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

[Dharmik Thakkar <Dharmik.Thakkar@arm.com>]

> On Sep 3, 2020, at 1:20 AM, Juraj Linkeš <juraj.linkes@pantheon.tech> wrote:
> 
> 
> 
>> -----Original Message-----
>> From: dev <dev-bounces@dpdk.org> On Behalf Of Dharmik Thakkar
>> Sent: Wednesday, August 26, 2020 6:56 AM
>> To: Jerin Jacob <jerinjacobk@gmail.com>
>> Cc: thomas@monjalon.net; dpdk-dev <dev@dpdk.org>; nd <nd@arm.com>
>> Subject: Re: [dpdk-dev] [PATCH 2/2] build: find max lcore programmatically
>> 
>> 
>> 
>>> On Aug 25, 2020, at 11:47 PM, Jerin Jacob <jerinjacobk@gmail.com> wrote:
>>> 
>>> On Wed, Aug 26, 2020 at 2:44 AM Dharmik Thakkar
>> <dharmik.thakkar@arm.com> wrote:
>>>> 
>>>> 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.
>>> 
>>> We may need to build on the native arm64 machine and use it on another
>>> arm64 machine(Just like x86).
>>> So I think, at least for default config(which will be used by
>>> distribution) to support max
>>> lcores as fixed. I am not sure this patch changes those aspects or
>>> not? Please check.
>> 
>> This patch does *not* affect ‘default’ build type and cross-compilation.
>> 
>>> 
>>>> 
>>>> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
>>>> Reviewed-by: Ruifeng Wang <ruifeng.wang@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)
> 
> Have you considered running just a shell command, such as "nproc --all"?

Shell command based solution such as “nproc —all” is not OS-agnostic, it doesn’t work on Windows.

> 
>>>> +       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