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From: Neil Horman <nhorman@tuxdriver.com>
To: Bruce Richardson <bruce.richardson@intel.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 4/5] mbuf: add userdata pointer field
Date: Wed, 17 Sep 2014 11:35:10 -0400
Message-ID: <20140917153510.GG4213@localhost.localdomain> (raw)
In-Reply-To: <1410948102-12740-5-git-send-email-bruce.richardson@intel.com>

On Wed, Sep 17, 2014 at 11:01:41AM +0100, Bruce Richardson wrote:
> While some applications may store metadata about packets in the packet
> mbuf headroom, this is not a workable solution for packet metadata which
> is either:
> * larger than the headroom (or headroom is needed for adding pkt headers)
> * needs to be shared or copied among packets
> 
> To support these use cases in applications, we reserve a general
> "userdata" pointer field inside the second cache-line of the mbuf. This
> is better than having the application store the pointer to the external
> metadata in the packet headroom, as it saves an additional cache-line
> from being used.
> 
> Apart from storing metadata, this field also provides a general 8-byte
> scratch space inside the mbuf for any other application uses that are
> applicable.
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> ---
>  lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h | 3 ++-
>  lib/librte_mbuf/rte_mbuf.h                                    | 3 +++
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h b/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h
> index 25ed672..d27e891 100644
> --- a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h
> +++ b/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h
> @@ -117,7 +117,8 @@ struct rte_kni_mbuf {
>  	uint16_t data_len;      /**< Amount of data in segment buffer. */
>  	uint32_t pkt_len;       /**< Total pkt len: sum of all segment data_len. */
>  	char pad3[8];
> -	void *pool __attribute__((__aligned__(64)));
> +	void *pad4 __attribute__((__aligned__(64)));
> +	void *pool;
I don't see a comment about this in the changelog, only about the userdata
pointer being added below.


>  	void *next;
>  };
>  
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 8e27d2e..b1acfc3 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -172,6 +172,9 @@ struct rte_mbuf {
>  
>  	/* second cache line - fields only used in slow path or on TX */
>  	MARKER cacheline1 __rte_cache_aligned;
> +
> +	void *userdata;           /**< Can be used for external metadata */
> +
Do you want to make this a void* or a char[8]?  I ask because if people are
going to use is as a scratch space (rather than a pointer), they get a suprise
when they build this on 32 bit systems, and their 8 byte scratch space is
reduced to 4 bytes.

Neil

>  	struct rte_mempool *pool; /**< Pool from which mbuf was allocated. */
>  	struct rte_mbuf *next;    /**< Next segment of scattered packet. */
>  
> -- 
> 1.9.3
> 
> 

  reply	other threads:[~2014-09-17 15:29 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-17 10:01 [dpdk-dev] [PATCH 0/5] Mbuf Structure Rework, part 3 Bruce Richardson
2014-09-17 10:01 ` [dpdk-dev] [PATCH 1/5] mbuf: ensure next pointer is set to null on free Bruce Richardson
2014-09-17 10:01 ` [dpdk-dev] [PATCH 2/5] ixgbe: add prefetch to improve slow-path tx perf Bruce Richardson
2014-09-17 15:21   ` Neil Horman
2014-09-17 15:35     ` Richardson, Bruce
2014-09-17 17:59       ` Neil Horman
2014-09-18 13:36         ` Bruce Richardson
2014-09-18 15:29           ` Neil Horman
2014-09-18 15:42             ` Bruce Richardson
2014-09-18 17:56               ` Neil Horman
2014-09-17 10:01 ` [dpdk-dev] [PATCH 3/5] testpmd: Change rxfreet default to 32 Bruce Richardson
2014-09-17 15:29   ` Neil Horman
2014-09-18 15:53     ` Richardson, Bruce
2014-09-18 17:13       ` Thomas Monjalon
2014-09-18 18:08         ` Neil Horman
2014-09-19  9:18           ` Richardson, Bruce
2014-09-19 10:24             ` Neil Horman
2014-09-19 10:28               ` Richardson, Bruce
2014-09-19 15:18                 ` Neil Horman
2014-09-18 18:03       ` Neil Horman
2014-09-17 10:01 ` [dpdk-dev] [PATCH 4/5] mbuf: add userdata pointer field Bruce Richardson
2014-09-17 15:35   ` Neil Horman [this message]
2014-09-17 16:02     ` Richardson, Bruce
2014-09-17 18:29       ` Neil Horman
2014-09-17 10:01 ` [dpdk-dev] [PATCH 5/5] mbuf: Add in second vlan tag field to mbuf Bruce Richardson
2014-09-17 20:46   ` Stephen Hemminger
2014-09-23 11:08 ` [dpdk-dev] [PATCH v2 0/5] Mbuf Structure Rework, part 3 Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 1/5] mbuf: ensure next pointer is set to null on free Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 2/5] ixgbe: add prefetch to improve slow-path tx perf Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 3/5] testpmd: Change rxfreet default to 32 Bruce Richardson
2014-09-23 17:02     ` Neil Horman
2014-09-24  9:03       ` Richardson, Bruce
2014-09-24 10:05         ` Neil Horman
2014-11-07 12:30         ` Thomas Monjalon
2014-11-07 13:49           ` Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 4/5] mbuf: add userdata pointer field Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 5/5] mbuf: switch vlan_tci and reserved2 fields Bruce Richardson
2014-09-29 15:58   ` [dpdk-dev] [PATCH v2 0/5] Mbuf Structure Rework, part 3 De Lara Guarch, Pablo
2014-10-08 12:31     ` Thomas Monjalon

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