Re: [PATCH] mem: balanced allocation of hugepages

On 27.03.2017 16:01, Sergio Gonzalez Monroy wrote:

On 09/03/2017 12:57, Ilya Maximets wrote:

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On 08.03.2017 16:46, Sergio Gonzalez Monroy wrote:

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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?

Hi Sergio,

Thanks for your attention to this.

For now, as we have some issues with non-contiguous
hugepages, I'm thinking about following hybrid schema:
1) Allocate essential hugepages:
    1.1) Allocate as many hugepages from numa N to
         only fit requested memory for this numa.
    1.2) repeat 1.1 for all numa nodes.
2) Try to map all remaining free hugepages in a round-robin
    fashion like in this patch.
3) Sort pages and choose the most suitable.

This solution should decrease number of issues connected with
non-contiguous memory.

Sorry for late reply, I was hoping for more comments from the community.

IMHO this should be default behavior, which means no config option and libnuma as EAL dependency.
I think your proposal is good, could you consider implementing such approach on next release?

Sure, I can implement this for 17.08 release.

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On 06/03/2017 09:34, Ilya Maximets wrote:

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Hi all.

So, what about this change?

Best regards, Ilya Maximets.

On 16.02.2017 16:01, Ilya Maximets wrote:

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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:[off-list ref]
Fixes: 77988fc08dc5 ("mem: fix allocating all free hugepages")

Signed-off-by: Ilya Maximets<redacted>
---
   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(+)

Acked-by: Sergio Gonzalez Monroy <redacted>

Thanks.

Best regards, Ilya Maximets.