Re: [dpdk-dev] [PATCH] ixgbe: Fix compilation issue in vpmd

["Doherty, Declan" <declan.doherty@intel.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas Monjalon
> Sent: Tuesday, October 21, 2014 9:36 AM
> To: Ouyang, Changchun; De Lara Guarch, Pablo
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] ixgbe: Fix compilation issue in vpmd
> 
> 2014-10-21 08:28, Ouyang, Changchun:
> > From: De Lara Guarch, Pablo
> > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas Monjalon
> > > > 2014-10-21 14:59, Ouyang Changchun:
> > > > > Fix the compilation issue in vector PMD when macro RTE_MBUF_REFCNT
> > > > > is disabled.
> > > > >
> > > > > Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
> > > >
> > > > Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>
> > > >
> > > > Applied
> > >
> > > I was checking this patch right now, and I come across a second compilation
> > > issue,  because rte_mbuf_refcnt_update and rte_pktmbuf_attach are not
> > > declared, and Bond PMD and IP fragmentation libraries use those functions.
> > >
> > > I guess that it is late to NACK this :P, but we require a second patch to fix
> > > completely this issue.
> >
> > As it fixes the compilation issue in vpmd, so no reason to NACK it,  :-)
> 
> Exact
> 
> > In my config, both BOND and IP fragment is disabled. So I don't come across your
> issues.
> > Yes, agree with you, we need another patch to fix compilation issue in other
> both places.
> 
> Yes, I'm aware of these limitations.
> Please, first explain why mbuf refcnt is needed for these features.
> Then we have 2 options: remove the dependency or add more ifdefs.
> 
> Thanks
> --
> Thomas

Thomas, 
for link bonding the refcnt is used in broadcast mode to allow the same
mbuf to be transmitted on multiple slaves. By increasing the refcnt, we 
can safely transmit the mbuf on multiple slaves without the danger of a 
mbuf being freed by one slave while in use by another. I can provide a patch to
disable the broadcast mode of operation if the bonding pmd is built with the macro 
RTE_MBUF_REFCNT disabled. I don't think there is any other option other than 
than to completely disable the library if the refcnt parameter isn't available
as we don't have access to the transmit mempool to allocate new mbufs to
make copies of the original. 

Declan