[PATCH v3 06/13] crypto: iaa - Change cpu-to-iaa mappings to evenly balance cores to IAAs.

Kanchana P Sridhar
2024-11-06T19:21:12Z

This change distributes the cpus more evenly among the IAAs in each socket.

Old algorithm to assign cpus to IAA:
------------------------------------
If "nr_cpus" = nr_logical_cpus (includes hyper-threading), the current
algorithm determines "nr_cpus_per_node" = nr_cpus / nr_nodes.

Hence, on a 2-socket Sapphire Rapids server where each socket has 56 cores
and 4 IAA devices, nr_cpus_per_node = 112.

Further, cpus_per_iaa = (nr_nodes * nr_cpus_per_node) / nr_iaa
Hence, cpus_per_iaa = 224/8 = 28.

The iaa_crypto driver then assigns 28 "logical" node cpus per IAA device
on that node, that results in this cpu-to-iaa mapping:

lscpu|grep NUMA
NUMA node(s): 2
NUMA node0 CPU(s): 0-55,112-167
NUMA node1 CPU(s): 56-111,168-223

NUMA node 0:
cpu 0-27 28-55 112-139 140-167
iaa iax1 iax3 iax5 iax7

NUMA node 1:
cpu 56-83 84-111 168-195 196-223
iaa iax9 iax11 iax13 iax15

This appears non-optimal for a few reasons:

1) The 2 logical threads on a core will get assigned to different IAA
devices. For e.g.:
cpu 0: iax1
cpu 112: iax5
2) One of the logical threads on a core is assigned to an IAA that is not
closest to that core. For e.g. cpu 112.
3) If numactl is used to start processes sequentially on the logical
cores, some of the IAA devices on the socket could be over-subscribed,
while some could be under-utilized.

This patch introduces a scheme to more evenly balance the logical cores to
IAA devices on a socket.

New algorithm to assign cpus to IAA:
------------------------------------
We introduce a function "cpu_to_iaa()" that takes a logical cpu and
returns the IAA device closest to it.

If "nr_cpus" = nr_logical_cpus (includes hyper-threading), the new
algorithm determines "nr_cpus_per_node" = topology_num_cores_per_package().

Hence, on a 2-socket Sapphire Rapids server where each socket has 56 cores
and 4 IAA devices, nr_cpus_per_node = 56.

Further, cpus_per_iaa = (nr_nodes * nr_cpus_per_node) / nr_iaa
Hence, cpus_per_iaa = 112/8 = 14.

The iaa_crypto driver then assigns 14 "logical" node cpus per IAA device
on that node, that results in this cpu-to-iaa mapping:

NUMA node 0:
cpu 0-13,112-125 14-27,126-139 28-41,140-153 42-55,154-167
iaa iax1 iax3 iax5 iax7

NUMA node 1:
cpu 56-69,168-181 70-83,182-195 84-97,196-209 98-111,210-223
iaa iax9 iax11 iax13 iax15

This resolves the 3 issues with non-optimality of cpu-to-iaa mappings
pointed out earlier with the existing approach.

Originally-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
---
drivers/crypto/intel/iaa/iaa_crypto_main.c | 84 ++++++++++++++--------
1 file changed, 54 insertions(+), 30 deletions(-)

diff --git a/drivers/crypto/intel/iaa/iaa_crypto_main.c b/drivers/crypto/intel/iaa/iaa_crypto_main.c
index c4b143dd1ddd..a12a8f9caa84 100644
--- a/drivers/crypto/intel/iaa/iaa_crypto_main.c
+++ b/drivers/crypto/intel/iaa/iaa_crypto_main.c
@@ -55,6 +55,46 @@ static struct idxd_wq *wq_table_next_wq(int cpu)
return entry->wqs[entry->cur_wq];
}

