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Message-Id: <20240628161302.240043-3-xavier_qy@163.com>
Date: Sat, 29 Jun 2024 00:13:02 +0800
From: Xavier <xavier_qy@....com>
To: tj@...nel.org
Cc: longman@...hat.com,
mkoutny@...e.com,
lizefan.x@...edance.com,
hannes@...xchg.org,
cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org,
torvalds@...ux-foundation.org,
akpm@...ux-foundation.org,
Xavier <xavier_qy@....com>
Subject: [PATCH-cpuset v8 2/2] cpuset: use Union-Find to optimize the merging of cpumasks
The process of constructing scheduling domains
involves multiple loops and repeated evaluations, leading to numerous
redundant and ineffective assessments that impact code efficiency.
Here, we use Union-Find to optimize the merging of cpumasks. By employing
path compression and union by rank, we effectively reduce the number of
lookups and merge comparisons.
Signed-off-by: Xavier <xavier_qy@....com>
---
kernel/cgroup/cpuset.c | 96 ++++++++++++++++--------------------------
1 file changed, 37 insertions(+), 59 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index fe76045aa5..c435814ba8 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -45,6 +45,8 @@
#include <linux/cgroup.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
+#include <linux/union_find.h>
+#include <linux/vmalloc.h>
DEFINE_STATIC_KEY_FALSE(cpusets_pre_enable_key);
DEFINE_STATIC_KEY_FALSE(cpusets_enabled_key);
@@ -172,9 +174,6 @@ struct cpuset {
*/
int attach_in_progress;
- /* partition number for rebuild_sched_domains() */
- int pn;
-
/* for custom sched domain */
int relax_domain_level;
@@ -208,6 +207,9 @@ struct cpuset {
/* Remote partition silbling list anchored at remote_children */
struct list_head remote_sibling;
+
+ /* Used to merge intersecting subsets for generate_sched_domains*/
+ struct uf_node node;
};
/*
@@ -1007,7 +1009,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
struct cpuset *cp; /* top-down scan of cpusets */
struct cpuset **csa; /* array of all cpuset ptrs */
int csn; /* how many cpuset ptrs in csa so far */
- int i, j, k; /* indices for partition finding loops */
+ int i, j; /* indices for partition finding loops */
cpumask_var_t *doms; /* resulting partition; i.e. sched domains */
struct sched_domain_attr *dattr; /* attributes for custom domains */
int ndoms = 0; /* number of sched domains in result */
@@ -1015,6 +1017,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
struct cgroup_subsys_state *pos_css;
bool root_load_balance = is_sched_load_balance(&top_cpuset);
bool cgrpv2 = cgroup_subsys_on_dfl(cpuset_cgrp_subsys);
+ int nslot_update;
doms = NULL;
dattr = NULL;
@@ -1102,31 +1105,25 @@ static int generate_sched_domains(cpumask_var_t **domains,
if (root_load_balance && (csn == 1))
goto single_root_domain;
- for (i = 0; i < csn; i++)
- csa[i]->pn = i;
- ndoms = csn;
-
-restart:
- /* Find the best partition (set of sched domains) */
- for (i = 0; i < csn; i++) {
- struct cpuset *a = csa[i];
- int apn = a->pn;
+ if (!cgrpv2) {
+ for (i = 0; i < csn; i++)
+ uf_nodes_init(&csa[i]->node);
- for (j = 0; j < csn; j++) {
- struct cpuset *b = csa[j];
- int bpn = b->pn;
-
- if (apn != bpn && cpusets_overlap(a, b)) {
- for (k = 0; k < csn; k++) {
- struct cpuset *c = csa[k];
-
- if (c->pn == bpn)
- c->pn = apn;
- }
- ndoms--; /* one less element */
- goto restart;
+ /* Merge overlapping cpusets */
+ for (i = 0; i < csn; i++) {
+ for (j = i + 1; j < csn; j++) {
+ if (cpusets_overlap(csa[i], csa[j]))
+ uf_union(&csa[i]->node, &csa[j]->node);
}
}
+
+ /* Count the total number of domains */
+ for (i = 0; i < csn; i++) {
+ if (csa[i]->node.parent == &csa[i]->node)
+ ndoms++;
+ }
+ } else {
+ ndoms = csn;
}
/*
@@ -1159,44 +1156,25 @@ static int generate_sched_domains(cpumask_var_t **domains,
}
for (nslot = 0, i = 0; i < csn; i++) {
- struct cpuset *a = csa[i];
- struct cpumask *dp;
- int apn = a->pn;
-
- if (apn < 0) {
- /* Skip completed partitions */
- continue;
- }
-
- dp = doms[nslot];
-
- if (nslot == ndoms) {
- static int warnings = 10;
- if (warnings) {
- pr_warn("rebuild_sched_domains confused: nslot %d, ndoms %d, csn %d, i %d, apn %d\n",
- nslot, ndoms, csn, i, apn);
- warnings--;
- }
- continue;
- }
-
- cpumask_clear(dp);
- if (dattr)
- *(dattr + nslot) = SD_ATTR_INIT;
+ nslot_update = 0;
for (j = i; j < csn; j++) {
- struct cpuset *b = csa[j];
-
- if (apn == b->pn) {
- cpumask_or(dp, dp, b->effective_cpus);
+ if (uf_find(&csa[j]->node) == &csa[i]->node) {
+ struct cpumask *dp = doms[nslot];
+
+ if (i == j) {
+ nslot_update = 1;
+ cpumask_clear(dp);
+ if (dattr)
+ *(dattr + nslot) = SD_ATTR_INIT;
+ }
+ cpumask_or(dp, dp, csa[j]->effective_cpus);
cpumask_and(dp, dp, housekeeping_cpumask(HK_TYPE_DOMAIN));
if (dattr)
- update_domain_attr_tree(dattr + nslot, b);
-
- /* Done with this partition */
- b->pn = -1;
+ update_domain_attr_tree(dattr + nslot, csa[j]);
}
}
- nslot++;
+ if (nslot_update)
+ nslot++;
}
BUG_ON(nslot != ndoms);
--
2.45.2
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