> On Sep 17, 2020, at 4:56 AM, Juraj Linkeš <juraj.lin...@pantheon.tech> wrote:
>
>
>
>> -----Original Message-----
>> From: Dharmik Thakkar <dharmik.thak...@arm.com>
>> Sent: Friday, September 4, 2020 7:44 AM
>> To: Stephen Hemminger <step...@networkplumber.org>
>> Cc: Juraj Linkeš <juraj.lin...@pantheon.tech>; Jerin Jacob
>> <jerinjac...@gmail.com>; tho...@monjalon.net; dpdk-dev <dev@dpdk.org>;
>> nd <n...@arm.com>
>> Subject: Re: [dpdk-dev] [PATCH 2/2] build: find max lcore programmatically
>>
>>
>>
>>> On Sep 3, 2020, at 5:52 PM, Stephen Hemminger
>> <step...@networkplumber.org> wrote:
>>>
>>> On Thu, 3 Sep 2020 06:20:17 +0000
>>> Juraj Linkeš <juraj.lin...@pantheon.tech> wrote:
>>>
>>>>> -----Original Message-----
>>>>> From: dev <dev-boun...@dpdk.org> On Behalf Of Dharmik Thakkar
>>>>> Sent: Wednesday, August 26, 2020 6:56 AM
>>>>> To: Jerin Jacob <jerinjac...@gmail.com>
>>>>> Cc: tho...@monjalon.net; dpdk-dev <dev@dpdk.org>; nd <n...@arm.com>
>>>>> Subject: Re: [dpdk-dev] [PATCH 2/2] build: find max lcore
>>>>> programmatically
>>>>>
>>>>>
>>>>>
>>>>>> On Aug 25, 2020, at 11:47 PM, Jerin Jacob <jerinjac...@gmail.com>
>> wrote:
>>>>>>
>>>>>> On Wed, Aug 26, 2020 at 2:44 AM Dharmik Thakkar
>>>>> <dharmik.thak...@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.thak...@arm.com>
>>>>>>> Reviewed-by: Ruifeng Wang <ruifeng.w...@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"?
>>>
>>> Is this really a good idea?
>>> For real distributions and NFV products, the build and runtime
>>> environment will usually be different even if on same CPU architecture.
>>>
>>> In many cases there maybe a huge build machine (128 CPU) or in a
>>> container (reported as single cpu) even if not doing cross build.
>>
>> That’s a great point, Stephen. IMO, this patch is useful when building and
>> running natively.
>> For all other purposes (like the ones you mentioned), do you think it is a
>> good
>> idea to set RTE_MAX_LCORE using -Dmax_lcores?
>
> We should only use this native builds, as that would be consistent with the
> current meson build philosophy of "meson figuring as much as possible on its
> own". Any build other than native implies the user wants to deviate from the
> build machine.
>
The MIDR value-based probing doesn’t quite work well for Arm IP (currently
being discussed on this patch: https://patches.dpdk.org/patch/76981/).
> One way to do this automatic core count is when max_lcores=0 (0 would have
> the special meaning of "figure core count automatically"). We can set that as
> default in meson_option.txt and then users will have the ability to set it to
> whatever they want, even for native builds. What do you think?
>
Yes, agreed.
> Currently the -Dmax_lcores option doesn't work for arm builds (the value of
> RTE_MAX_LCORE is overwritten in config/arm/meson.build). I believe the patch
> tries to address this, but still, we need to be mindful of that.
>
> Juraj
