this.
> >
> > Fixes: 449c49b93a6b ("mempool: support handler operations")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Gage Eads <gage.eads@intel.com>
> > ---
> > doc/guides/prog_guide/mempool_lib.rst | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/doc/guides/prog_guide/mempool_lib.rst
> > b/doc/guides/prog_guide/mempool_lib.rst
> > index 52a569f57..4470f6b38 100644
> > --- a/doc/guides/prog_guide/mempool_lib.rst
> > +++ b/doc/guides/prog_guide/mempool_lib.rst
> > @@ -133,6 +133,13 @@ For applications that use ``rte_pktmbuf_create()``,
> there is a config setting
> > (``RTE_MBUF_DEFAULT_MEMPOOL_OPS``) that allows the application to
> make use of
> > an alternative mempool handler.
> >
> > + .. note::
> > +
> > + When running a DPDK application with shared libraries, mempool
> handler
> > + shared objects specified with the '-d' EAL command-line parameter are
> > + dynamically loaded. When running a multi-process application with
> shared
> > + libraries, the -d arguments for mempool handlers *must be specified in
> the
> > + same order for all processes* to ensure correct operation.
> >
>
> One more empty line is required here, other than that:
> Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
Can do. Just for my understanding, why is the extra empty line required?
>
> I think it is OK as a fix for stable branches.
>
> In theory I think it is still technically possible to guarantee ops indices
> correctness using dedicated memzone (as Olivier suggested), but with sync
> up on
> rte_mempool_{get,set}_ops() (which should be called when EAL is
> initialized) and
> reordering. However, it requires API breakage to avoid returning of
> ops_index on register (since it may change in secondary process on resync
> when EAL is already initialized).
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [dpdk-stable] [PATCH] doc: add multi-proc shared lib mempool note
2019-06-20 19:07 ` Eads, Gage
@ 2019-06-21 7:25 ` Andrew Rybchenko
0 siblings, 0 replies; 6+ messages in thread
From: Andrew Rybchenko @ 2019-06-21 7:25 UTC (permalink / raw)
To: Eads, Gage, dev; +Cc: olivier.matz, stable
On 6/20/19 10:07 PM, Eads, Gage wrote:
>> -----Original Message-----
>> From: Andrew Rybchenko [mailto:arybchenko@solarflare.com]
>> Sent: Thursday, June 20, 2019 1:01 PM
>> To: Eads, Gage <gage.eads@intel.com>; dev@dpdk.org
>> Cc: olivier.matz@6wind.com; stable@dpdk.org
>> Subject: Re: [PATCH] doc: add multi-proc shared lib mempool note
>>
>> On 6/18/19 9:48 PM, Gage Eads wrote:
>>> The mempool library assigns handler ops indexes based on the dynamic
>>> load order of mempool handlers. Indexes are used so a mempool can be
>>> used by multiple processes, but this only works if all processes agree
>>> on the mapping from index to mempool handler.
>>>
>>> When using the '-d' argument, it's possible for different processes to
>>> load mempool handlers in different orders, and thus have different
>>> index->handler mappings. Using a mempool in multiple of such processes
>>> index->will
>>> result in undefined behavior.
>>>
>>> This commit adds a note to the mempool library programmer's guide
>>> warning users against this.
>>>
>>> Fixes: 449c49b93a6b ("mempool: support handler operations")
>>> Cc: stable@dpdk.org
>>>
>>> Signed-off-by: Gage Eads <gage.eads@intel.com>
>>> ---
>>> doc/guides/prog_guide/mempool_lib.rst | 7 +++++++
>>> 1 file changed, 7 insertions(+)
>>>
>>> diff --git a/doc/guides/prog_guide/mempool_lib.rst
>>> b/doc/guides/prog_guide/mempool_lib.rst
>>> index 52a569f57..4470f6b38 100644
>>> --- a/doc/guides/prog_guide/mempool_lib.rst
>>> +++ b/doc/guides/prog_guide/mempool_lib.rst
>>> @@ -133,6 +133,13 @@ For applications that use ``rte_pktmbuf_create()``,
>> there is a config setting
>>> (``RTE_MBUF_DEFAULT_MEMPOOL_OPS``) that allows the application to
>> make use of
>>> an alternative mempool handler.
>>>
>>> + .. note::
>>> +
>>> + When running a DPDK application with shared libraries, mempool
>> handler
>>> + shared objects specified with the '-d' EAL command-line parameter are
>>> + dynamically loaded. When running a multi-process application with
>> shared
>>> + libraries, the -d arguments for mempool handlers *must be specified in
>> the
>>> + same order for all processes* to ensure correct operation.
