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

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

Hi Olivier,

If fails to compile for me:

/local/kananye1/dpdk.org-mbprv1/lib/librte_mbuf/rte_mbuf.c: In function ârte_pktmbuf_pool_createâ:
/local/kananye1/dpdk.org-mbprv1/lib/librte_mbuf/rte_mbuf.c:161:3: error: ârte_errnoâ undeclared (first use in this function)
   rte_errno = EINVAL;
   ^
/local/kananye1/dpdk.org-mbprv1/lib/librte_mbuf/rte_mbuf.c:161:3: note: each undeclared identifier is reported only once for each function it appears in

I had to add:

diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
index a1ddbb3..04344c0 100644
--- a/lib/librte_mbuf/rte_mbuf.c
+++ b/lib/librte_mbuf/rte_mbuf.c
@@ -58,6 +58,7 @@
 #include <rte_mbuf.h>
 #include <rte_string_fns.h>
 #include <rte_hexdump.h>
+#include <rte_errno.h>

 /*
  * ctrlmbuf constructor, given as a callback function to

Apart from that - looks good to me.
Konstantin
 
> -----Original Message-----
> From: Olivier Matz [mailto:olivier.matz@6wind.com]
> Sent: Thursday, July 30, 2015 2:56 PM
> To: dev@dpdk.org
> Cc: Ananyev, Konstantin; olivier.matz@6wind.com; Zhang, Helin; martin.weiser@allegro-packets.com; thomas.monjalon@6wind.com
> Subject: [PATCH] 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>
> ---
>  lib/librte_eal/common/include/rte_log.h | 1 +
>  lib/librte_mbuf/rte_mbuf.c              | 8 +++++++-
>  lib/librte_mbuf/rte_mbuf.h              | 7 +++++--
>  3 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_eal/common/include/rte_log.h b/lib/librte_eal/common/include/rte_log.h
> index 24a55cc..ede0dca 100644
> --- a/lib/librte_eal/common/include/rte_log.h
> +++ b/lib/librte_eal/common/include/rte_log.h
> @@ -77,6 +77,7 @@ extern struct rte_logs rte_logs;
>  #define RTE_LOGTYPE_PORT    0x00002000 /**< Log related to port. */
>  #define RTE_LOGTYPE_TABLE   0x00004000 /**< Log related to table. */
>  #define RTE_LOGTYPE_PIPELINE 0x00008000 /**< Log related to pipeline. */
> +#define RTE_LOGTYPE_MBUF    0x00010000 /**< Log related to mbuf. */
> 
>  /* these log types can be used in an application */
>  #define RTE_LOGTYPE_USER1   0x01000000 /**< User-defined log type 1. */
> diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
> index 4320dd4..a1ddbb3 100644
> --- a/lib/librte_mbuf/rte_mbuf.c
> +++ b/lib/librte_mbuf/rte_mbuf.c
> @@ -125,6 +125,7 @@ rte_pktmbuf_init(struct rte_mempool *mp,
>  	mbuf_size = sizeof(struct rte_mbuf) + priv_size;
>  	buf_len = rte_pktmbuf_data_room_size(mp);
> 
> +	RTE_MBUF_ASSERT((priv_size & (RTE_MBUF_PRIV_ALIGN - 1)) == 0);
>  	RTE_MBUF_ASSERT(mp->elt_size >= mbuf_size);
>  	RTE_MBUF_ASSERT(buf_len <= UINT16_MAX);
> 
> @@ -154,7 +155,12 @@ rte_pktmbuf_pool_create(const char *name, unsigned n,
>  	struct rte_pktmbuf_pool_private mbp_priv;
>  	unsigned elt_size;
> 
> -
> +	if ((priv_size & (RTE_MBUF_PRIV_ALIGN - 1)) != 0) {
> +		RTE_LOG(ERR, MBUF, "mbuf priv_size=%u is not aligned\n",
> +			priv_size);
> +		rte_errno = EINVAL;
> +		return NULL;
> +	}
>  	elt_size = sizeof(struct rte_mbuf) + (unsigned)priv_size +
>  		(unsigned)data_room_size;
>  	mbp_priv.mbuf_data_room_size = data_room_size;
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 010b32d..c3b8c98 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -698,6 +698,9 @@ extern "C" {
>                                                   RTE_PTYPE_INNER_L4_MASK))
>  #endif /* RTE_NEXT_ABI */
> 
> +/** Alignment constraint of mbuf private area. */
> +#define RTE_MBUF_PRIV_ALIGN 8
> +
>  /**
>   * Get the name of a RX offload flag
>   *
> @@ -1238,7 +1241,7 @@ void rte_pktmbuf_pool_init(struct rte_mempool *mp, void *opaque_arg);
>   *   details.
>   * @param priv_size
>   *   Size of application private are between the rte_mbuf structure
> - *   and the data buffer.
> + *   and the data buffer. This value must be aligned to RTE_MBUF_PRIV_ALIGN.
>   * @param data_room_size
>   *   Size of data buffer in each mbuf, including RTE_PKTMBUF_HEADROOM.
>   * @param socket_id
> @@ -1250,7 +1253,7 @@ void rte_pktmbuf_pool_init(struct rte_mempool *mp, void *opaque_arg);
>   *   with rte_errno set appropriately. Possible rte_errno values include:
>   *    - E_RTE_NO_CONFIG - function could not get pointer to rte_config structure
>   *    - E_RTE_SECONDARY - function was called from a secondary process instance
> - *    - EINVAL - cache size provided is too large
> + *    - EINVAL - cache size provided is too large, or priv_size is not aligned.
>   *    - ENOSPC - the maximum number of memzones has already been allocated
>   *    - EEXIST - a memzone with the same name already exists
>   *    - ENOMEM - no appropriate memory area found in which to create memzone
> --
> 2.1.4