[PATCH 0/5] mm/damon: add sample modules

[PATCH 0/5] mm/damon: add sample modules

[SeongJae Park]

DAMON provides API for other subsystems or modules in the kernel space.
The API functions have their own kernel-doc comments, but having working
example usages would further helps beginners.  There are DAMON modules
built using DAMON API, including DAMON_{SYSFS,RECLAIM,LRU_SORT}.  But
those are for real world usage rather than examples.  Add sample DAMON
modules for exasmple usages of DAMON API for beginners.

Changes from RFC
(https://lore.kernel.org/20241113162624.48973-1-sj@kernel.org)
- Add minimum age to prcl
- Wordsmith commit message
- Remove module_{license,author,description} that unnecessary for static modules

SeongJae Park (5):
  samples: add a skeleton of a sample DAMON module for working set size
    estimation
  samples/damon/wsse: start and stop DAMON as the user requests
  samples/damon/wsse: implement working set size estimation and logging
  samples/damon: introduce a skeleton of a smaple DAMON module for
    proactive reclamation
  samples/damon/prcl: implement schemes setup

 MAINTAINERS            |   1 +
 samples/Kconfig        |   2 +
 samples/Makefile       |   2 +
 samples/damon/Kconfig  |  30 +++++++++
 samples/damon/Makefile |   4 ++
 samples/damon/prcl.c   | 136 +++++++++++++++++++++++++++++++++++++++++
 samples/damon/wsse.c   | 116 +++++++++++++++++++++++++++++++++++
 7 files changed, 291 insertions(+)
 create mode 100644 samples/damon/Kconfig
 create mode 100644 samples/damon/Makefile
 create mode 100644 samples/damon/prcl.c
 create mode 100644 samples/damon/wsse.c


base-commit: d344b591933d7f56960f43d9c86effd14559f0f2
-- 
2.39.5

[PATCH 1/5] samples: add a skeleton of a sample DAMON module for working set size estimation

[SeongJae Park]

Add a skeleton for a sample DAMON static module that can be used for
estimating working set size of a given process.  Note that it is a
static module since DAMON is not exporting symbols to loadable modules
for now.  It exposes two module parameters, namely 'pid' and 'enable'.
'pid' will specify the process that the module will estimate the working
set size of.  'enable' will receive whether to start or stop the
estimation.  Because this is just a skeleton, the parameters do nothing,
though.  The functionalities will be implemented by following commits.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 MAINTAINERS            |  1 +
 samples/Kconfig        |  2 ++
 samples/Makefile       |  1 +
 samples/damon/Kconfig  | 17 +++++++++++
 samples/damon/Makefile |  3 ++
 samples/damon/wsse.c   | 65 ++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 89 insertions(+)
 create mode 100644 samples/damon/Kconfig
 create mode 100644 samples/damon/Makefile
 create mode 100644 samples/damon/wsse.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 1e930c7a58b1..68d825a4c69c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6328,6 +6328,7 @@ F:	Documentation/mm/damon/
 F:	include/linux/damon.h
 F:	include/trace/events/damon.h
 F:	mm/damon/
+F:	samples/damon/
 F:	tools/testing/selftests/damon/
 
 DAVICOM FAST ETHERNET (DMFE) NETWORK DRIVER
diff --git a/samples/Kconfig b/samples/Kconfig
index b288d9991d27..8d5a36f0e5d6 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -293,6 +293,8 @@ config SAMPLE_CGROUP
 
 source "samples/rust/Kconfig"
 
