[PATCH 00/20] mm/damon: let DAMOS feeds and tame/auto-tune itself

[PATCH 00/20] mm/damon: let DAMOS feeds and tame/auto-tune itself

[SeongJae Park]

The Aim-oriented Feedback-driven DAMOS Aggressiveness Auto-tuning
patchset[1] which has merged since commit 9294a037c015 ("mm/damon/core:
implement goal-oriented feedback-driven quota auto-tuning") made the
mechanism and the policy separated.  That is, users can set a part of
DAMOS control policies without a deep understanding of the mechanism but
just their demands such as SLA.

However, users are still required to do some additional work of manually
collecting their target metric and feeding it to DAMOS.  In the case of
end-users who use DAMON sysfs interface, the context switches between
user-space and kernel-space could also make it inefficient.  The
overhead is supposed to be only trivial in common cases, though.
Meanwhile, in simple use cases, the target metric could be common system
metrics that the kernel can efficiently self-retrieve, such as memory
pressure stall time (PSI).

Extend DAMOS quota auto-tuning to support multiple types of metrics
including the DAMOS self-retrievable ones, and add support for memory
pressure stall time metric.  Different types of metrics can be supported
in future.  The auto-tuning capability is currently supported for only
users of DAMOS kernel API and DAMON sysfs interface.  Extend the support
to DAMON_RECLAIM.

Patches Sequence
================

First five patches are for helping debugging and fine-tuning existing
quota control features.  The first one (patch 1) exposes the effective
quota that is made with given user inputs to DAMOS kernel API users
and kernel-doc documents.  Following four patches implement (patches 1, 2
and 3) and document (patches 4 and 5) a new DAMON sysfs file that
exposes the value.

Following six patches cleanup and simplify the existing DAMOS quota
auto-tuning code by improving layout of comments and data structures
(patches 6 and 7), supporting common use cases, namely multiple goals
(patches 8, 9 and 10), and simplifying the interface (patch 11).

Then six patches for the main purpose of this patchset follow.  The
first three changes extend the core logic for various target metrics
(patch 12), implement memory pressure stall time-based target metric
support (patch 13), and update DAMON sysfs interface to support the new
target metric (patch 14).  Then, documentation updates for the features
on design (patch 15), ABI (patch 16), and usage (patch 17) follow.

Last three patches add auto-tuning support on DAMON_RECLAIM.  The
patches implement DAMON_RECLAIM parameters for user-feedback driven
quota auto-tuning (patch 18), memory pressure stall time-driven quota
self-tuning (patch 19), and finally update the DAMON_RECLAIM usage
document for the new parameters (patch 20).

[1] https://lore.kernel.org/all/20231130023652.50284-1-sj@kernel.org/

SeongJae Park (20):
  mm/damon/core: Set damos_quota->esz as public field and document
  mm/damon/sysfs-schemes: implement quota effective_bytes file
  mm/damon/sysfs: implement a kdamond command for updating schemes'
    effective quotas
  Docs/ABI/damon: document effective_bytes sysfs file
  Docs/admin-guide/mm/damon/usage: document effective_bytes file
  mm/damon: move comments and fields for damos-quota-prioritization to
    the end
  mm/damon/core: split out quota goal related fields to a struct
  mm/damon/core: add multiple goals per damos_quota and helpers for
    those
  mm/damon/sysfs: use only quota->goals
  mm/damon/core: remove ->goal field of damos_quota
  mm/damon/core: let goal specified with only target and current values
  mm/damon/core: support multiple metrics for quota goal
  mm/damon/core: implement PSI metric DAMOS quota goal
  mm/damon/sysfs-schemes: support PSI-based quota auto-tune
  Docs/mm/damon/design: document quota goal self-tuning
  Docs/ABI/damon: document quota goal metric file
  Docs/admin-guide/mm/damon/usage: document quota goal metric file
  mm/damon/reclaim: implement user-feedback driven quota auto-tuning
  mm/damon/reclaim: implement memory PSI-driven quota self-tuning
  Docs/admin-guide/mm/damon/reclaim: document auto-tuning parameters

 .../ABI/testing/sysfs-kernel-mm-damon         |  16 ++-
 .../admin-guide/mm/damon/reclaim.rst          |  27 ++++
 Documentation/admin-guide/mm/damon/usage.rst  |  31 +++--
 Documentation/mm/damon/design.rst             |  20 ++-
 include/linux/damon.h                         |  89 ++++++++++---
 mm/damon/core.c                               | 120 +++++++++++++++--
 mm/damon/reclaim.c                            |  53 ++++++++
 mm/damon/sysfs-common.h                       |   6 +-
 mm/damon/sysfs-schemes.c                      | 124 +++++++++++++++---
 mm/damon/sysfs.c                              |  33 ++++-
 10 files changed, 454 insertions(+), 65 deletions(-)


base-commit: ecd6af887705c19e7367f9d3818ae712f4674168
-- 
2.39.2

[PATCH 01/20] mm/damon/core: Set damos_quota->esz as public field and document

[SeongJae Park]

DAMOS allow users to specify the quota as they want in multiple ways
including time quota, size quota, and feedback-based auto-tuning.  DAMOS
makes one effective quota out of the inputs and use it at the end.
Knowing the current effective quota helps understanding DAMOS' internal
mechanism and fine-tuning quotas.  DAMON kernel API users can get the
information from ->esz field of damos_quota struct, but the field is
marked as private purpose, and not kernel-doc documented.  Make it
public and document.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h | 6 ++++--
 mm/damon/core.c       | 8 ++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 5881e4ac30be..93ef45b87b9c 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -138,6 +138,7 @@ enum damos_action {
  *
  * @get_score:		Feedback function for self-tuning quota.
  * @get_score_arg:	Parameter for @get_score
+ * @esz:		Effective size quota in bytes.
  *
  * To avoid consuming too much CPU time or IO resources for applying the
  * &struct damos->action to large memory, DAMON allows users to set time and/or
@@ -167,6 +168,8 @@ enum damos_action {
  * tuning is getting the feedback screo value of 10,000.  If @ms and/or @sz are
  * set together, those work as a hard limit quota.  If neither @ms nor @sz are
  * set, the mechanism starts from the quota of one byte.
+ *
+ * The resulting effective size quota in bytes is set to @esz.
  */
 struct damos_quota {
 	unsigned long ms;
@@ -179,14 +182,13 @@ struct damos_quota {
 
 	unsigned long (*get_score)(void *arg);
 	void *get_score_arg;
+	unsigned long esz;
 
 /* private: */
 	/* For throughput estimation */
 	unsigned long total_charged_sz;
 	unsigned long total_charged_ns;
 
-	unsigned long esz;	/* Effective size quota in bytes */
-
 	/* For charging the quota */
 	unsigned long charged_sz;
 	unsigned long charged_from;
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 5b325749fc12..0656966a6fc4 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -299,12 +299,12 @@ void damos_destroy_filter(struct damos_filter *f)
 	damos_free_filter(f);
 }
 
-/* initialize private fields of damos_quota and return the pointer */
-static struct damos_quota *damos_quota_init_priv(struct damos_quota *quota)
+/* initialize fields of @quota that normally API users wouldn't set */
+static struct damos_quota *damos_quota_init(struct damos_quota *quota)
 {
+	quota->esz = 0;
 	quota->total_charged_sz = 0;
 	quota->total_charged_ns = 0;
-	quota->esz = 0;
 	quota->charged_sz = 0;
 	quota->charged_from = 0;
 	quota->charge_target_from = NULL;
@@ -336,7 +336,7 @@ struct damos *damon_new_scheme(struct damos_access_pattern *pattern,
 	scheme->stat = (struct damos_stat){};
 	INIT_LIST_HEAD(&scheme->list);
 
-	scheme->quota = *(damos_quota_init_priv(quota));
+	scheme->quota = *(damos_quota_init(quota));
 
 	scheme->wmarks = *wmarks;
 	scheme->wmarks.activated = true;
-- 
2.39.2

[PATCH 02/20] mm/damon/sysfs-schemes: implement quota effective_bytes file

[SeongJae Park]

DAMON sysfs interface allows users to set two types of quotas, namely
time quota and size quota.  DAMOS converts time quota to a size quota
and use smaller one among the resulting two size quotas.  The resulting
effective size quota can be helpful for debugging and analysis, but not
exposed to the user.  The recently added feedback-driven quota
auto-tuning is making it even more mysterious.

