From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: Nick Connolly <nick.connolly@mayadata.io>
Cc: dev@dpdk.org, nicolas.dichtel@6wind.com, stable@dpdk.org
Subject: Re: [dpdk-stable] [PATCH] mem: fix allocation failure on non-NUMA kernel
Date: Thu, 17 Sep 2020 15:07:12 +0100 [thread overview]
Message-ID: <2ea114be-d606-229c-4fc0-bac06c0ea2fd@intel.com> (raw)
In-Reply-To: <eba65564-e165-ddb0-e260-c8dbff4e675e@mayadata.io>
On 17-Sep-20 2:05 PM, Nick Connolly wrote:
> Hi Anatoly,
>
> Thanks. My recollection is that all of the NUMA configuration flags
> were set to 'n'.
>
> Regards,
> Nick
>
> On 17/09/2020 13:57, Burakov, Anatoly wrote:
>> On 17-Sep-20 1:29 PM, Nick Connolly wrote:
>>> 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.
>>>
>>
>> I have a system with a custom compiled kernel, i can recompile it
>> without this flag and test this. I'll report back with results :)
>>
>
With CONFIG_NUMA set to 'n':
[root@xxx ~]# find /sys -name "node*"
/sys/kernel/software_nodes/node0
[root@xxx ~]#
This is confirmed by running DPDK on that machine - i can see all cores
from all sockets, but they're all appearing on socket 0. So, yes, that
check isn't necessary :)
--
Thanks,
Anatoly
next prev parent reply other threads:[~2020-09-17 14:10 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-05 12:26 Nick Connolly
2020-08-05 13:42 ` Nicolas Dichtel
2020-08-05 14:20 ` Nick Connolly
2020-08-05 14:36 ` Nicolas Dichtel
2020-08-05 14:53 ` Nick Connolly
2020-08-05 15:13 ` Nicolas Dichtel
2020-08-05 15:21 ` Nick Connolly
2020-09-17 11:28 ` Burakov, Anatoly
2020-09-17 11:31 ` Burakov, Anatoly
2020-09-17 12:29 ` Nick Connolly
2020-09-17 12:57 ` Burakov, Anatoly
2020-09-17 13:05 ` Nick Connolly
2020-09-17 14:07 ` Burakov, Anatoly [this message]
2020-09-17 14:08 ` Nick Connolly
2020-09-17 14:18 ` Burakov, Anatoly
2020-09-17 14:19 ` Nick Connolly
2020-10-12 19:28 ` [dpdk-stable] [PATCH v2] " Nick Connolly
2020-10-13 7:59 ` Nicolas Dichtel
2020-10-13 12:01 ` David Marchand
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2ea114be-d606-229c-4fc0-bac06c0ea2fd@intel.com \
--to=anatoly.burakov@intel.com \
--cc=dev@dpdk.org \
--cc=nick.connolly@mayadata.io \
--cc=nicolas.dichtel@6wind.com \
--cc=stable@dpdk.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).