[dpdk-dev] [PATCH] mem: fix allocation failure on non-NUMA kernel
Nick Connolly
nick.connolly at mayadata.io
Thu Sep 17 14:29:00 CEST 2020
Hi Anatoly,
Thanks for the response. You are asking a good question - here's what I
know:
The issue arose on a single socket system, running WSL2 (full Linux
kernel running as a lightweight VM under Windows).
The default kernel in this environment is built with CONFIG_NUMA=n which
means get_mempolicy() returns an error.
This causes the check to ensure that the allocated memory is associated
with the correct socket to fail.
The change is to skip the allocation check if check_numa() indicates
that NUMA-aware memory is not supported.
Researching the meaning of CONFIG_NUMA, I found
https://cateee.net/lkddb/web-lkddb/NUMA.html which says:
> Enable NUMA (Non-Uniform Memory Access) support.
> The kernel will try to allocate memory used by a CPU on the local
> memory controller of the CPU and add some more NUMA awareness to the
> kernel.
Clearly CONFIG_NUMA enables memory awareness, but there's no indication
in the description whether information about the NUMA physical
architecture is 'hidden', or whether it is still exposed through
/sys/devices/system/node* (which is used by the rte initialisation code
to determine how many sockets there are). Unfortunately, I don't have
ready access to a multi-socket Linux system that I can test this out on,
so I took the conservative approach that it may be possible to have
CONFIG_NUMA disabled, but the kernel still report more than one node,
and coded the change to generate a debug message if this occurs.
Do you know whether CONFIG_NUMA turns off all knowledge about the
hardware architecture? If it does, then I agree that the test for
rte_socket_count() serves no purpose and should be removed.
Many thanks,
Nick
On 17/09/2020 12:31, Burakov, Anatoly wrote:
> On 05-Aug-20 1:26 PM, Nick Connolly wrote:
>> Running dpdk-helloworld on Linux with lib numa present,
>> but no kernel support for NUMA (CONFIG_NUMA=n) causes
>> ret_service_init() to fail with EAL: error allocating
>> rte services array.
>>
>> alloc_seg() calls get_mempolicy to verify that the allocation
>> has happened on the correct socket, but receives ENOSYS from
>> the kernel and fails the allocation.
>>
>> The allocated socket should only be verified if check_numa() is true.
>>
>> Fixes: 2a96c88be83e ("mem: ease init in a docker container")
>> Cc: nicolas.dichtel at 6wind.com
>> Cc: stable at dpdk.org
>> Signed-off-by: Nick Connolly <nick.connolly at mayadata.io>
>> ---
>> lib/librte_eal/linux/eal_memalloc.c | 28 +++++++++++++++++-----------
>> 1 file changed, 17 insertions(+), 11 deletions(-)
>>
>> diff --git a/lib/librte_eal/linux/eal_memalloc.c
>> b/lib/librte_eal/linux/eal_memalloc.c
>> index db60e7997..179757809 100644
>> --- a/lib/librte_eal/linux/eal_memalloc.c
>> +++ b/lib/librte_eal/linux/eal_memalloc.c
>> @@ -610,17 +610,23 @@ alloc_seg(struct rte_memseg *ms, void *addr,
>> int socket_id,
>> }
>> #ifdef RTE_EAL_NUMA_AWARE_HUGEPAGES
>> - ret = get_mempolicy(&cur_socket_id, NULL, 0, addr,
>> - MPOL_F_NODE | MPOL_F_ADDR);
>> - if (ret < 0) {
>> - RTE_LOG(DEBUG, EAL, "%s(): get_mempolicy: %s\n",
>> - __func__, strerror(errno));
>> - goto mapped;
>> - } else if (cur_socket_id != socket_id) {
>> - RTE_LOG(DEBUG, EAL,
>> - "%s(): allocation happened on wrong socket (wanted
>> %d, got %d)\n",
>> - __func__, socket_id, cur_socket_id);
>> - goto mapped;
>> + if (check_numa()) {
>> + ret = get_mempolicy(&cur_socket_id, NULL, 0, addr,
>> + MPOL_F_NODE | MPOL_F_ADDR);
>> + if (ret < 0) {
>> + RTE_LOG(DEBUG, EAL, "%s(): get_mempolicy: %s\n",
>> + __func__, strerror(errno));
>> + goto mapped;
>> + } else if (cur_socket_id != socket_id) {
>> + RTE_LOG(DEBUG, EAL,
>> + "%s(): allocation happened on wrong socket
>> (wanted %d, got %d)\n",
>> + __func__, socket_id, cur_socket_id);
>> + goto mapped;
>> + }
>> + } else {
>> + if (rte_socket_count() > 1)
>> + RTE_LOG(DEBUG, EAL, "%s(): not checking socket for
>> allocation (wanted %d)\n",
>> + __func__, socket_id);
>> }
>
> If there is no kernel support for NUMA, how would we end up with >1
> socket count?
>
>> #else
>> if (rte_socket_count() > 1)
>>
>
>
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