Implement a DAMON sysfs interface read-only empty file, namely
'effective_bytes', under the quota goal DAMON sysfs directory.  It will
be extended to expose the effective quota to the end user.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-schemes.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index f6c7f43f06cc..dd46b2db5455 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1139,6 +1139,7 @@ struct damon_sysfs_quotas {
 	unsigned long ms;
 	unsigned long sz;
 	unsigned long reset_interval_ms;
+	unsigned long effective_sz;	/* Effective size quota in bytes */
 };
 
 static struct damon_sysfs_quotas *damon_sysfs_quotas_alloc(void)
@@ -1252,6 +1253,15 @@ static ssize_t reset_interval_ms_store(struct kobject *kobj,
 	return count;
 }
 
+static ssize_t effective_bytes_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_quotas *quotas = container_of(kobj,
+			struct damon_sysfs_quotas, kobj);
+
+	return sysfs_emit(buf, "%lu\n", quotas->effective_sz);
+}
+
 static void damon_sysfs_quotas_release(struct kobject *kobj)
 {
 	kfree(container_of(kobj, struct damon_sysfs_quotas, kobj));
@@ -1266,10 +1276,14 @@ static struct kobj_attribute damon_sysfs_quotas_sz_attr =
 static struct kobj_attribute damon_sysfs_quotas_reset_interval_ms_attr =
 		__ATTR_RW_MODE(reset_interval_ms, 0600);
 
+static struct kobj_attribute damon_sysfs_quotas_effective_bytes_attr =
+		__ATTR_RO_MODE(effective_bytes, 0400);
+
 static struct attribute *damon_sysfs_quotas_attrs[] = {
 	&damon_sysfs_quotas_ms_attr.attr,
 	&damon_sysfs_quotas_sz_attr.attr,
 	&damon_sysfs_quotas_reset_interval_ms_attr.attr,
+	&damon_sysfs_quotas_effective_bytes_attr.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(damon_sysfs_quotas);
-- 
2.39.2

[PATCH 03/20] mm/damon/sysfs: implement a kdamond command for updating schemes' effective quotas

[SeongJae Park]

Implement yet another kdamond 'state' file input command, namely
'update_schemes_effective_quotas'.  If it is written, the
'effective_bytes' files of the kdamond will be updated to provide the
current effective size quota of each scheme in bytes.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-common.h  |  4 ++++
 mm/damon/sysfs-schemes.c | 20 ++++++++++++++++++++
 mm/damon/sysfs.c         | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 56 insertions(+)

diff --git a/mm/damon/sysfs-common.h b/mm/damon/sysfs-common.h
index ec0703e1e90b..5a1ac15fb2f8 100644
--- a/mm/damon/sysfs-common.h
+++ b/mm/damon/sysfs-common.h
@@ -61,3 +61,7 @@ int damon_sysfs_schemes_clear_regions(
 
 void damos_sysfs_set_quota_scores(struct damon_sysfs_schemes *sysfs_schemes,
 		struct damon_ctx *ctx);
+
+void damos_sysfs_update_effective_quotas(
+		struct damon_sysfs_schemes *sysfs_schemes,
+		struct damon_ctx *ctx);
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index dd46b2db5455..9d90e7b757b7 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1930,6 +1930,26 @@ void damos_sysfs_set_quota_scores(struct damon_sysfs_schemes *sysfs_schemes,
 	}
 }
 
