Re: [dpdk-dev] [PATCH 1/2] config: add Graviton2(arm64) meson configuration

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

<snip>

> 
> On 9/11/20 8:23 PM, Honnappa Nagarahalli wrote:
> >
> > +Jerin, Hemant, Dharmik
> >
> > <snip>
> > Hi Vimal,
> >         Few comments inline.
> >
> >>
> >> Add meson build configuration for Graviton2 platform with 64-bit ARM
> >> Neoverse N1 cores. This patch makes the following changes to generic
> >> Neoverse N1 config:
> >>
> >> 1. increase lcore limit to 64
> >> 2. increase memory support to 1TB
> > There will be multiple SoCs with N1 cores. All of them will have the same
> implementor ID and part number. But, they will have different values for
> these configurable parameters.
> > IMO, from usage perspective, we have 2 cases:
> > 1) Ability to build a portable binary that can run on multiple Arm
> > SoCs (for ex: BlueField, thunderx1, thunderx2, N1SDP, Graviton2 etc)
> > 2) Ability to build a binary which would run only on a SoC it was compiled
> for and provide the most optimized binary for that SoC. But, this may not be
> portable.
> >
> > For 1) we have default march.
> >
> > For 2) we do not have the capability today in meson build (at least, this is
> my understanding, please correct me if I am wrong). In this case, the user
> knows the target platform for compilation. IMO, we should add the capability
> to take the target platform as an input from the user (similar to the make
> build system) and Graviton2 can be one such target platform.
> 
> My intention was to have parameters that work for both N1SDP and
> Graviton2 rather than 2). Does the change to RTE_MAX_LCORE and
> RTE_MAX_MEM_MB make them incompatible with N1SDP?
They are not optimal for N1SDP. In the future these parameters might have to be changed. For ex: if there a N1 based SoC with more than 64 CPU cores.

> 
> I'm not sure if taking target platform from user is the best option here.
> Would this be specific to N1 since other platforms like thunderx differentiate
> the flags with part number?
This issue is specific to Arm CPU cores in general. So, it applies to N1 too.

> 
> >
> >> 3. remove +crc from -march as that is default when setting armv8.2
> >>
> >> For more information about Graviton2 platform, refer to:
> >> https://aws.amazon.com/ec2/graviton/
> >>
> >> Signed-off-by: Vimal Chungath <vcchunga@amazon.com>
> >> ---
> >>  config/arm/arm64_graviton2_linux_gcc | 17 +++++++++++++++++
> >>  config/arm/meson.build               | 12 +++++++++++-
> >>  2 files changed, 28 insertions(+), 1 deletion(-)  create mode 100644
> >> config/arm/arm64_graviton2_linux_gcc
> >>
> >> diff --git a/config/arm/arm64_graviton2_linux_gcc
> >> b/config/arm/arm64_graviton2_linux_gcc
> >> new file mode 100644
> >> index 000000000..022e06303
> >> --- /dev/null
> >> +++ b/config/arm/arm64_graviton2_linux_gcc
> >> @@ -0,0 +1,17 @@
> >> +[binaries]
> >> +c = 'aarch64-linux-gnu-gcc'
> >> +cpp = 'aarch64-linux-gnu-cpp'
> >> +ar = 'aarch64-linux-gnu-gcc-ar'
> >> +strip = 'aarch64-linux-gnu-strip'
> >> +pkgconfig = 'aarch64-linux-gnu-pkg-config'
> >> +pcap-config = ''
> >> +
> >> +[host_machine]
> >> +system = 'linux'
> >> +cpu_family = 'aarch64'
> >> +cpu = 'armv8-a'
> >> +endian = 'little'
> >> +
> >> +[properties]
> >> +implementor_id = '0x41'
> >> +implementor_pn = '0xd0c'
> >> diff --git a/config/arm/meson.build b/config/arm/meson.build index
> >> 8728051d5..64e277ebc 100644
> >> --- a/config/arm/meson.build
> >> +++ b/config/arm/meson.build
> >> @@ -86,6 +86,16 @@ flags_octeontx2_extra = [
> >>       ['RTE_ARM_FEATURE_ATOMICS', true],
> >>       ['RTE_EAL_IGB_UIO', false],
> >>       ['RTE_USE_C11_MEM_MODEL', true]]
> >> +flags_n1generic_extra = [
> >> +     ['RTE_MACHINE', '"neoverse-n1"'],
> >> +     ['RTE_MAX_LCORE', 64],
> >> +     ['RTE_CACHE_LINE_SIZE', 64],
> >> +     ['RTE_ARM_FEATURE_ATOMICS', true],
> >> +     ['RTE_USE_C11_MEM_MODEL', true],
> >> +     ['RTE_MAX_MEM_MB', 1048576],
> >> +     ['RTE_MAX_NUMA_NODES', 1],
> >> +     ['RTE_EAL_NUMA_AWARE_HUGEPAGES', false],
> >> +     ['RTE_LIBRTE_VHOST_NUMA', false]]
> >>
> >>  machine_args_generic = [
> >>       ['default', ['-march=armv8-a+crc']], @@ -97,7 +107,7 @@
> >> machine_args_generic = [
> >>       ['0xd09', ['-mcpu=cortex-a73']],
> >>       ['0xd0a', ['-mcpu=cortex-a75']],
> >>       ['0xd0b', ['-mcpu=cortex-a76']],
> >> -     ['0xd0c', ['-march=armv8.2-a+crc+crypto', '-mcpu=neoverse-n1'],
> >> flags_n1sdp_extra]]
> >> +     ['0xd0c', ['-march=armv8.2-a+crypto', '-mcpu=neoverse-n1'],
> >> +flags_n1generic_extra]]
> >>
> >>  machine_args_cavium = [
> >>       ['default', ['-march=armv8-a+crc+crypto','-mcpu=thunderx']],
> >> --
> >> 2.16.6
> >