+source "samples/damon/Kconfig"
+
 endif # SAMPLES
 
 config HAVE_SAMPLE_FTRACE_DIRECT
diff --git a/samples/Makefile b/samples/Makefile
index b85fa64390c5..726bb5293486 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -39,3 +39,4 @@ obj-$(CONFIG_SAMPLE_KMEMLEAK)		+= kmemleak/
 obj-$(CONFIG_SAMPLE_CORESIGHT_SYSCFG)	+= coresight/
 obj-$(CONFIG_SAMPLE_FPROBE)		+= fprobe/
 obj-$(CONFIG_SAMPLES_RUST)		+= rust/
+obj-$(CONFIG_SAMPLE_DAMON_WSSE)		+= damon/
diff --git a/samples/damon/Kconfig b/samples/damon/Kconfig
new file mode 100644
index 000000000000..b799e01345c8
--- /dev/null
+++ b/samples/damon/Kconfig
@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: GPL-2.0
+
+menu "DAMON Samples"
+
+config SAMPLE_DAMON_WSSE
+	bool "DAMON sameple module for working set size estimation"
+	depends on DAMON && DAMON_VADDR
+	help
+	  This builds DAMON sample module for working set size estimation.
+
+	  The module receives a pid, monitor access to the virtual address
+	  space of the process, estimate working set size of the process, and
+	  repeatedly prints the size on the kernel log.
+
+	  If unsure, say N.
+
+endmenu
diff --git a/samples/damon/Makefile b/samples/damon/Makefile
new file mode 100644
index 000000000000..ccbe93d40130
--- /dev/null
+++ b/samples/damon/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_SAMPLE_DAMON_WSSE) += wsse.o
diff --git a/samples/damon/wsse.c b/samples/damon/wsse.c
new file mode 100644
index 000000000000..7f2cb76a1a70
--- /dev/null
+++ b/samples/damon/wsse.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * working set size estimation: monitor access pattern of given process and
+ * print estimated working set size (total size of regions that showing some
+ * access).
+ */
+
+#define pr_fmt(fmt) "damon_sample_wsse: " fmt
+
+#include <linux/damon.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+static int target_pid __read_mostly;
+module_param(target_pid, int, 0600);
+
+static int damon_sample_wsse_enable_store(
+		const char *val, const struct kernel_param *kp);
+
+static const struct kernel_param_ops enable_param_ops = {
+	.set = damon_sample_wsse_enable_store,
+	.get = param_get_bool,
+};
+
+static bool enable __read_mostly;
+module_param_cb(enable, &enable_param_ops, &enable, 0600);
+MODULE_PARM_DESC(enable, "Enable or disable DAMON_SAMPLE_WSSE");
+
+static int damon_sample_wsse_start(void)
+{
+	pr_info("start\n");
+	return 0;
+}
+
+static void damon_sample_wsse_stop(void)
+{
+	pr_info("stop\n");
+}
+
+static int damon_sample_wsse_enable_store(
+		const char *val, const struct kernel_param *kp)
+{
+	bool enabled = enable;
+	int err;
+
+	err = kstrtobool(val, &enable);
+	if (err)
+		return err;
+
+	if (enable == enabled)
+		return 0;
+
+	if (enable)
+		return damon_sample_wsse_start();
+	damon_sample_wsse_stop();
+	return 0;
+}
+
+static int __init damon_sample_wsse_init(void)
+{
+	return 0;
+}
+
+module_init(damon_sample_wsse_init);
-- 
2.39.5

[PATCH 2/5] samples/damon/wsse: start and stop DAMON as the user requests

[SeongJae Park]

Start running DAMON to monitor accesses of a process that the user
specified via 'target_pid' parameter, when 'y' is passed to 'enable'
parameter.  Stop running DAMON when 'n' is passed to 'enable' parameter.
Estimating the working set size from DAMON's monitoring results and
reporting it to the user will be implemented by the following commit.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 samples/damon/wsse.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/samples/damon/wsse.c b/samples/damon/wsse.c
index 7f2cb76a1a70..2ba0c91baad9 100644
--- a/samples/damon/wsse.c
+++ b/samples/damon/wsse.c
@@ -27,15 +27,48 @@ static bool enable __read_mostly;
 module_param_cb(enable, &enable_param_ops, &enable, 0600);
 MODULE_PARM_DESC(enable, "Enable or disable DAMON_SAMPLE_WSSE");
 
+static struct damon_ctx *ctx;
+static struct pid *target_pidp;
+
 static int damon_sample_wsse_start(void)
 {
+	struct damon_target *target;
+
 	pr_info("start\n");
-	return 0;
+
+	ctx = damon_new_ctx();
+	if (!ctx)
+		return -ENOMEM;
+	if (damon_select_ops(ctx, DAMON_OPS_VADDR)) {
+		damon_destroy_ctx(ctx);
+		return -EINVAL;
+	}
+
+	target = damon_new_target();
+	if (!target) {
+		damon_destroy_ctx(ctx);
+		return -ENOMEM;
+	}
+	damon_add_target(ctx, target);
+	target_pidp = find_get_pid(target_pid);
+	if (!target_pidp) {
+		damon_destroy_ctx(ctx);
+		return -EINVAL;
+	}
+	target->pid = target_pidp;
+
+	return damon_start(&ctx, 1, true);
 }
 
 static void damon_sample_wsse_stop(void)
 {
 	pr_info("stop\n");
+	if (ctx) {
+		damon_stop(&ctx, 1);
+		damon_destroy_ctx(ctx);
+	}
+	if (target_pidp)
+		put_pid(target_pidp);
 }
 
 static int damon_sample_wsse_enable_store(
-- 
2.39.5

[PATCH 3/5] samples/damon/wsse: implement working set size estimation and logging

[SeongJae Park]

