[dpdk-dev] [PATCH 1/2] eal/ppc: fix mmap for memory initialization

[Sergio Gonzalez Monroy]

Hi Chao,

You mentioned that 'mmap will not respect the requested address hint', 
how does the proposed change solves that?

Is it that hugepages map to a specific VA region, and without 
MAP_HUGETLB you may get address from wrong region?

If mmap were to respect the hinted address, we could do this change 
multi-arch without having to set overcommit hugepages?

fd = -1
addr = mmap(addr, (*size) + hugepage_sz, PROT_READ, MAP_PRIVATE | 
MAP_ANONYMOUS | MAP_HUGETLB, fd, 0)
# Free hugepages mapping
addr = mmap(addr, (*size) + hugepage_sz, PROT_READ, MAP_PRIVATE | 
MAP_ANONYMOUS, fd, 0)

What do you think?

Regards,
Sergio

On 06/04/2017 11:06, Chao Zhu wrote:
> On IBM POWER platform, when mapping /dev/zero file to hugepage memory
> space, mmap will not respect the requested address hint. This will cause
> the memory initilization for the second process fails. This patch adds
> the required mmap flags to make it work. Beside this, users need to set
> the nr_overcommit_hugepages to expand the VA range. When
> doing the initilization, users need to set both nr_hugepages and
> nr_overcommit_hugepages to the same value, like 64, 128, etc.
>
> Signed-off-by: Chao Zhu <chaozhu at linux.vnet.ibm.com>
> ---
>   lib/librte_eal/linuxapp/eal/eal_memory.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
>
> diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c b/lib/librte_eal/linuxapp/eal/eal_memory.c
> index a956bb2..e06186b 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_memory.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
> @@ -313,7 +313,11 @@ int rte_xen_dom0_supported(void)
>   	}
>   	do {
>   		addr = mmap(addr,
> +#ifndef RTE_ARCH_PPC_64
>   				(*size) + hugepage_sz, PROT_READ, MAP_PRIVATE, fd, 0);
> +#else
> +                (*size) + hugepage_sz, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, fd, 0);
> +#endif
>   		if (addr == MAP_FAILED)
>   			*size -= hugepage_sz;
>   	} while (addr == MAP_FAILED && *size > 0);
> @@ -1330,7 +1334,11 @@ static int huge_wrap_sigsetjmp(void)
>   		 * use mmap to get identical addresses as the primary process.
>   		 */
>   		base_addr = mmap(mcfg->memseg[s].addr, mcfg->memseg[s].len,
> +#ifndef RTE_ARCH_PPC_64
>   				 PROT_READ, MAP_PRIVATE, fd_zero, 0);
> +#else
> +                 PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, fd_zero, 0);
> +#endif
>   		if (base_addr == MAP_FAILED ||
>   		    base_addr != mcfg->memseg[s].addr) {
>   			max_seg = s;