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From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>, linuxppc-dev@lists.ozlabs.org
Subject: Re: [RFC PATCH 1/2] powerpc/numa: Introduce logical numa id
Date: Mon, 10 Aug 2020 13:35:37 +0530
Message-ID: <20200810080537.GA10992@linux.vnet.ibm.com> (raw)
In-Reply-To: <87bljoqcje.fsf@linux.ibm.com>

* Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> [2020-08-06 16:14:21]:

> >
> > associativity_to_nid gets called the first time a cpu is being made present
> > from offline. So it need not be in boot path. We may to verify if cpu
> > hotplug, dlpar, operations are synchronized. For example a memory hotadd and
> > cpu hotplug are they synchronized? I am not sure if they are synchronized at
> > this time.
> 
> But you don't online cpu or memory to a non existent node post boot
> right?. If the node is existent we have already initialized the nid_map.
> 

Not sure what you mean by existent and non-existent. Are you referring to
online / offline?

> However i am not sure whether we do a parallel initialization of devices. ie,
> of_device_add getting called in parallel. if it can then we need the
> below?
> 
> @@ -226,6 +226,7 @@ static u32 nid_map[MAX_NUMNODES] = {[0 ... MAX_NUMNODES - 1] =  NUMA_NO_NODE};
>  int firmware_group_id_to_nid(int firmware_gid)
>  {
>         static int last_nid = 0;
> +       static DEFINE_SPINLOCK(node_id_lock);
> 
>         /*
>          * For PowerNV we don't change the node id. This helps to avoid
> @@ -238,8 +239,13 @@ int firmware_group_id_to_nid(int firmware_gid)
>         if (firmware_gid ==  -1)
>                 return NUMA_NO_NODE;
> 
> -       if (nid_map[firmware_gid] == NUMA_NO_NODE)
> -               nid_map[firmware_gid] = last_nid++;
> +       if (nid_map[firmware_gid] == NUMA_NO_NODE) {
> +               spin_lock(&node_id_lock);
> +               /*  recheck with lock held */
> +               if (nid_map[firmware_gid] == NUMA_NO_NODE)
> +                       nid_map[firmware_gid] = last_nid++;
> +               spin_unlock(&node_id_lock);
> +       }
> 
>         return nid_map[firmware_gid];
>  }
> 

This should help.


> 
> I will also add a las_nid > MAX_NUMNODES check in
> firmware_group_id_to_nid() to handle the case where we find more numa
> nodes than MAX_NUMANODES in device tree.
> 

Okay, 

Whats your plan to handle the node distances?
Currently the node distances we compute from the device tree properties are
based on distance from node 0.  If you rename a different node as node 0,
how do you plan to remap the node distances?

> -aneesh

-- 
Thanks and Regards
Srikar Dronamraju

  reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-31 11:19 Aneesh Kumar K.V
2020-07-31 11:22 ` [RFC PATCH 2/2] powerpc/powernv/cpufreq: Don't assume chip id is same as Linux node id Aneesh Kumar K.V
2020-08-04  7:47   ` Gautham R Shenoy
2020-08-01  5:20 ` [RFC PATCH 1/2] powerpc/numa: Introduce logical numa id Srikar Dronamraju
2020-08-02 14:21   ` Aneesh Kumar K.V
2020-08-04  7:25     ` Srikar Dronamraju
2020-08-06 10:44       ` Aneesh Kumar K.V
2020-08-10  8:05         ` Srikar Dronamraju [this message]
2020-08-07  4:24 ` Nathan Lynch
2020-08-07  5:02   ` Aneesh Kumar K.V
2020-08-07 20:45     ` Nathan Lynch
2020-08-09 14:12       ` Aneesh Kumar K.V
2020-08-09 18:40         ` Aneesh Kumar K.V
2020-08-13 22:53           ` Nathan Lynch

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