Hi lads, > -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Bruce Richardson > Sent: Wednesday, February 18, 2015 9:36 AM > To: Olivier MATZ > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH 2/2] Remove RTE_MBUF_REFCNT references > > On Wed, Feb 18, 2015 at 10:16:56AM +0100, Olivier MATZ wrote: > > Hi Sergio, > > > > On 02/16/2015 05:08 PM, Sergio Gonzalez Monroy wrote: > > >This patch removes all references to RTE_MBUF_REFCNT, setting the refcnt > > >field in the mbuf struct permanently. > > > > > >Signed-off-by: Sergio Gonzalez Monroy <sergio.gonzalez.monroy at intel.com> > > > > I think removing the refcount compile option goes in the right > > direction. However, activating the refcount will break the applications > > that reserve a private zone in mbufs. This is due to the macros > > RTE_MBUF_TO_BADDR() and RTE_MBUF_FROM_BADDR() that suppose that > > the beginning of the mbuf is 128 bytes (sizeof mbuf) before the > > data buffer. > > > > While I understand how the macros make certain assumptions, how does > activating > the refcnt specifically lead to the problems you describe? Could you explain > that part in a bit more detail? > > Thanks, > /Bruce >
Olivier, I also don't understand your concern here. As I can see, that patch has nothing to do with RTE_MBUF_FROM_BADDR/ RTE_MBUF_FROM_BADDR macros. They are still there, for example rte_pktmbuf_detach() still uses it to restore mbuf's buf_addr. The only principal change here, is that we don't rely more on RTE_MBUF_FROM_BADDR to determine, Is that indirect mbuf or not. Instead we use a special falg for that purpose: -#define RTE_MBUF_INDIRECT(mb) (RTE_MBUF_FROM_BADDR((mb)->buf_addr) != (mb)) +#define RTE_MBUF_INDIRECT(mb) (mb->ol_flags & IND_ATTACHED_MBUF) BTW, Sergio as I said before, I think it should be: #define RTE_MBUF_INDIRECT(mb) ((mb)->ol_flags & IND_ATTACHED_MBUF) Konstantin > > For RTE_MBUF_TO_BADDR(), it's relatively easy to replace it. The > > mbuf pool could store the size of the private size like it's done > > for mbp_priv->mbuf_data_room_size. Using rte_mempool_from_obj(m) > > or m->pool, we can retrieve the mbuf pool and this value, then > > compute the buffer address. > > > > For RTE_MBUF_FROM_BADDR(), it's more complex. We could ensure that > > a backpointer to the mbuf is always located before the data buffer, > > but it looks difficult to do. > > > > Another idea would be to add a field in indirect mbufs that stores > > the pointer to the "parent" mbuf. > > > > Regards, > > Olivier > >
