Commit a4bec516 authored by Gautham R. Shenoy's avatar Gautham R. Shenoy Committed by Michael Ellerman
Browse files

powerpc/cacheinfo: Lookup cache by dt node and thread-group id 



Currently the cacheinfo code on powerpc indexes the "cache" objects
(modelling the L1/L2/L3 caches) where the key is device-tree node
corresponding to that cache. On some of the POWER server platforms
thread-groups within the core share different sets of caches (Eg: On
SMT8 POWER9 systems, threads 0,2,4,6 of a core share L1 cache and
threads 1,3,5,7 of the same core share another L1 cache). On such
platforms, there is a single device-tree node corresponding to that
cache and the cache-configuration within the threads of the core is
indicated via "ibm,thread-groups" device-tree property.

Since the current code is not aware of the "ibm,thread-groups"
property, on the aforementoined systems, cacheinfo code still treats
all the threads in the core to be sharing the cache because of the
single device-tree node (In the earlier example, the cacheinfo code
would says CPUs 0-7 share L1 cache).

In this patch, we make the powerpc cacheinfo code aware of the
"ibm,thread-groups" property. We indexe the "cache" objects by the
key-pair (device-tree node, thread-group id). For any CPUX, for a
given level of cache, the thread-group id is defined to be the first
CPU in the "ibm,thread-groups" cache-group containing CPUX. For levels
of cache which are not represented in "ibm,thread-groups" property,
the thread-group id is -1.

[parth: Remove "static" keyword for the definition of "thread_group_l1_cache_map"
and "thread_group_l2_cache_map" to get rid of the compile error.]

Signed-off-by: default avatarGautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: default avatarParth Shah <parth@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210728175607.591679-2-parth@linux.ibm.com
parent 86ff0bce

arch/powerpc/include/asm/smp.h

+3 −0
Original line number Diff line number Diff line
@@ -33,6 +33,9 @@ extern bool coregroup_enabled; 
extern int cpu_to_chip_id(int cpu);

extern int *chip_id_lookup_table;



DECLARE_PER_CPU(cpumask_var_t, thread_group_l1_cache_map);

DECLARE_PER_CPU(cpumask_var_t, thread_group_l2_cache_map);



#ifdef CONFIG_SMP



struct smp_ops_t {

arch/powerpc/kernel/cacheinfo.c

+58 −22
Original line number Diff line number Diff line
@@ -120,6 +120,7 @@ struct cache { 
	struct cpumask shared_cpu_map; /* online CPUs using this cache */

	int type;                      /* split cache disambiguation */

	int level;                     /* level not explicit in device tree */

	int group_id;                  /* id of the group of threads that share this cache */

	struct list_head list;         /* global list of cache objects */

	struct cache *next_local;      /* next cache of >= level */

};
@@ -142,22 +143,24 @@ static const char *cache_type_string(const struct cache *cache) 
}



static void cache_init(struct cache *cache, int type, int level,

		       struct device_node *ofnode)

		       struct device_node *ofnode, int group_id)

{

	cache->type = type;

	cache->level = level;

	cache->ofnode = of_node_get(ofnode);

	cache->group_id = group_id;

	INIT_LIST_HEAD(&cache->list);

	list_add(&cache->list, &cache_list);

}



static struct cache *new_cache(int type, int level, struct device_node *ofnode)

static struct cache *new_cache(int type, int level,

			       struct device_node *ofnode, int group_id)

{

	struct cache *cache;



	cache = kzalloc(sizeof(*cache), GFP_KERNEL);

	if (cache)

		cache_init(cache, type, level, ofnode);

		cache_init(cache, type, level, ofnode, group_id);



	return cache;

}
@@ -309,20 +312,24 @@ static struct cache *cache_find_first_sibling(struct cache *cache) 
		return cache;



	list_for_each_entry(iter, &cache_list, list)

		if (iter->ofnode == cache->ofnode && iter->next_local == cache)

		if (iter->ofnode == cache->ofnode &&

		    iter->group_id == cache->group_id &&

		    iter->next_local == cache)

			return iter;



	return cache;

}



/* return the first cache on a local list matching node */

static struct cache *cache_lookup_by_node(const struct device_node *node)

/* return the first cache on a local list matching node and thread-group id */

static struct cache *cache_lookup_by_node_group(const struct device_node *node,

						int group_id)

{

	struct cache *cache = NULL;

	struct cache *iter;



	list_for_each_entry(iter, &cache_list, list) {

		if (iter->ofnode != node)

		if (iter->ofnode != node ||

		    iter->group_id != group_id)

			continue;

		cache = cache_find_first_sibling(iter);

		break;
@@ -352,14 +359,15 @@ static int cache_is_unified_d(const struct device_node *np) 
		CACHE_TYPE_UNIFIED_D : CACHE_TYPE_UNIFIED;

}



static struct cache *cache_do_one_devnode_unified(struct device_node *node, int level)

static struct cache *cache_do_one_devnode_unified(struct device_node *node, int group_id,

						  int level)

{

	pr_debug("creating L%d ucache for %pOFP\n", level, node);



	return new_cache(cache_is_unified_d(node), level, node);

	return new_cache(cache_is_unified_d(node), level, node, group_id);

}



static struct cache *cache_do_one_devnode_split(struct device_node *node,

static struct cache *cache_do_one_devnode_split(struct device_node *node, int group_id,

						int level)

