From: "Eads, Gage" <gage.eads@intel.com>
To: Andrew Rybchenko <arybchenko@solarflare.com>,
"dev@dpdk.org" <dev@dpdk.org>
Cc: "olivier.matz@6wind.com" <olivier.matz@6wind.com>,
"stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [dpdk-stable] [PATCH] doc: add multi-proc shared lib mempool note
Date: Thu, 20 Jun 2019 19:07:15 +0000 [thread overview]
Message-ID: <9184057F7FC11744A2107296B6B8EB1E68CFF97D@FMSMSX108.amr.corp.intel.com> (raw)
In-Reply-To: <381b4578-891f-5b1a-f2c4-38d73360f5d7@solarflare.com>
> -----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).
next prev parent reply other threads:[~2019-06-20 19:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-18 18:48 Gage Eads
2019-06-20 18:01 ` Andrew Rybchenko
2019-06-20 19:07 ` Eads, Gage [this message]
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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