config: add Meson option for packet buffer headroom

The default value for RTE_PKTMBUF_HEADROOM used to be set in
config/rte_config.h. This patch removes it from the file and
instead, a Meson option, pkt_mbuf_headroom, is introduced to make
headroom tunable from the build process.

Signed-off-by: Parthakumar Roy <parthakumar.roy@ibm.com>

Author: Parthakumar Roy

.mailmap

@@ -1072,6 +1072,7 @@ Pankaj Gupta <pagupta@vmware.com> <pagupta@redhat.com>
 Panu Matilainen <pmatilai@redhat.com>
 Paolo Valerio <pvalerio@redhat.com>
 Parav Pandit <parav@nvidia.com> <parav@mellanox.com>
+Parthakumar Roy <parthakumar.roy@ibm.com>
 Pascal Mazon <pascal.mazon@6wind.com>
 Pashupati Kumar <kumarp@brocade.com>
 Patrice Buriez <patrice.buriez@intel.com>

config/meson.build

@@ -355,6 +355,7 @@ dpdk_conf.set('RTE_MAX_ETHPORTS', get_option('max_ethports'))
 dpdk_conf.set('RTE_LIBEAL_USE_HPET', get_option('use_hpet'))
 dpdk_conf.set('RTE_ENABLE_STDATOMIC', get_option('enable_stdatomic'))
 dpdk_conf.set('RTE_ENABLE_TRACE_FP', get_option('enable_trace_fp'))
+dpdk_conf.set('RTE_PKTMBUF_HEADROOM', get_option('pkt_mbuf_headroom'))
 # values which have defaults which may be overridden
 dpdk_conf.set('RTE_MAX_VFIO_GROUPS', 64)
 dpdk_conf.set('RTE_DRIVER_MEMPOOL_BUCKET_SIZE_KB', 64)

config/rte_config.h

@@ -62,7 +62,6 @@
 
 /* mbuf defines */
 #define RTE_MBUF_DEFAULT_MEMPOOL_OPS "ring_mp_mc"
-#define RTE_PKTMBUF_HEADROOM 128
 
 /* ether defines */
 #define RTE_MAX_QUEUES_PER_PORT 1024

meson_options.txt

@@ -50,6 +50,8 @@ option('mbuf_refcnt_atomic', type: 'boolean', value: true, description:
        'Atomically access the mbuf refcnt.')
 option('platform', type: 'string', value: 'native', description:
        'Platform to build, either "native", "generic" or a SoC. Please refer to the Linux build guide for more information.')
+option('pkt_mbuf_headroom', type: 'integer', value: 128, description:
+       'Default data offset (in bytes) in a packet buffer to leave room for additional headers.')
 option('enable_stdatomic', type: 'boolean', value: false, description:
        'enable use of C11 stdatomic')
 option('enable_trace_fp', type: 'boolean', value: false, description: