linux-kernel - [PATCH] acpi/hmat,mm/memtier: always register hmat adist calculation callback

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Message-ID: <20240726215548.10653-1-gourry@gourry.net>
Date: Fri, 26 Jul 2024 17:55:48 -0400
From: Gregory Price <gourry@...rry.net>
To: linux-mm@...ck.org
Cc: akpm@...ux-foundation.org,
	ying.huang@...el.com,
	dave.jiang@...el.com,
	Jonathan.Cameron@...wei.com,
	horenchuang@...edance.com,
	linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	dan.j.williams@...el.com,
	lenb@...nel.org
Subject: [PATCH] acpi/hmat,mm/memtier: always register hmat adist calculation callback

In the event that hmat data is not available for the DRAM tier,
or if it is invalid (bandwidth or latency is 0), we can still register
a callback to calculate the abstract distance for non-cpu nodes
and simply assign it a different tier manually.

In the case where DRAM HMAT values are missing or not sane we
manually assign adist=(MEMTIER_ADISTANCE_DRAM + MEMTIER_CHUNK_SIZE).

If the HMAT data for the non-cpu tier is invalid (e.g. bw = 0), we
cannot reasonable determine where to place the tier, so it will default
to MEMTIER_ADISTANCE_DRAM (which is the existing behavior).

Signed-off-by: Gregory Price <gourry@...rry.net>
---
 drivers/acpi/numa/hmat.c |  6 ++++--
 mm/memory-tiers.c        | 10 ++++++++--
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
index 2c8ccc91ebe6..1642d2bd83b5 100644
--- a/drivers/acpi/numa/hmat.c
+++ b/drivers/acpi/numa/hmat.c
@@ -1080,8 +1080,10 @@ static __init int hmat_init(void)
 	if (hotplug_memory_notifier(hmat_callback, HMAT_CALLBACK_PRI))
 		goto out_put;
 
-	if (!hmat_set_default_dram_perf())
-		register_mt_adistance_algorithm(&hmat_adist_nb);
+	if (hmat_set_default_dram_perf())
+		pr_notice("Failed to set default dram perf\n");
+
+	register_mt_adistance_algorithm(&hmat_adist_nb);
 
 	return 0;
 out_put:
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 6632102bd5c9..43bd508938ae 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -765,8 +765,14 @@ int mt_perf_to_adistance(struct access_coordinate *perf, int *adist)
 	    perf->read_bandwidth + perf->write_bandwidth == 0)
 		return -EINVAL;
 
-	if (default_dram_perf_ref_nid == NUMA_NO_NODE)
-		return -ENOENT;
+	/*
+	 * If the DRAM tier did not have valid HMAT data, we can instead just
+	 * assume that the non-cpu numa nodes are 1 tier below cpu nodes
+	 */
+	if (default_dram_perf_ref_nid == NUMA_NO_NODE) {
+		*adist = MEMTIER_ADISTANCE_DRAM + MEMTIER_CHUNK_SIZE;
+		return 0;
+	}
 
 	/*
 	 * The abstract distance of a memory node is in direct proportion to
-- 
2.43.0