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From: SeongJae Park <sj@kernel.org>
To: 
Cc: SeongJae Park <sj@kernel.org>,
	linux-kernel@vger.kernel.org,
	damon@lists.linux.dev,
	linux-mm@kvack.org
Subject: [RFC IDEA v2 2/6] mm/damon: add the initial part of access/contiguity-aware memory auto-scaling module
Date: Sun, 12 May 2024 12:36:53 -0700
Message-Id: <20240512193657.79298-3-sj@kernel.org>
In-Reply-To: <20240512193657.79298-1-sj@kernel.org>
References: <20240512193657.79298-1-sj@kernel.org>
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Start adding a DAMON application module for access/contiguity-aware
memory auto-scaling.  The module does proactive reclamation, scale-down,
and scale-up of memory under user-defined min/max memory and acceptable
level of memory pressure using three DAMOS schemes each designed for
each of the three main operations.  Nonetheless, this is only the
initial part of the implementation.  Hence this commit implements only
the memory pressure-aware auto-tuning proactive reclamation feature.
Following commits will implement scale down and up, respectively.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/Kconfig  |  10 ++
 mm/damon/Makefile |   1 +
 mm/damon/acma.c   | 335 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 346 insertions(+)
 create mode 100644 mm/damon/acma.c

diff --git a/mm/damon/Kconfig b/mm/damon/Kconfig
index fecb8172410c..4fe7520601dd 100644
--- a/mm/damon/Kconfig
+++ b/mm/damon/Kconfig
@@ -121,4 +121,14 @@ config DAMON_LRU_SORT
 	  protect frequently accessed (hot) pages while rarely accessed (cold)
 	  pages reclaimed first under memory pressure.
 
+config DAMON_ACMA
+	bool "Build Access/Contiguity-aware Memory Auto-scaling (DAMON_ACMA)"
+	depends on DAMON_PADDR
+	help
+	  This builds the DAMON-based Access/Contiguity-aware Memory
+	  Auto-scaling subsystem.  It preempts unnecessary memory from the
+	  system and report it to the host while respecting user-specified
+	  min/max memory for the system and maximum memory pressure stall time
+	  ratio.
+
 endmenu
diff --git a/mm/damon/Makefile b/mm/damon/Makefile
index f7add3f4aa79..814c8da3081b 100644
--- a/mm/damon/Makefile
+++ b/mm/damon/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_DAMON_SYSFS)	+= sysfs-common.o sysfs-schemes.o sysfs.o
 obj-$(CONFIG_DAMON_DBGFS)	+= dbgfs.o
 obj-$(CONFIG_DAMON_RECLAIM)	+= modules-common.o reclaim.o
 obj-$(CONFIG_DAMON_LRU_SORT)	+= modules-common.o lru_sort.o
+obj-$(CONFIG_DAMON_ACMA)	+= modules-common.o acma.o
diff --git a/mm/damon/acma.c b/mm/damon/acma.c
new file mode 100644
index 000000000000..276b61fd4e26
--- /dev/null
+++ b/mm/damon/acma.c
@@ -0,0 +1,335 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DAMON-based Access/Contiguity-aware Memory Auto-scaling
+ *
+ * Let user specifies min/max memory of the system and acceptable level of
+ * memory pressure stall level.  While respecting those, automatically scale
+ * the memory of the system up and down by scale_downing memory from the system
+ * and report it to the host when the system is having memory pressure level
+ * under the threshold, and vice versa, respectively.
+ *
+ * At this moment, the scaling is not implemented, hence this is just a memory
+ * pressure-aware proactive reclamation module.
+ *
+ * Author: SeongJae Park <sj@kernel.org>
+ */
+
+#define pr_fmt(fmt) "damon-acma: " fmt
+
+#include <linux/damon.h>
+#include <linux/kstrtox.h>
+#include <linux/module.h>
+
+#include "modules-common.h"
+
+#ifdef MODULE_PARAM_PREFIX
+#undef MODULE_PARAM_PREFIX
+#endif
+#define MODULE_PARAM_PREFIX "damon_acma."
+
+/*
+ * Enable or disable DAMON_ACMA.
+ *
+ * You can enable DAMON_ACMA by setting the value of this parameter as ``Y``.
+ * Setting it as ``N`` disables DAMON_ACMA.  Note that DAMON_ACMA could do no
+ * real monitoring and memory auto-scaling due to the watermarks-based
+ * activation condition.  Refer to below descriptions for the watermarks
+ * parameter for this.
+ */
+static bool enabled __read_mostly;
+
+/*
+ * Make DAMON_ACMA reads the input parameters again, except ``enabled``.
+ *
+ * Input parameters that updated while DAMON_ACMA is running are not
+ * applied by default.  Once this parameter is set as ``Y``, DAMON_ACMA
+ * reads values of parametrs except ``enabled`` again.  Once the re-reading is
+ * done, this parameter is set as ``N``.  If invalid parameters are found while
+ * the re-reading, DAMON_ACMA will be disabled.