+void damos_sysfs_update_effective_quotas(
+		struct damon_sysfs_schemes *sysfs_schemes,
+		struct damon_ctx *ctx)
+{
+	struct damos *scheme;
+	int schemes_idx = 0;
+
+	damon_for_each_scheme(scheme, ctx) {
+		struct damon_sysfs_quotas *sysfs_quotas;
+
+		/* user could have removed the scheme sysfs dir */
+		if (schemes_idx >= sysfs_schemes->nr)
+			break;
+
+		sysfs_quotas =
+			sysfs_schemes->schemes_arr[schemes_idx++]->quotas;
+		sysfs_quotas->effective_sz = scheme->quota.esz;
+	}
+}
+
 static struct damos *damon_sysfs_mk_scheme(
 		struct damon_sysfs_scheme *sysfs_scheme)
 {
diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index 678de97fcc88..cc2d88a901f4 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -1019,6 +1019,11 @@ enum damon_sysfs_cmd {
 	 * regions
 	 */
 	DAMON_SYSFS_CMD_CLEAR_SCHEMES_TRIED_REGIONS,
+	/*
+	 * @DAMON_SYSFS_CMD_UPDATE_SCHEMES_EFFECTIVE_QUOTAS: Update the
+	 * effective size quota of the scheme in bytes.
+	 */
+	DAMON_SYSFS_CMD_UPDATE_SCHEMES_EFFECTIVE_QUOTAS,
 	/*
 	 * @NR_DAMON_SYSFS_CMDS: Total number of DAMON sysfs commands.
 	 */
@@ -1035,6 +1040,7 @@ static const char * const damon_sysfs_cmd_strs[] = {
 	"update_schemes_tried_bytes",
 	"update_schemes_tried_regions",
 	"clear_schemes_tried_regions",
+	"update_schemes_effective_quotas",
 };
 
 /*
@@ -1375,6 +1381,29 @@ static int damon_sysfs_commit_schemes_quota_goals(
 	return 0;
 }
 
+/*
+ * damon_sysfs_upd_schemes_effective_quotas() - Update schemes effective quotas
+ * sysfs files.
+ * @kdamond:	The kobject wrapper that associated to the kdamond thread.
+ *
+ * This function reads the schemes' effective quotas of specific kdamond and
+ * update the related values for sysfs files.  This function should be called
+ * from DAMON callbacks while holding ``damon_syfs_lock``, to safely access the
+ * DAMON contexts-internal data and DAMON sysfs variables.
+ */
+static int damon_sysfs_upd_schemes_effective_quotas(
+		struct damon_sysfs_kdamond *kdamond)
+{
+	struct damon_ctx *ctx = kdamond->damon_ctx;
+
+	if (!ctx)
+		return -EINVAL;
+	damos_sysfs_update_effective_quotas(
+			kdamond->contexts->contexts_arr[0]->schemes, ctx);
+	return 0;
+}
+
+
 /*
  * damon_sysfs_cmd_request_callback() - DAMON callback for handling requests.
  * @c:		The DAMON context of the callback.
@@ -1437,6 +1466,9 @@ static int damon_sysfs_cmd_request_callback(struct damon_ctx *c, bool active,
 	case DAMON_SYSFS_CMD_CLEAR_SCHEMES_TRIED_REGIONS:
 		err = damon_sysfs_clear_schemes_regions(kdamond);
 		break;
+	case DAMON_SYSFS_CMD_UPDATE_SCHEMES_EFFECTIVE_QUOTAS:
+		err = damon_sysfs_upd_schemes_effective_quotas(kdamond);
+		break;
 	default:
 		break;
 	}
-- 
2.39.2

[PATCH 04/20] Docs/ABI/damon: document effective_bytes sysfs file

[SeongJae Park]

Update the DAMON ABI doc for the effective_bytes sysfs file and the
kdamond state file input command for updating the content of the file.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/ABI/testing/sysfs-kernel-mm-damon | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-damon b/Documentation/ABI/testing/sysfs-kernel-mm-damon
index bfa5b8288d8d..a1e4fdb04f95 100644
--- a/Documentation/ABI/testing/sysfs-kernel-mm-damon
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-damon
@@ -34,7 +34,9 @@ Description:	Writing 'on' or 'off' to this file makes the kdamond starts or
 		kdamond.  Writing 'update_schemes_tried_bytes' to the file
 		updates only '.../tried_regions/total_bytes' files of this
 		kdamond.  Writing 'clear_schemes_tried_regions' to the file
-		removes contents of the 'tried_regions' directory.
+		removes contents of the 'tried_regions' directory.  Writing
+		'update_schemes_effective_quotas' to the file updates
+		'.../quotas/effective_bytes' files of this kdamond.
 
