Re: [dpdk-dev] [PATCH v2] mbuf: enforce alignment of mbuf private area

["Zhang, Helin" <helin.zhang@intel.com>]

> -----Original Message-----
> From: Olivier Matz [mailto:olivier.matz@6wind.com]
> Sent: Thursday, July 30, 2015 9:22 AM
> To: dev@dpdk.org
> Cc: Ananyev, Konstantin; olivier.matz@6wind.com; Zhang, Helin;
> martin.weiser@allegro-packets.com; thomas.monjalon@6wind.com
> Subject: [PATCH v2] mbuf: enforce alignment of mbuf private area
> 
> It looks better to have a data buffer address that is aligned to
> 8 bytes. This is the case when there is no mbuf private area, but if there is one,
> the alignment depends on the size of this area that is located between the mbuf
> structure and the data buffer.
> 
> Indeed, some drivers expects to have the buffer address aligned to an even
> address, and moreover an unaligned buffer may impact the performance when
> accessing to network headers.
> 
> Add a check in rte_pktmbuf_pool_create() to verify the alignment constraint
> before creating the mempool. For applications that use the alternative way
> (direct call to rte_mempool_create), also add an assertion in rte_pktmbuf_init().
> 
> By the way, also add the MBUF log type.
> 
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Helin Zhang <helin.zhang@intel.com>