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From: Nick Connolly <nick.connolly@mayadata.io>
To: "Burakov, Anatoly" <anatoly.burakov@intel.com>
Cc: dev@dpdk.org, nicolas.dichtel@6wind.com, stable@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] mem: fix allocation failure on non-NUMA kernel
Date: Thu, 17 Sep 2020 14:05:44 +0100	[thread overview]
Message-ID: <eba65564-e165-ddb0-e260-c8dbff4e675e@mayadata.io> (raw)
In-Reply-To: <a77d79ce-5f62-31f4-478e-a252d811f93f@intel.com>

Hi Anatoly,

Thanks.  My recollection is that all of the NUMA configuration flags 
were set to 'n'.


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 :)

  reply	other threads:[~2020-09-17 13:05 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 [this message]
2020-09-17 14:07         ` Burakov, Anatoly
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-dev] [PATCH v2] " Nick Connolly
2020-10-13  7:59   ` Nicolas Dichtel
2020-10-13 12:01     ` David Marchand

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