 What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/pid
 Date:		Mar 2022
@@ -208,6 +210,12 @@ Contact:	SeongJae Park <sj@kernel.org>
 Description:	Writing to and reading from this file sets and gets the size
 		quota of the scheme in bytes.
 
+What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/quotas/effective_bytes
+Date:		Feb 2024
+Contact:	SeongJae Park <sj@kernel.org>
+Description:	Reading from this file gets the effective size quota of the
+		scheme in bytes, which adjusted for the time quota and goals.
+
 What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/quotas/reset_interval_ms
 Date:		Mar 2022
 Contact:	SeongJae Park <sj@kernel.org>
-- 
2.39.2

[PATCH 05/20] Docs/admin-guide/mm/damon/usage: document effective_bytes file

[SeongJae Park]

Update DAMON usage document for the effective quota file of the DAMON
sysfs interface.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/usage.rst | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index db6620b5bc0a..220ebbde7324 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -83,7 +83,7 @@ comma (",").
     │ │ │ │ │ │ │ │ sz/min,max
     │ │ │ │ │ │ │ │ nr_accesses/min,max
     │ │ │ │ │ │ │ │ age/min,max
-    │ │ │ │ │ │ │ :ref:`quotas <sysfs_quotas>`/ms,bytes,reset_interval_ms
+    │ │ │ │ │ │ │ :ref:`quotas <sysfs_quotas>`/ms,bytes,reset_interval_ms,effective_bytes
     │ │ │ │ │ │ │ │ weights/sz_permil,nr_accesses_permil,age_permil
     │ │ │ │ │ │ │ │ :ref:`goals <sysfs_schemes_quota_goals>`/nr_goals
     │ │ │ │ │ │ │ │ │ 0/target_value,current_value
@@ -153,6 +153,9 @@ Users can write below commands for the kdamond to the ``state`` file.
 - ``clear_schemes_tried_regions``: Clear the DAMON-based operating scheme
   action tried regions directory for each DAMON-based operation scheme of the
   kdamond.
+- ``update_schemes_effective_bytes``: Update the contents of
+  ``effective_bytes`` files for each DAMON-based operation scheme of the
+  kdamond.  For more details, refer to :ref:`quotas directory <sysfs_quotas>`.
 
 If the state is ``on``, reading ``pid`` shows the pid of the kdamond thread.
 
@@ -320,8 +323,9 @@ schemes/<N>/quotas/
 The directory for the :ref:`quotas <damon_design_damos_quotas>` of the given
 DAMON-based operation scheme.
 
-Under ``quotas`` directory, three files (``ms``, ``bytes``,
-``reset_interval_ms``) and two directores (``weights`` and ``goals``) exist.
+Under ``quotas`` directory, four files (``ms``, ``bytes``,
+``reset_interval_ms``, ``effective_bytes``) and two directores (``weights`` and
+``goals``) exist.
 
 You can set the ``time quota`` in milliseconds, ``size quota`` in bytes, and
 ``reset interval`` in milliseconds by writing the values to the three files,
@@ -332,6 +336,15 @@ apply the action to only up to ``bytes`` bytes of memory regions within the
 quota limits unless at least one :ref:`goal <sysfs_schemes_quota_goals>` is
 set.
 
