Re: [PATCH] mem: balanced allocation of hugepages

[Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>]

Hi Ilya,

I have done similar tests and as you already pointed out, 'numactl 
--interleave' does not seem to work as expected.
I have also checked that the issue can be reproduced with quota limit on 
hugetlbfs mount point.

I would be inclined towards *adding libnuma as dependency* to DPDK to 
make memory allocation a bit more reliable.

Currently at a high level regarding hugepages per numa node:
1) Try to map all free hugepages. The total number of mapped hugepages 
depends if there were any limits, such as cgroups or quota in mount point.
2) Find out numa node of each hugepage.
3) Check if we have enough hugepages for requested memory in each numa 
socket/node.

Using libnuma we could try to allocate hugepages per numa:
1) Try to map as many hugepages from numa 0.
2) Check if we have enough hugepages for requested memory in numa 0.
3) Try to map as many hugepages from numa 1.
4) Check if we have enough hugepages for requested memory in numa 1.

This approach would improve failing scenarios caused by limits but It 
would still not fix issues regarding non-contiguous hugepages (worst 
case each hugepage is a memseg).
The non-contiguous hugepages issues are not as critical now that 
mempools can span over multiple memsegs/hugepages, but it is still a 
problem for any other library requiring big chunks of memory.

Potentially if we were to add an option such as 'iommu-only' when all 
devices are bound to vfio-pci, we could have a reliable way to allocate 
hugepages by just requesting the number of pages from each numa.

Thoughts?

Sergio

On 06/03/2017 09:34, Ilya Maximets wrote:
> Hi all.
>
> So, what about this change?
>
> Best regards, Ilya Maximets.
>
> On 16.02.2017 16:01, Ilya Maximets wrote:
>> Currently EAL allocates hugepages one by one not paying
>> attention from which NUMA node allocation was done.
>>
>> Such behaviour leads to allocation failure if number of
>> available hugepages for application limited by cgroups
>> or hugetlbfs and memory requested not only from the first
>> socket.
>>
>> Example:
>> 	# 90 x 1GB hugepages availavle in a system
>>
>> 	cgcreate -g hugetlb:/test
>> 	# Limit to 32GB of hugepages
>> 	cgset -r hugetlb.1GB.limit_in_bytes=34359738368 test
>> 	# Request 4GB from each of 2 sockets
>> 	cgexec -g hugetlb:test testpmd --socket-mem=4096,4096 ...
>>
>> 	EAL: SIGBUS: Cannot mmap more hugepages of size 1024 MB
>> 	EAL: 32 not 90 hugepages of size 1024 MB allocated
>> 	EAL: Not enough memory available on socket 1!
>> 	     Requested: 4096MB, available: 0MB
>> 	PANIC in rte_eal_init():
>> 	Cannot init memory
>>
>> 	This happens beacause all allocated pages are
>> 	on socket 0.
>>
>> Fix this issue by setting mempolicy MPOL_PREFERRED for each
>> hugepage to one of requested nodes in a round-robin fashion.
>> In this case all allocated pages will be fairly distributed
>> between all requested nodes.
>>
>> New config option RTE_LIBRTE_EAL_NUMA_AWARE_HUGEPAGES
>> introduced and disabled by default because of external
>> dependency from libnuma.
>>
>> Cc: <stable@dpdk.org>
>> Fixes: 77988fc08dc5 ("mem: fix allocating all free hugepages")
>>
>> Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
>> ---
>>   config/common_base                       |  1 +
>>   lib/librte_eal/Makefile                  |  4 ++
>>   lib/librte_eal/linuxapp/eal/eal_memory.c | 66 ++++++++++++++++++++++++++++++++
>>   mk/rte.app.mk                            |  3 ++
>>   4 files changed, 74 insertions(+)
>>