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Date: Tue, 10 May 2022 19:21:41 +0200
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Qing Wang <wangqing@...o.com>, Sudeep Holla <sudeep.holla@....com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arch_topology: support parsing cluster_id from DT
On 05/05/2022 10:35, Qing Wang wrote:
> From: Wang Qing <wangqing@...o.com>
>
> Use nested cluster structures in DT to support describing multi-level
> cluster topologies.
>
> Notice: the clusters describing in DT currently are not physical
> boundaries, since changing "cluster" to "socket" is too involved and error
> prone, this patch will not have any effect on one-level cluster topo, but
> can support the mutil-level cluster topo to support CLUSTER_SCHED.
>
> Signed-off-by: Wang Qing <wangqing@...o.com>
> ---
> drivers/base/arch_topology.c | 25 +++++++++++++++++--------
> 1 file changed, 17 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 1d6636ebaac5..f2ea8113d619 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -491,7 +491,7 @@ static int __init get_cpu_for_node(struct device_node *node)
> }
>
> static int __init parse_core(struct device_node *core, int package_id,
> - int core_id)
> + int cluster_id, int core_id)
> {
> char name[20];
> bool leaf = true;
> @@ -507,6 +507,7 @@ static int __init parse_core(struct device_node *core, int package_id,
> cpu = get_cpu_for_node(t);
> if (cpu >= 0) {
> cpu_topology[cpu].package_id = package_id;
> + cpu_topology[cpu].cluster_id = cluster_id;
> cpu_topology[cpu].core_id = core_id;
> cpu_topology[cpu].thread_id = i;
> } else if (cpu != -ENODEV) {
> @@ -528,6 +529,7 @@ static int __init parse_core(struct device_node *core, int package_id,
> }
>
> cpu_topology[cpu].package_id = package_id;
> + cpu_topology[cpu].cluster_id = cluster_id;
> cpu_topology[cpu].core_id = core_id;
> } else if (leaf && cpu != -ENODEV) {
> pr_err("%pOF: Can't get CPU for leaf core\n", core);
> @@ -544,13 +546,15 @@ static int __init parse_cluster(struct device_node *cluster, int depth)
> bool has_cores = false;
> struct device_node *c;
> static int package_id __initdata;
> + static int cluster_id __initdata;
Starting with cluster_id = 0 breaks existing platforms like
./arch/arm64/boot/dts/arm/juno.dts. For them it has to be still set to -1.
You get e.g.:
# cat /sys/kernel/debug/sched/domains/cpu1/domain*/name
CLS
DIE
instead of:
# cat /sys/kernel/debug/sched/domains/cpu1/domain*/name
MC
DIE
> int core_id = 0;
> int i, ret;
>
> /*
> - * First check for child clusters; we currently ignore any
> - * information about the nesting of clusters and present the
> - * scheduler with a flat list of them.
> + * nesting of clusters :
> + * level 1: package_id
> + * level 2: cluster_id
> + * level 3+: ignore
> */
> i = 0;
> do {
> @@ -559,6 +563,14 @@ static int __init parse_cluster(struct device_node *cluster, int depth)
> if (c) {
> leaf = false;
> ret = parse_cluster(c, depth + 1);
> + if (depth == 0) {
> + package_id++;
> + cluster_id = 0;
- cluster_id = 0;
+ cluster_id = -1;
Would have to be cluster_id = -1. 0 is a valid 2. level cluster.
Otherwise you're not removing the CLS data from CPU4 to CPU7 in the
`Armv9 with L2 complexes` cpu-map example I used for testing:
cpu-map {
cluster0 {
cluster0 {
core0 {
cpu = <&cpu0>;
};
core1 {
cpu = <&cpu1>;
};
};
cluster1 {
core0 {
cpu = <&cpu2>;
};
core1 {
cpu = <&cpu3>;
};
};
};
cluster1 {
core0 {
cpu = <&cpu4>;
};
core1 {
cpu = <&cpu5>;
};
core2 {
cpu = <&cpu6>;
};
};
cluster2 {
core0 {
cpu = <&cpu7>;
};
};
};
> + } else if (depth == 1)
> + cluster_id++;
> + else
> + pr_err("Ignore nested clusters with more than two levels!\n");
> +
> of_node_put(c);
> if (ret != 0)
> return ret;
> @@ -582,7 +594,7 @@ static int __init parse_cluster(struct device_node *cluster, int depth)
> }
>
> if (leaf) {
> - ret = parse_core(c, package_id, core_id++);
> + ret = parse_core(c, package_id, cluster_id, core_id++);
> } else {
> pr_err("%pOF: Non-leaf cluster with core %s\n",
> cluster, name);
> @@ -599,9 +611,6 @@ static int __init parse_cluster(struct device_node *cluster, int depth)
> if (leaf && !has_cores)
> pr_warn("%pOF: empty cluster\n", cluster);
>
> - if (leaf)
> - package_id++;
> -
> return 0;
> }
Looks like you also need to adapt update_siblings_masks() to only set
cpu in &cpu_topo->thread_sibling and &cpuid_topo->thread_sibling when
`cpu_topo->thread_id != -1`.
@@ -723,11 +723,11 @@ void update_siblings_masks(unsigned int cpuid)
cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
cpumask_set_cpu(cpu, &cpuid_topo->core_sibling);
- if (cpuid_topo->core_id != cpu_topo->core_id)
- continue;
-
- cpumask_set_cpu(cpuid, &cpu_topo->thread_sibling);
- cpumask_set_cpu(cpu, &cpuid_topo->thread_sibling);
+ if (cpu_topo->thread_id != -1 &&
+ cpuid_topo->core_id == cpu_topo->core_id) {
+ cpumask_set_cpu(cpuid, &cpu_topo->thread_sibling);
+ cpumask_set_cpu(cpu, &cpuid_topo->thread_sibling);
+
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