[dpdk-dev] [EXT] Default cacheline size for ARM

[Jerin Jacob Kollanukkaran]

On Fri, 2019-01-18 at 05:50 +0000, Honnappa Nagarahalli wrote:
> > > > > > > > Hi,
> > > > > > > > 
> > > > > > > > The cacheline size (RTE_CACHE_LINE_SIZE) for ARM CPUs
> > > > > > > > is set
> > > > > > > > to be 128B by default. Mellanox's BlueField is an ARM
> > > > > > > > CPU
> > > > > > > > having
> > > > > > > > Cortex-A72
> > > > > > > > and its CL size is 64B.
> > > > > > Just wondering how many devices are out there with 128B
> > > > > > cache
> > > > > > line? I also have not heard about any future devices with
> > > > > > 128B
> > > > > > cache line. If the majority is 64B, why not keep 64B as the
> > > > > > default?
> > > > > 
> > > > > The problem is, In the armv8 spec the cache line size is
> > > > > IMPLEMENTATION DEFINED. Marvell's embedded processors has
> > > > > 128B
> > CL
> > > > > and Server processors has 64B CL.
> > > > > 
> > > > > Assuming the defconfig_arm64-armv8a-linuxapp-gcc will be used
> > > > > by
> > > > > distro folks then that configuration should support all the
> > > > > devices with
> > > > > armv8.1 spec. For instance, marvells new chips are armv8.2
> > > > > but we
> > > > > can not make that as default.
> > > > What will happen in the future when we will have v9, v10 etc? I
> > > > think the distro(generic/binary portable) config should get rid
> > > > of v8.
> > > 
> > > Will it be too much overhead if the image is same for v8, v9 and
> > > v10.
> > > I think, we can inline with what distro folks are doing for other
> > > packages, I think, DPDK package does not need any exception.
> > Yes, we need to be inline with any other package. My understanding
> > is that
> > the image will be same for v8,v9,v10 (any input from distro
> > engineers will
> > help here). So, my question is, should the config file/name used by
> > distros
> > contain anything specific to armv8?
> Jerin, after following [1], I am not unable to understand when the
> file config/arm/arm64_armv8_linuxapp_gcc gets used. Is this file
> required?

If I understand it correctly, only for cross compiling on x86.
distro folks build the generic image on arm64 with -Dmachine=default
for arm64.


> 
> 1. http://mails.dpdk.org/archives/dev/2019-January/123272.html