[dpdk-dev] [PATCH 2/2] build: find max lcore programmatically

[Dharmik Thakkar]

For Arm, RTE_MAX_LCORE is hard-coded into the config. It leads to incorrect
RTE_MAX_LCORE when machines have same Implemener and part number
but different number of CPUs.
For x86, RTE_MAX_LCORE is always set to 128 (using the value
set in meson_options.txt)

Use python script to find max lcore when using native build to
correctly set RTE_MAX_LCORE.

Signed-off-by: Dharmik Thakkar <dharmik.thakkar at arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
---
 config/get_max_lcores.py | 13 +++++++++++++
 config/meson.build       | 13 ++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100755 config/get_max_lcores.py

diff --git a/config/get_max_lcores.py b/config/get_max_lcores.py
new file mode 100755
index 000000000000..ebf1c7efdadd
--- /dev/null
+++ b/config/get_max_lcores.py
@@ -0,0 +1,13 @@
+#!/usr/bin/python3
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright(c) 2020 Arm Limited
+
+import os
+
+max_lcores = []
+
+nCPU = os.cpu_count()
+
+max_lcores.append(str(nCPU & 0xFFF))             # Number of CPUs
+
+print(' '.join(max_lcores))
diff --git a/config/meson.build b/config/meson.build
index 6996e5cbeaa5..80c05bc15d2f 100644
--- a/config/meson.build
+++ b/config/meson.build
@@ -237,11 +237,22 @@ else # for 32-bit we need smaller reserved memory areas
 	dpdk_conf.set('RTE_MAX_MEM_MB', 2048)
 endif
 
-
 compile_time_cpuflags = []
 subdir(arch_subdir)
 dpdk_conf.set('RTE_COMPILE_TIME_CPUFLAGS', ','.join(compile_time_cpuflags))
 
+# set max lcores
+if machine != 'default' and not meson.is_cross_build()
+	# The script returns max lcores
+	params = files('get_max_lcores.py')
+	cmd_out = run_command(params)
+	if cmd_out.returncode() == 0
+		cmd_lcore = cmd_out.stdout().to_lower().strip().split(' ')
+	endif
+	max_lcore = cmd_lcore[0].to_int()
+	dpdk_conf.set('RTE_MAX_LCORE', max_lcore)
+endif
+
 # set the install path for the drivers
 dpdk_conf.set_quoted('RTE_EAL_PMD_PATH', eal_pmd_path)
 
-- 
2.17.1