Re: [PATCH 2/2] crypto: qat - Enforce valid numa configuration.

[Tadeusz Struk <tadeusz.struk@intel.com>]

On 10/09/2014 10:32 AM, Prarit Bhargava wrote:
>> This calculation is sole for multi-socket configuration. This is why is
>> > was introduced and what it was tested for.
>> > There is no point discussing NUMA for single-socket configuration.
>> > Single socket configurations are not NUMA. In this case dev->numa_node
>> > is usually equal to NUMA_NO_NODE (-1) and adf_get_dev_node_id(pdev) will
>> > always return 0;
> The fact that you return an incorrect value here for any configuration is simply
> put, bad.  You shouldn't do that.

Well I wouldn't say it is incorrect. adf_get_dev_node_id() returns the
phys proc id the dev is connected to, so in single socket configuration
there is only one socket 0.

> 
>> > Please confirm that, but I think the system it panicked on was a two
>> > sockets system with only node 0 populated with memory and accelerator
>> > plugged it to node 1 (phys_proc_id == 1).
>> > In this case adf_get_dev_node_id(pdev) returned 1 and this was passed to
>> > kzalloc_node(size, GFP_KERNEL, 1) and because there was no memory on
>> > node 1 kzalloc_node() panicked.
> Yep; but my interpretation was that node 1 didn't exist at all and it panicked.

Why didn't exist? The fact that there was no memory on node 1 doesn't
make it disappear. There are two sockets in the platform 0 & 1 even
though only one (node 0) has memory. The only problem with that is - it
is far from optimal if device connected to node 1 uses memory on node 0.
And this is what would happen if we would use dev_to_node(dev) here.

> 
>> > This patch will make sure that this will not happen and that the
>> > configuration will be optimal.
>> > 
> Yep, it will.  But what about cpu hotplug?

I don't think cpu hotplug matters here. This is one (probe) time
determination if the configuration is optimal or not and if it makes
sense to use this accelerator or not.