>>>
>> One more empty line is required here, other than that:
>> Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
> Can do. Just for my understanding, why is the extra empty line required?
https://doc.dpdk.org/guides/contributing/documentation.html#whitespace
* Add 2 blank lines before each section header.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [dpdk-stable] [PATCH v2] doc: add multi-proc shared lib mempool note
2019-06-18 18:48 [dpdk-stable] [PATCH] doc: add multi-proc shared lib mempool note Gage Eads
2019-06-20 18:01 ` Andrew Rybchenko
@ 2019-06-20 22:07 ` Gage Eads
2019-07-04 20:53 ` Thomas Monjalon
1 sibling, 1 reply; 6+ messages in thread
From: Gage Eads @ 2019-06-20 22:07 UTC (permalink / raw)
To: dev; +Cc: arybchenko, olivier.matz, stable
The mempool library assigns handler ops indexes based on the dynamic load
order of mempool handlers. Indexes are used so a mempool can be used by
multiple processes, but this only works if all processes agree on the
mapping from index to mempool handler.
When using the '-d' argument, it's possible for different processes to load
mempool handlers in different orders, and thus have different
index->handler mappings. Using a mempool in multiple of such processes will
result in undefined behavior.
This commit adds a note to the mempool library programmer's guide warning
users against this.
Fixes: 449c49b93a6b ("mempool: support handler operations")
Cc: stable@dpdk.org
Signed-off-by: Gage Eads <gage.eads@intel.com>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
---
doc/guides/prog_guide/mempool_lib.rst | 8 ++++++++
1 file changed, 8 insertions(+)
v2: add another empty line
diff --git a/doc/guides/prog_guide/mempool_lib.rst b/doc/guides/prog_guide/mempool_lib.rst
index 52a569f57..3bb84b0a6 100644
--- a/doc/guides/prog_guide/mempool_lib.rst
+++ b/doc/guides/prog_guide/mempool_lib.rst
@@ -133,6 +133,14 @@ For applications that use ``rte_pktmbuf_create()``, there is a config setting
(``RTE_MBUF_DEFAULT_MEMPOOL_OPS``) that allows the application to make use of
an alternative mempool handler.
+ .. note::
+
+ When running a DPDK application with shared libraries, mempool handler
+ shared objects specified with the '-d' EAL command-line parameter are
+ dynamically loaded. When running a multi-process application with shared
+ libraries, the -d arguments for mempool handlers *must be specified in the
+ same order for all processes* to ensure correct operation.
+
Use Cases
---------
--
2.13.6
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [dpdk-stable] [PATCH v2] doc: add multi-proc shared lib mempool note
2019-06-20 22:07 ` [dpdk-stable] [PATCH v2] " Gage Eads
@ 2019-07-04 20:53 ` Thomas Monjalon
0 siblings, 0 replies; 6+ messages in thread
From: Thomas Monjalon @ 2019-07-04 20:53 UTC (permalink / raw)
To: Gage Eads; +Cc: stable, dev, arybchenko, olivier.matz
21/06/2019 00:07, Gage Eads:
> The mempool library assigns handler ops indexes based on the dynamic load
> order of mempool handlers. Indexes are used so a mempool can be used by
> multiple processes, but this only works if all processes agree on the
> mapping from index to mempool handler.
>
> When using the '-d' argument, it's possible for different processes to load
> mempool handlers in different orders, and thus have different
> index->handler mappings. Using a mempool in multiple of such processes will
> result in undefined behavior.
>
> This commit adds a note to the mempool library programmer's guide warning
> users against this.
>
> Fixes: 449c49b93a6b ("mempool: support handler operations")
> Cc: stable@dpdk.org
>
> Signed-off-by: Gage Eads <gage.eads@intel.com>
> Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
Applied, thanks
^ permalink raw reply [flat|nested] 6+ messages in thread
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2019-06-18 18:48 [dpdk-stable] [PATCH] doc: add multi-proc shared lib mempool note Gage Eads
2019-06-20 18:01 ` Andrew Rybchenko
2019-06-20 19:07 ` Eads, Gage
2019-06-21 7:25 ` Andrew Rybchenko
2019-06-20 22:07 ` [dpdk-stable] [PATCH v2] " Gage Eads
2019-07-04 20:53 ` Thomas Monjalon
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