+ */
+static bool commit_inputs __read_mostly;
+module_param(commit_inputs, bool, 0600);
+
+/*
+ * Desired level of memory pressure-stall time in microseconds.
+ *
+ * While keeping the caps that set by other quotas, DAMON_RECLAIM automatically
+ * increases and decreases the effective level of the quota aiming this level of
+ * memory pressure is incurred.  System-wide ``some`` memory PSI in microseconds
+ * per quota reset interval (``quota_reset_interval_ms``) is collected and
+ * compared to this value to see if the aim is satisfied.  Value zero means
+ * disabling this auto-tuning feature.
+ *
+ * 1 ms/ 1 second (0.1%) by default.  Inspired by the PSI threshold of TMO
+ * (https://dl.acm.org/doi/10.1145/3503222.3507731).
+ */
+static unsigned long quota_mem_pressure_us __read_mostly = 1000;
+module_param(quota_mem_pressure_us, ulong, 0600);
+
+static struct damos_quota damon_acma_quota = {
+	/* Use up to 15 ms per 1 sec for scaling, by default */
+	.ms = 15,
+	.sz = 0,
+	.reset_interval = 1000,
+	/* Within the quota, mark hotter regions accessed first. */
+	.weight_sz = 0,
+	.weight_nr_accesses = 1,
+	.weight_age = 0,
+};
+DEFINE_DAMON_MODULES_DAMOS_TIME_QUOTA(damon_acma_quota);
+
+static struct damos_watermarks damon_acma_wmarks = {
+	.metric = DAMOS_WMARK_NONE,
+};
+
+static struct damon_attrs damon_acma_mon_attrs = {
+	.sample_interval = 1000000,	/* 1 second */
+	.aggr_interval = 20000000,	/* 20 seconds */
+	.ops_update_interval = 0,
+	.min_nr_regions = 10,
+	.max_nr_regions = 1000,
+};
+DEFINE_DAMON_MODULES_MON_ATTRS_PARAMS(damon_acma_mon_attrs);
+
+/*
+ * Start of the target memory region in physical address.
+ *
+ * The start physical address of memory region that DAMON_ACMA will do work
+ * against.  By default, biggest System RAM is used as the region.
+ */
+static unsigned long monitor_region_start __read_mostly;
+module_param(monitor_region_start, ulong, 0600);
+
+/*
+ * End of the target memory region in physical address.
+ *
+ * The end physical address of memory region that DAMON_ACMA will do work
+ * against.  By default, biggest System RAM is used as the region.
+ */
+static unsigned long monitor_region_end __read_mostly;
+module_param(monitor_region_end, ulong, 0600);
+
+/*
+ * PID of the DAMON thread
+ *
+ * If DAMON_ACMA is enabled, this becomes the PID of the worker thread.
+ * Else, -1.
+ */
+static int kdamond_pid __read_mostly = -1;
+module_param(kdamond_pid, int, 0400);
+
+static struct damos_stat damon_acma_reclaim_stat;
+DEFINE_DAMON_MODULES_DAMOS_STATS_PARAMS(damon_acma_reclaim_stat,
+		acma_reclaim_tried_regions, acma_reclaim_succ_regions,
+		acma_reclaim_quota_exceeds);
+
+static struct damos_access_pattern damon_acma_stub_pattern = {
+	/* Find regions having PAGE_SIZE or larger size */
+	.min_sz_region = PAGE_SIZE,
+	.max_sz_region = ULONG_MAX,
+	/* no matter its access frequency */
+	.min_nr_accesses = 0,
+	.max_nr_accesses = UINT_MAX,
+	/* no matter its age */
+	.min_age_region = 0,
+	.max_age_region = UINT_MAX,
+};
+
+static struct damon_ctx *ctx;
+static struct damon_target *target;
+
+static struct damos *damon_acma_new_scheme(
+		struct damos_access_pattern *pattern, enum damos_action action)
+{
+	struct damos_quota quota = damon_acma_quota;
+
+	return damon_new_scheme(
+			pattern,
+			action,
+			/* work for every second */
+			1000000,
+			/* under the quota. */
+			&quota,
+			/* (De)activate this according to the watermarks. */
+			&damon_acma_wmarks);
+}
+
+static void damon_acma_copy_quota_status(struct damos_quota *dst,
+		struct damos_quota *src)
+{
+	dst->total_charged_sz = src->total_charged_sz;
+	dst->total_charged_ns = src->total_charged_ns;
+	dst->charged_sz = src->charged_sz;
+	dst->charged_from = src->charged_from;