Implement the DAMON-based working set size estimation logic.  The logic
iterates memory regions in DAMON-generated access pattern snapshot for
every aggregation interval and get the total sum of the size of any
region having one or higher 'nr_accesses' count.  That is, it assumes
any region having one or higher 'nr_accesses' to be a part of the
working set.  The estimated value is reported to the user by printing it
to the kernel log.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 samples/damon/wsse.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/samples/damon/wsse.c b/samples/damon/wsse.c
index 2ba0c91baad9..11be25803274 100644
--- a/samples/damon/wsse.c
+++ b/samples/damon/wsse.c
@@ -30,6 +30,23 @@ MODULE_PARM_DESC(enable, "Enable or disable DAMON_SAMPLE_WSSE");
 static struct damon_ctx *ctx;
 static struct pid *target_pidp;
 
+static int damon_sample_wsse_after_aggregate(struct damon_ctx *c)
+{
+	struct damon_target *t;
+
+	damon_for_each_target(t, c) {
+		struct damon_region *r;
+		unsigned long wss = 0;
+
+		damon_for_each_region(r, t) {
+			if (r->nr_accesses > 0)
+				wss += r->ar.end - r->ar.start;
+		}
+		pr_info("wss: %lu\n", wss);
+	}
+	return 0;
+}
+
 static int damon_sample_wsse_start(void)
 {
 	struct damon_target *target;
@@ -57,6 +74,7 @@ static int damon_sample_wsse_start(void)
 	}
 	target->pid = target_pidp;
 
+	ctx->callback.after_aggregation = damon_sample_wsse_after_aggregate;
 	return damon_start(&ctx, 1, true);
 }
 
-- 
2.39.5

[PATCH 4/5] samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation

[SeongJae Park]

DAMON is not only for monitoring of access patterns, but also for
access-aware system operations.  For the system operations, DAMON
provides a feature called DAMOS (Data Access Monitoring-based Operation
Schemes).  There is no sample API usage of DAMOS, though.  Copy the
working set size estimation sample modules with changed names of the
module and symbols, to use it as a skeleton for a sample module showing
the DAMOS API usage.  The following commit will make it proactively
reclaim cold memory of the given process, using DAMOS.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 samples/Makefile       |   1 +
 samples/damon/Kconfig  |  13 +++++
 samples/damon/Makefile |   1 +
 samples/damon/prcl.c   | 116 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 131 insertions(+)
 create mode 100644 samples/damon/prcl.c

diff --git a/samples/Makefile b/samples/Makefile
index 726bb5293486..5af6bb8afb07 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -40,3 +40,4 @@ obj-$(CONFIG_SAMPLE_CORESIGHT_SYSCFG)	+= coresight/
 obj-$(CONFIG_SAMPLE_FPROBE)		+= fprobe/
 obj-$(CONFIG_SAMPLES_RUST)		+= rust/
 obj-$(CONFIG_SAMPLE_DAMON_WSSE)		+= damon/
+obj-$(CONFIG_SAMPLE_DAMON_PRCL)		+= damon/
diff --git a/samples/damon/Kconfig b/samples/damon/Kconfig
index b799e01345c8..63f6dcd71daa 100644
--- a/samples/damon/Kconfig
+++ b/samples/damon/Kconfig
@@ -14,4 +14,17 @@ config SAMPLE_DAMON_WSSE
 
 	  If unsure, say N.
 
+config SAMPLE_DAMON_PRCL
+	bool "DAMON sameple module for access-aware proactive reclamation"
+	depends on DAMON && DAMON_VADDR
+	help
+	  This builds DAMON sample module for access-aware proactive
+	  reclamation.
+
+	  The module receives a pid, monitor access to the virtual address
+	  space of the process, find memory regions that not accessed, and
+	  proactively reclaim the regions.
+
+	  If unsure, say N.
+
 endmenu
diff --git a/samples/damon/Makefile b/samples/damon/Makefile
index ccbe93d40130..7f155143f237 100644
--- a/samples/damon/Makefile
+++ b/samples/damon/Makefile
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
 