+The time quota is internally transformed to a size quota.  Between the
+transformed size quota and user-specified size quota, smaller one is applied.
+Based on the user-specified :ref:`goal <sysfs_schemes_quota_goals>`, the
+effective size quota is further adjusted.  Reading ``effective_bytes`` returns
+the current effective size quota.  The file is not updated in real time, so
+users should ask DAMON sysfs interface to update the content of the file for
+the stats by writing a special keyword, ``update_schemes_effective_bytes`` to
+the relevant ``kdamonds/<N>/state`` file.
+
 Under ``weights`` directory, three files (``sz_permil``,
 ``nr_accesses_permil``, and ``age_permil``) exist.
 You can set the :ref:`prioritization weights
-- 
2.39.2

[PATCH 06/20] mm/damon: move comments and fields for damos-quota-prioritization to the end

[SeongJae Park]

The comments and definition of 'struct damos_quota' lists a few fields
for effective quota generation first, fields for regions prioritization
under the quota, and then remaining fields for effective quota
generation.  Readers' should unnecesssarily switch their context in the
middle.  List all the fields for the effective quota first, and then
fields for the prioritization for making it easier to read.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h | 30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 93ef45b87b9c..bd17b14828bc 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -128,18 +128,17 @@ enum damos_action {
 
 /**
  * struct damos_quota - Controls the aggressiveness of the given scheme.
+ * @reset_interval:	Charge reset interval in milliseconds.
  * @ms:			Maximum milliseconds that the scheme can use.
  * @sz:			Maximum bytes of memory that the action can be applied.
- * @reset_interval:	Charge reset interval in milliseconds.
+ * @get_score:		Feedback function for self-tuning quota.
+ * @get_score_arg:	Parameter for @get_score
+ * @esz:		Effective size quota in bytes.
  *
  * @weight_sz:		Weight of the region's size for prioritization.
  * @weight_nr_accesses:	Weight of the region's nr_accesses for prioritization.
  * @weight_age:		Weight of the region's age for prioritization.
  *
- * @get_score:		Feedback function for self-tuning quota.
- * @get_score_arg:	Parameter for @get_score
- * @esz:		Effective size quota in bytes.
- *
  * To avoid consuming too much CPU time or IO resources for applying the
  * &struct damos->action to large memory, DAMON allows users to set time and/or
  * size quotas.  The quotas can be set by writing non-zero values to &ms and
@@ -152,12 +151,6 @@ enum damos_action {
  * throughput of the scheme's action.  DAMON then compares it against &sz and
  * uses smaller one as the effective quota.
  *
- * For selecting regions within the quota, DAMON prioritizes current scheme's
- * target memory regions using the &struct damon_operations->get_scheme_score.
- * You could customize the prioritization logic by setting &weight_sz,
- * &weight_nr_accesses, and &weight_age, because monitoring operations are
- * encouraged to respect those.
- *
  * If @get_score function pointer is set, DAMON calls it back with
  * @get_score_arg and get the return value of it for every @reset_interval.
  * Then, DAMON adjusts the effective quota using the return value as a feedback
@@ -170,20 +163,25 @@ enum damos_action {
  * set, the mechanism starts from the quota of one byte.
  *
  * The resulting effective size quota in bytes is set to @esz.
+ *
+ * For selecting regions within the quota, DAMON prioritizes current scheme's
+ * target memory regions using the &struct damon_operations->get_scheme_score.
+ * You could customize the prioritization logic by setting &weight_sz,
+ * &weight_nr_accesses, and &weight_age, because monitoring operations are
+ * encouraged to respect those.
  */
 struct damos_quota {
+	unsigned long reset_interval;
 	unsigned long ms;
 	unsigned long sz;
-	unsigned long reset_interval;
+	unsigned long (*get_score)(void *arg);
+	void *get_score_arg;
+	unsigned long esz;
 
 	unsigned int weight_sz;
 	unsigned int weight_nr_accesses;
 	unsigned int weight_age;
 
-	unsigned long (*get_score)(void *arg);
-	void *get_score_arg;
-	unsigned long esz;
-
 /* private: */
 	/* For throughput estimation */
 	unsigned long total_charged_sz;
-- 
2.39.2

[PATCH 07/20] mm/damon/core: split out quota goal related fields to a struct

[SeongJae Park]

