[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [XEN RFC PATCH 13/40] xen/arm: introduce numa_set_node for Arm
On 25/08/2021 13:07, Wei Chen wrote: Hi Julien, Hi Wei, -----Original Message----- From: Julien Grall <julien@xxxxxxx> Sent: 2021年8月25日 18:37 To: Wei Chen <Wei.Chen@xxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx; sstabellini@xxxxxxxxxx; jbeulich@xxxxxxxx Cc: Bertrand Marquis <Bertrand.Marquis@xxxxxxx> Subject: Re: [XEN RFC PATCH 13/40] xen/arm: introduce numa_set_node for Arm Hi Wei, On 11/08/2021 11:23, Wei Chen wrote:This API is used to set one CPU to a NUMA node. If the system configure NUMA off or system initialize NUMA failed, the online NUMA node would set to only node#0. This will be done in following patches. When NUMA turn off or init failed, node_online_map will be cleared and set node#0 online. So we use node_online_map to prevent to set a CPU to an offline node.IHMO numa_set_node() should behave exactly the same way on x86 and Arm because this is going to be used by the common code. From the commit message, I don't quite understand why the check is necessary on Arm but not on x86. Can you clarify it?Yes, in patch#27, in smpboot.c, dt_smp_init_cpus function. We will parse CPU numa-node-id from dtb CPU node. If we get a valid node ID for one CPU, we will invoke numa_set_node to create CPU-NODE map. But in our testing, we found when NUMA init failed, numa_set_node still can set CPU to a offline or invalid NODE. So we're using node_online_map to prevent this behavior. Otherwise we have to check node_online_map everywhere before we call numa_set_node. What do you mean by invalid NODE? Is it 0xFF (NUMA_NO_NODE)? x86 actually is doing the same way, but it handles node_online_map check out of numa_set_node: Right... I think numa_set_node() will want to be implemented in common code.See my above comment. If x86 is ok, I think yes, we can do it in common code. ... on x86, this check is performed outside of numa_set_node() for one caller whereas on Arm you are adding it in numa_set_node(). For example, numa_set_node() can be called with NUMA_NO_NODE. On x86, we would set cpu_to_node[] to that value. However, if I am not mistaken, on Arm we would set the value to 0. This will change the behavior of users to cpu_to_node() later on (such as XEN_SYSCTL_cputopoinfo). NUMA is not something architecture specific, so I dont't think the implementation should differ here. In this case, I think numa_set_node() shouldn't check if the node is valid. Instead, the caller should take care of it if it is important. Cheers, -- Julien Grall
|
![]() |
Lists.xenproject.org is hosted with RackSpace, monitoring our |