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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 13:57:43 +0100
Message-ID: <a77d79ce-5f62-31f4-478e-a252d811f93f@intel.com> (raw)
In-Reply-To: <8ebfbd1f-9a2b-3421-1d35-a3cf070ce8df@mayadata.io>

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 :)

-- 
Thanks,
Anatoly

  reply	other threads:[~2020-09-17 12:57 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 [this message]
2020-09-17 13:05       ` Nick Connolly
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-stable] [PATCH v2] " Nick Connolly
2020-10-13  7:59   ` Nicolas Dichtel
2020-10-13 12:01     ` David Marchand

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