+	dst->charge_target_from = src->charge_target_from;
+	dst->charge_addr_from = src->charge_addr_from;
+}
+
+static int damon_acma_set_scheme_quota(struct damos *scheme, struct damos *old,
+		damos_quota_goal_metric goal_metric)
+{
+	if (old)
+		damon_acma_copy_quota_status(&scheme->quota, &old->quota);
+	goal = damos_new_quota_goal(goal_metric, quota_mem_pressure_us);
+	if (!goal)
+		return -ENOMEM;
+	damos_add_quota_goal(&scheme->quota, goal);
+	return 0;
+}
+
+/*
+ * Reclaim cold pages on entire physical address space
+ */
+static struct damos *damon_acma_new_reclaim_scheme(struct damos *old)
+{
+	struct damos_access_pattern pattern = damon_acma_stub_pattern;
+	struct damos *scheme;
+	int err;
+
+	pattern.max_nr_accesses = 0;
+	scheme = damon_acma_new_scheme(&pattern, DAMOS_PAGEOUT);
+	if (!scheme)
+		return NULL;
+	err = damon_acma_set_scheme_quota(scheme, old,
+			DAMOS_QUOTA_SOME_MEM_PSI_US);
+	if (err) {
+		damon_destroy_scheme(scheme);
+		return NULL;
+	}
+	return scheme;
+}
+
+static int damon_acma_apply_parameters(void)
+{
+	struct damos *scheme, *reclaim_scheme;
+	struct damos *old_reclaim_scheme = NULL;
+	struct damos_quota_goal *goal;
+	int err = 0;
+
+	err = damon_set_attrs(ctx, &damon_acma_mon_attrs);
+	if (err)
+		return err;
+
+	damon_for_each_scheme(scheme, ctx)
+		old_reclaim_scheme = scheme;
+
+	reclaim_scheme = damon_acma_new_reclaim_scheme(old_reclaim_scheme);
+	if (!reclaim_scheme)
+		return -ENOMEM;
+	damon_set_schemes(ctx, &reclaim_scheme, 1);
+
+	return damon_set_region_biggest_system_ram_default(target,
+					&monitor_region_start,
+					&monitor_region_end);
+}
+
+static int damon_acma_turn(bool on)
+{
+	int err;
+
+	if (!on) {
+		err = damon_stop(&ctx, 1);
+		if (!err)
+			kdamond_pid = -1;
+		return err;
+	}
+
+	err = damon_acma_apply_parameters();
+	if (err)
+		return err;
+
+	err = damon_start(&ctx, 1, true);
+	if (err)
+		return err;
+	kdamond_pid = ctx->kdamond->pid;
+	return 0;
+}
+
+static int damon_acma_enabled_store(const char *val,
+		const struct kernel_param *kp)
+{
+	bool is_enabled = enabled;
+	bool enable;
+	int err;
+
+	err = kstrtobool(val, &enable);
+	if (err)
+		return err;
+
+	if (is_enabled == enable)
+		return 0;
+
+	/* Called before init function.  The function will handle this. */
+	if (!ctx)
+		goto set_param_out;
+
+	err = damon_acma_turn(enable);
+	if (err)
+		return err;
+
+set_param_out:
+	enabled = enable;
+	return err;
+}
+
+static const struct kernel_param_ops enabled_param_ops = {
+	.set = damon_acma_enabled_store,
+	.get = param_get_bool,
+};
+
+module_param_cb(enabled, &enabled_param_ops, &enabled, 0600);
+MODULE_PARM_DESC(enabled,
+	"Enable or disable DAMON_ACMA (default: disabled)");
+
+static int damon_acma_handle_commit_inputs(void)
+{
+	int err;
+
+	if (!commit_inputs)
+		return 0;
+
+	err = damon_acma_apply_parameters();
+	commit_inputs = false;
+	return err;
+}
+
+static int damon_acma_after_aggregation(struct damon_ctx *c)
+{
+	struct damos *s;
+
+	/* update the stats parameter */
+	damon_for_each_scheme(s, c) {
+		switch (s->action) {
+		case DAMOS_LRU_RECLAIM:
+			damon_acma_reclaim_stat = s->stat;
+			break;
+		default:
+			break;
+	}
+
+	return damon_acma_handle_commit_inputs();
+}
+
+static int damon_acma_after_wmarks_check(struct damon_ctx *c)
+{
+	return damon_acma_handle_commit_inputs();
+}
+
+static int __init damon_acma_init(void)
+{
+	int err = damon_modules_new_paddr_ctx_target(&ctx, &target);
+
+	if (err)
+		return err;
+
+	ctx->callback.after_wmarks_check = damon_acma_after_wmarks_check;
+	ctx->callback.after_aggregation = damon_acma_after_aggregation;
+
+	/* 'enabled' has set before this function, probably via command line */
+	if (enabled)
+		err = damon_acma_turn(true);
+
+	return err;
+}
+
+module_init(damon_acma_init);
-- 
2.39.2