linux-kernel - Re: [PATCH 0/2] arm64/drivers: avoid alloc memory on offline node

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Date:   Thu, 31 May 2018 22:00:51 +0800
From:   Hanjun Guo <guohanjun@...wei.com>
To:     Xie XiuQi <xiexiuqi@...wei.com>, <catalin.marinas@....com>,
        <will.deacon@....com>, <bhelgaas@...gle.com>,
        <gregkh@...uxfoundation.org>, <rafael.j.wysocki@...el.com>,
        <jarkko.sakkinen@...ux.intel.com>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <wanghuiqiang@...wei.com>,
        <tnowicki@...iumnetworks.com>
Subject: Re: [PATCH 0/2] arm64/drivers: avoid alloc memory on offline node

Hi Xiuqi,

On 2018/5/31 20:14, Xie XiuQi wrote:
> A numa system may return node which is not online.
> For example, a numa node:
> 1) without memory
> 2) NR_CPUS is very small, and the cpus on the node are not brought up

I think adding detail info will be easy to be understood:
 - NUMA node will be built if CPUs and (or) memory are valid on this NUMA node;

 - But if we boot the system with memory-less node and also with CONFIG_NR_CPUS
   less than CPUs in SRAT, for example, 64 CPUs total with 4 NUMA nodes, 16 CPUs
   on each NUMA node, if we boot with CONFIG_NR_CPUS=48, then we will not built
   numa node for node 3, but with devices on that numa node, alloc memory will
   be panic because NUMA node 3 is not a valid node.

> 
> In this situation, we use NUMA_NO_NODE to avoid oops.
[snip]
> 
> Xie XiuQi (2):
>   arm64: avoid alloc memory on offline node
>   drivers: check numa node's online status in dev_to_node

I think we still missing devices like SMMU, ITS, so how about check
the numa node online in the core memory allocation such as kmalloc_node()?

Thanks
Hanjun