[RFC] config: customize max memzones configuration

[Ophir Munk <ophirmu@nvidia.com>]

In current DPDK the RTE_MAX_MEMZONE definition is unconditionally hard
coded as 2560.  For applications requiring different values of this
parameter – it is more convenient to set its value as part of the meson
command line or to set the max value via an rte API - rather than
changing the dpdk source code per application.

An example would be of an application that uses the DPDK mempool library
which is based on DPDK memzone library.  The application may need to
create a number of steering tables, each of which will require its own
mempool allocation.  This RFC is not about how to optimize the
application usage of mempool nor about how to improve the mempool
implementation based on memzone.  It is about how to make the max
memzone definition - build-time or run-time customized.

I would like to suggest three options.

Option 1
========
Add a Meson option in meson options.txt and remove the
RTE_MAX_MEMZONE definition from config/rte_config.h

For example,

 config/meson.build

 # set other values pulled from the build options
 dpdk_conf.set('RTE_MAX_LCORE', get_option('max_lcores'))
 +dpdk_conf.set('RTE_MAX_MEMZONE', get_option('max_memzones'))
 dpdk_conf.set('RTE_MAX_NUMA_NODES', get_option('max_numa_nodes'))

 meson_options.txt

 option('max_lcores', type: 'integer', value: 128,
        description: 'maximum number of cores/threads supported by EAL')
 +option('max_memzones', type: 'integer', value: 2560,
 +       description: 'maximum number of memory zones supported by EAL')
 option('max_numa_nodes', type: 'integer', value: 32,
        description: 'maximum number of NUMA nodes supported by EAL')

 config/rte_config.h

 #define RTE_MAX_MEM_MB_PER_TYPE 65536
 -#define RTE_MAX_MEMZONE 2560
 #define RTE_MAX_TAILQ 32

Option 2
========
Use Meson setup -Dc_args="-DRTE_MAX_MEMZONE=XXX" and
make RTE_MAX_MEMZONE conditional in config/rte_config.h

For example, see the code of this commit.

Option 3
========
Add a function which must be called before rte_eal_init():
void rte_memzone_set_max(int max) {memzone_max = max;}
If not called, the default memzone (RTE_MAX_MEMZONE) is used.

With this option there is no need to recompile DPDK and it allows
using an in-box packaged DPDK.

Signed-off-by: Ophir Munk <ophirmu@nvidia.com>
---
 config/rte_config.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/config/rte_config.h b/config/rte_config.h
index fed174a..ca653cc 100644
--- a/config/rte_config.h
+++ b/config/rte_config.h
@@ -35,7 +35,9 @@
 #define RTE_MAX_MEM_MB_PER_LIST 32768
 #define RTE_MAX_MEMSEG_PER_TYPE 32768
 #define RTE_MAX_MEM_MB_PER_TYPE 65536
+#ifndef RTE_MAX_MEMZONE
 #define RTE_MAX_MEMZONE 2560
+#endif
 #define RTE_MAX_TAILQ 32
 #define RTE_LOG_DP_LEVEL RTE_LOG_INFO
 #define RTE_BACKTRACE 1
-- 
2.8.4