{

	struct cache *dcache, *icache;
@@ -367,8 +375,8 @@ static struct cache *cache_do_one_devnode_split(struct device_node *node, 
	pr_debug("creating L%d dcache and icache for %pOFP\n", level,

		 node);



	dcache = new_cache(CACHE_TYPE_DATA, level, node);

	icache = new_cache(CACHE_TYPE_INSTRUCTION, level, node);

	dcache = new_cache(CACHE_TYPE_DATA, level, node, group_id);

	icache = new_cache(CACHE_TYPE_INSTRUCTION, level, node, group_id);



	if (!dcache || !icache)

		goto err;
@@ -382,31 +390,32 @@ static struct cache *cache_do_one_devnode_split(struct device_node *node, 
	return NULL;

}



static struct cache *cache_do_one_devnode(struct device_node *node, int level)

static struct cache *cache_do_one_devnode(struct device_node *node, int group_id, int level)

{

	struct cache *cache;



	if (cache_node_is_unified(node))

		cache = cache_do_one_devnode_unified(node, level);

		cache = cache_do_one_devnode_unified(node, group_id, level);

	else

		cache = cache_do_one_devnode_split(node, level);

		cache = cache_do_one_devnode_split(node, group_id, level);



	return cache;

}



static struct cache *cache_lookup_or_instantiate(struct device_node *node,

						 int group_id,

						 int level)

{

	struct cache *cache;



	cache = cache_lookup_by_node(node);

	cache = cache_lookup_by_node_group(node, group_id);



	WARN_ONCE(cache && cache->level != level,

		  "cache level mismatch on lookup (got %d, expected %d)\n",

		  cache->level, level);



	if (!cache)

		cache = cache_do_one_devnode(node, level);

		cache = cache_do_one_devnode(node, group_id, level);



	return cache;

}
@@ -443,7 +452,27 @@ static void do_subsidiary_caches_debugcheck(struct cache *cache) 
		  of_node_get_device_type(cache->ofnode));

}



static void do_subsidiary_caches(struct cache *cache)

/*

 * If sub-groups of threads in a core containing @cpu_id share the

 * L@level-cache (information obtained via "ibm,thread-groups"

 * device-tree property), then we identify the group by the first

 * thread-sibling in the group. We define this to be the group-id.

 *

 * In the absence of any thread-group information for L@level-cache,

 * this function returns -1.

 */

static int get_group_id(unsigned int cpu_id, int level)

{

	if (has_big_cores && level == 1)

		return cpumask_first(per_cpu(thread_group_l1_cache_map,

					     cpu_id));

	else if (thread_group_shares_l2 && level == 2)

		return cpumask_first(per_cpu(thread_group_l2_cache_map,

					     cpu_id));

	return -1;

}



static void do_subsidiary_caches(struct cache *cache, unsigned int cpu_id)

{

	struct device_node *subcache_node;

	int level = cache->level;
@@ -452,9 +481,11 @@ static void do_subsidiary_caches(struct cache *cache) 


	while ((subcache_node = of_find_next_cache_node(cache->ofnode))) {

		struct cache *subcache;

		int group_id;



		level++;

		subcache = cache_lookup_or_instantiate(subcache_node, level);

		group_id = get_group_id(cpu_id, level);

		subcache = cache_lookup_or_instantiate(subcache_node, group_id, level);

		of_node_put(subcache_node);

		if (!subcache)

			break;
@@ -468,6 +499,7 @@ static struct cache *cache_chain_instantiate(unsigned int cpu_id) 
{

	struct device_node *cpu_node;

	struct cache *cpu_cache = NULL;

	int group_id;



	pr_debug("creating cache object(s) for CPU %i\n", cpu_id);
@@ -476,11 +508,13 @@ static struct cache *cache_chain_instantiate(unsigned int cpu_id) 
	if (!cpu_node)

		goto out;



	cpu_cache = cache_lookup_or_instantiate(cpu_node, 1);

	group_id = get_group_id(cpu_id, 1);



	cpu_cache = cache_lookup_or_instantiate(cpu_node, group_id, 1);

	if (!cpu_cache)

		goto out;



	do_subsidiary_caches(cpu_cache);

	do_subsidiary_caches(cpu_cache, cpu_id);



	cache_cpu_set(cpu_cache, cpu_id);

out:
@@ -848,13 +882,15 @@ static struct cache *cache_lookup_by_cpu(unsigned int cpu_id) 
{

	struct device_node *cpu_node;

	struct cache *cache;

	int group_id;



	cpu_node = of_get_cpu_node(cpu_id, NULL);

	WARN_ONCE(!cpu_node, "no OF node found for CPU %i\n", cpu_id);

	if (!cpu_node)

		return NULL;



	cache = cache_lookup_by_node(cpu_node);

	group_id = get_group_id(cpu_id, 1);

	cache = cache_lookup_by_node_group(cpu_node, group_id);

	of_node_put(cpu_node);



	return cache;

arch/powerpc/kernel/smp.c

+2 −2
Original line number Diff line number Diff line
@@ -122,14 +122,14 @@ static struct thread_groups_list tgl[NR_CPUS] __initdata; 
 * On big-cores system, thread_group_l1_cache_map for each CPU corresponds to

 * the set its siblings that share the L1-cache.

 */

static DEFINE_PER_CPU(cpumask_var_t, thread_group_l1_cache_map);

DEFINE_PER_CPU(cpumask_var_t, thread_group_l1_cache_map);



/*

 * On some big-cores system, thread_group_l2_cache_map for each CPU

 * corresponds to the set its siblings within the core that share the

 * L2-cache.

 */

static DEFINE_PER_CPU(cpumask_var_t, thread_group_l2_cache_map);

DEFINE_PER_CPU(cpumask_var_t, thread_group_l2_cache_map);



/* SMP operations for this machine */

struct smp_ops_t *smp_ops;