+/*
+ * Given a cpu, find the closest IAA instance. The idea is to try to
+ * choose the most appropriate IAA instance for a caller and spread
+ * available workqueues around to clients.
+ */
+static inline int cpu_to_iaa(int cpu)
+{
+ int node, n_cpus = 0, test_cpu, iaa = 0;
+ int nr_iaa_per_node;
+ const struct cpumask *node_cpus;
+
+ if (!nr_nodes)
+ return 0;
+
+ nr_iaa_per_node = nr_iaa / nr_nodes;
+ if (!nr_iaa_per_node)
+ return 0;
+
+ for_each_online_node(node) {
+ node_cpus = cpumask_of_node(node);
+ if (!cpumask_test_cpu(cpu, node_cpus))
+ continue;
+
+ for_each_cpu(test_cpu, node_cpus) {
+ if ((n_cpus % nr_cpus_per_node) == 0)
+ iaa = node * nr_iaa_per_node;
+
+ if (test_cpu == cpu)
+ return iaa;
+
+ n_cpus++;
+
+ if ((n_cpus % cpus_per_iaa) == 0)
+ iaa++;
+ }
+ }
+
+ return -1;
+}
+
static void wq_table_add(int cpu, struct idxd_wq *wq)
{
struct wq_table_entry *entry = per_cpu_ptr(wq_table, cpu);
@@ -895,8 +935,7 @@ static int wq_table_add_wqs(int iaa, int cpu)
*/
static void rebalance_wq_table(void)
{
- const struct cpumask *node_cpus;
- int node, cpu, iaa = -1;
+ int cpu, iaa;

if (nr_iaa == 0)
return;
@@ -906,37 +945,22 @@ static void rebalance_wq_table(void)

clear_wq_table();

- if (nr_iaa == 1) {
- for (cpu = 0; cpu < nr_cpus; cpu++) {
- if (WARN_ON(wq_table_add_wqs(0, cpu))) {
- pr_debug("could not add any wqs for iaa 0 to cpu %d!\n", cpu);
- return;
- }
- }
-
- return;
- }
-
- for_each_node_with_cpus(node) {
- node_cpus = cpumask_of_node(node);
-
- for (cpu = 0; cpu < cpumask_weight(node_cpus); cpu++) {
- int node_cpu = cpumask_nth(cpu, node_cpus);
-
- if (WARN_ON(node_cpu >= nr_cpu_ids)) {
- pr_debug("node_cpu %d doesn't exist!\n", node_cpu);
- return;
- }
+ for (cpu = 0; cpu < nr_cpus; cpu++) {
+ iaa = cpu_to_iaa(cpu);
+ pr_debug("rebalance: cpu=%d iaa=%d\n", cpu, iaa);

- if ((cpu % cpus_per_iaa) == 0)
- iaa++;
+ if (WARN_ON(iaa == -1)) {
+ pr_debug("rebalance (cpu_to_iaa(%d)) failed!\n", cpu);
+ return;
+ }

- if (WARN_ON(wq_table_add_wqs(iaa, node_cpu))) {
- pr_debug("could not add any wqs for iaa %d to cpu %d!\n", iaa, cpu);
- return;
- }
+ if (WARN_ON(wq_table_add_wqs(iaa, cpu))) {
+ pr_debug("could not add any wqs for iaa %d to cpu %d!\n", iaa, cpu);
+ return;
}
}
+
+ pr_debug("Finished rebalance local wqs.");
}

static inline int check_completion(struct device *dev,
@@ -2332,7 +2356,7 @@ static int __init iaa_crypto_init_module(void)
pr_err("IAA couldn't find any nodes with cpus\n");
return -ENODEV;
}
- nr_cpus_per_node = nr_cpus / nr_nodes;
+ nr_cpus_per_node = topology_num_cores_per_package();

if (crypto_has_comp("deflate-generic", 0, 0))
deflate_generic_tfm = crypto_alloc_comp("deflate-generic", 0, 0);
--
2.27.0