 obj-$(CONFIG_SAMPLE_DAMON_WSSE) += wsse.o
+obj-$(CONFIG_SAMPLE_DAMON_PRCL) += prcl.o
diff --git a/samples/damon/prcl.c b/samples/damon/prcl.c
new file mode 100644
index 000000000000..b34b9bfed532
--- /dev/null
+++ b/samples/damon/prcl.c
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * proactive reclamation: monitor access pattern of a given process, find
+ * regiosn that seems not accessed, and proactively page out the regions.
+ */
+
+#define pr_fmt(fmt) "damon_sample_prcl: " fmt
+
+#include <linux/damon.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+static int target_pid __read_mostly;
+module_param(target_pid, int, 0600);
+
+static int damon_sample_prcl_enable_store(
+		const char *val, const struct kernel_param *kp);
+
+static const struct kernel_param_ops enable_param_ops = {
+	.set = damon_sample_prcl_enable_store,
+	.get = param_get_bool,
+};
+
+static bool enable __read_mostly;
+module_param_cb(enable, &enable_param_ops, &enable, 0600);
+MODULE_PARM_DESC(enable, "Enable of disable DAMON_SAMPLE_WSSE");
+
+static struct damon_ctx *ctx;
+static struct pid *target_pidp;
+
+static int damon_sample_prcl_after_aggregate(struct damon_ctx *c)
+{
+	struct damon_target *t;
+
+	damon_for_each_target(t, c) {
+		struct damon_region *r;
+		unsigned long wss = 0;
+
+		damon_for_each_region(r, t) {
+			if (r->nr_accesses > 0)
+				wss += r->ar.end - r->ar.start;
+		}
+		pr_info("wss: %lu\n", wss);
+	}
+	return 0;
+}
+
+static int damon_sample_prcl_start(void)
+{
+	struct damon_target *target;
+
+	pr_info("start\n");
+
+	ctx = damon_new_ctx();
+	if (!ctx)
+		return -ENOMEM;
+	if (damon_select_ops(ctx, DAMON_OPS_VADDR)) {
+		damon_destroy_ctx(ctx);
+		return -EINVAL;
+	}
+
+	target = damon_new_target();
+	if (!target) {
+		damon_destroy_ctx(ctx);
+		return -ENOMEM;
+	}
+	damon_add_target(ctx, target);
+	target_pidp = find_get_pid(target_pid);
+	if (!target_pidp) {
+		damon_destroy_ctx(ctx);
+		return -EINVAL;
+	}
+	target->pid = target_pidp;
+
+	ctx->callback.after_aggregation = damon_sample_prcl_after_aggregate;
+
+	return damon_start(&ctx, 1, true);
+}
+
+static void damon_sample_prcl_stop(void)
+{
+	pr_info("stop\n");
+	if (ctx) {
+		damon_stop(&ctx, 1);
+		damon_destroy_ctx(ctx);
+	}
+	if (target_pidp)
+		put_pid(target_pidp);
+}
+
+static int damon_sample_prcl_enable_store(
+		const char *val, const struct kernel_param *kp)
+{
+	bool enabled = enable;
+	int err;
+
+	err = kstrtobool(val, &enable);
+	if (err)
+		return err;
+
+	if (enable == enabled)
+		return 0;
+
+	if (enable)
+		return damon_sample_prcl_start();
+	damon_sample_prcl_stop();
+	return 0;
+}
+
+static int __init damon_sample_prcl_init(void)
+{
+	return 0;
+}
+
+module_init(damon_sample_prcl_init);
-- 
2.39.5

[PATCH 5/5] samples/damon/prcl: implement schemes setup

[SeongJae Park]

Implement a proactive cold memory regions reclaiming logic of prcl
sample module using DAMOS.  The logic treats memory regions that not
accessed at all for five or more seconds as cold, and reclaim those as
soon as found.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 samples/damon/prcl.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/samples/damon/prcl.c b/samples/damon/prcl.c
index b34b9bfed532..c3acbdab7a62 100644
--- a/samples/damon/prcl.c
+++ b/samples/damon/prcl.c
@@ -49,6 +49,7 @@ static int damon_sample_prcl_after_aggregate(struct damon_ctx *c)
 static int damon_sample_prcl_start(void)
 {
 	struct damon_target *target;
+	struct damos *scheme;
 
 	pr_info("start\n");
 
@@ -75,6 +76,25 @@ static int damon_sample_prcl_start(void)
 
 	ctx->callback.after_aggregation = damon_sample_prcl_after_aggregate;
 
+	scheme = damon_new_scheme(
+			&(struct damos_access_pattern) {
+			.min_sz_region = PAGE_SIZE,
+			.max_sz_region = ULONG_MAX,
+			.min_nr_accesses = 0,
+			.max_nr_accesses = 0,
+			.min_age_region = 50,
+			.max_age_region = UINT_MAX},
+			DAMOS_PAGEOUT,
+			0,
+			&(struct damos_quota){},
+			&(struct damos_watermarks){},
+			NUMA_NO_NODE);
+	if (!scheme) {
+		damon_destroy_ctx(ctx);
+		return -ENOMEM;
+	}
+	damon_set_schemes(ctx, &scheme, 1);
+
 	return damon_start(&ctx, 1, true);
 }
 
-- 
2.39.5