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

-----Original Message-----

Date: Wed, 21 Jun 2017 10:49:14 +0200
From: Thomas Monjalon <redacted>
To: Jerin Jacob <redacted>
Cc: Sergio Gonzalez Monroy <redacted>, Hemant
 Agrawal [off-list ref], Ilya Maximets [off-list ref],
 dev@dpdk.org, Bruce Richardson [off-list ref], David
 Marchand [off-list ref], Heetae Ahn
 [off-list ref], Yuanhan Liu [off-list ref], Jianfeng
 Tan [off-list ref], Neil Horman [off-list ref], Yulong
 Pei [off-list ref]
Subject: Re: [PATCH v5 0/2] Balanced allocation of hugepages

21/06/2017 10:41, Jerin Jacob:

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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.