Re: [dpdk-dev] [PATCH v5 0/2] Balanced allocation of hugepages

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Wed, 21 Jun 2017 10:49:14 +0200
> From: Thomas Monjalon <thomas@monjalon.net>
> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> Cc: Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>, Hemant
>  Agrawal <hemant.agrawal@nxp.com>, Ilya Maximets <i.maximets@samsung.com>,
>  dev@dpdk.org, Bruce Richardson <bruce.richardson@intel.com>, David
>  Marchand <david.marchand@6wind.com>, Heetae Ahn
>  <heetae82.ahn@samsung.com>, Yuanhan Liu <yliu@fridaylinux.org>, Jianfeng
>  Tan <jianfeng.tan@intel.com>, Neil Horman <nhorman@tuxdriver.com>, Yulong
>  Pei <yulong.pei@intel.com>
> Subject: Re: [PATCH v5 0/2] Balanced allocation of hugepages
> 
> 21/06/2017 10:41, Jerin Jacob:
> > > > 1. There are many machines (arm/ppc), which do not support NUMA.
> > > > 
> > > > https://wiki.linaro.org/LEG/Engineering/Kernel/NUMA
> > > > 
> > > 
> > > I did find that link too, last modified 4 years ago.
> > > Despite that, I could not find any ARM references in libnuma sources, but
> > > Jerin proved that there is support for it.
> > > 
> > > http://oss.sgi.com/projects/libnuma/
> > > https://github.com/numactl/numactl
> > 
> > Those Linaro links are very old. ARM64 NUMA supported has been added in 4.7 kernel.
> > I guess we are talking about build time time dependency with libnuma here.
> > Correct? I think, Even with old arm64 kernel(< 4.6), You can build against
> > libnuma if it is present in rootfs. Just that at runtime, it will return
> > NUMA support not available. Correct?
> > 
> > How hard is detect the presence of "numaif.h" if existing build system does not
> > support it? If it trivial, we can enable RTE_LIBRTE_EAL_NUMA_AWARE_HUGEPAGES
> > if build environment has "numaif.h".
> > 
> > Some example in linux kernel build system:
> > http://lxr.linux.no/linux+v4.10.1/scripts/gcc-goto.sh
> 
> I think we should not try to detect numaif.h, because it should be
> an error on platform supporting NUMA.

I have installed libnuma on a NUMA and non NUMA machine.
Compiled and ran following code on those machine and it could detect
the numa availability. Could you add more details on the "error on
platform supporting NUMA".

➜ 83xx [ctest] $ cat main.c
#include <numaif.h>
#include <stdio.h>
#include <errno.h>

int main()
{
        /* Check if kernel supports NUMA. */
        if (get_mempolicy(NULL, NULL, 0, 0, 0) < 0 && errno == ENOSYS) {
                printf("NUMA is not supported.\n");
        } else {
                printf("NUMA is supported.\n");
        }

}
➜ 83xx [ctest] $ gcc -Wall main.c -lnuma
# On non numa system
➜ 83xx [ctest] $ ./a.out
NUMA is not supported

# On numa machine
➜ GB-2S [~] $ ./a.out
NUMA is supported.


> If someone really wants to build DPDK without NUMA for x86, he should
> disable it in the build config file.