'struct damos_quota' is not small now.  Split out fields for quota goal
to a separate struct for easier reading.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h    | 36 ++++++++++++++++++++++--------------
 mm/damon/core.c          | 13 +++++++------
 mm/damon/sysfs-schemes.c | 10 +++++-----
 3 files changed, 34 insertions(+), 25 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index bd17b14828bc..2fe345adf6b2 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -126,13 +126,28 @@ enum damos_action {
 	NR_DAMOS_ACTIONS,
 };
 
+/**
+ * struct damos_quota_goal - DAMOS scheme quota auto-tuning goal.
+ * @get_score:		Function for getting current score of the goal.
+ * @get_score_arg:	Parameter for @get_score
+ *
+ * Data structure for getting the current score of the quota tuning goal.
+ * Calling @get_score with @get_score_arg as the parameter should return the
+ * current score.  Then the score is entered to DAMON's internal feedback loop
+ * mechanism to get the auto-tuned quota.  The goal of the tuning is getting
+ * the feedback score value of 10,000.
+ */
+struct damos_quota_goal {
+	unsigned long (*get_score)(void *arg);
+	void *get_score_arg;
+};
+
 /**
  * struct damos_quota - Controls the aggressiveness of the given scheme.
  * @reset_interval:	Charge reset interval in milliseconds.
  * @ms:			Maximum milliseconds that the scheme can use.
  * @sz:			Maximum bytes of memory that the action can be applied.
- * @get_score:		Feedback function for self-tuning quota.
- * @get_score_arg:	Parameter for @get_score
+ * @goal:		Quota auto-tuning goal.
  * @esz:		Effective size quota in bytes.
  *
  * @weight_sz:		Weight of the region's size for prioritization.
@@ -151,16 +166,10 @@ enum damos_action {
  * throughput of the scheme's action.  DAMON then compares it against &sz and
  * uses smaller one as the effective quota.
  *
- * If @get_score function pointer is set, DAMON calls it back with
- * @get_score_arg and get the return value of it for every @reset_interval.
- * Then, DAMON adjusts the effective quota using the return value as a feedback
- * score to the current quota, using its internal feedback loop algorithm.
- *
- * The feedback loop algorithem assumes the quota input and the feedback score
- * output are in a positive proportional relationship, and the goal of the
- * tuning is getting the feedback screo value of 10,000.  If @ms and/or @sz are
- * set together, those work as a hard limit quota.  If neither @ms nor @sz are
- * set, the mechanism starts from the quota of one byte.
+ * If ->get_score field of @goal is set, DAMON calculates yet another size
+ * quota based on the goal using its internal feedback loop algorithm, for
+ * every @reset_interval.  Then, if the new size quota is smaller than the
+ * effective quota, it uses the new size quota as the effective quota.
  *
  * The resulting effective size quota in bytes is set to @esz.
  *
@@ -174,8 +183,7 @@ struct damos_quota {
 	unsigned long reset_interval;
 	unsigned long ms;
 	unsigned long sz;
-	unsigned long (*get_score)(void *arg);
-	void *get_score_arg;
+	struct damos_quota_goal goal;
 	unsigned long esz;
 
 	unsigned int weight_sz;
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 0656966a6fc4..fe4209672121 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1083,21 +1083,22 @@ static unsigned long damon_feed_loop_next_input(unsigned long last_input,
 	return min_input;
 }
 
-/* Shouldn't be called if quota->ms, quota->sz, and quota->get_score unset */
+/* Called only if quota->ms, quota->sz, or quota->goal.get_score are set */
 static void damos_set_effective_quota(struct damos_quota *quota)
 {
 	unsigned long throughput;
 	unsigned long esz;
 
-	if (!quota->ms && !quota->get_score) {
+	if (!quota->ms && !quota->goal.get_score) {
 		quota->esz = quota->sz;
 		return;
 	}
 
-	if (quota->get_score) {
+	if (quota->goal.get_score) {
 		quota->esz_bp = damon_feed_loop_next_input(
 				max(quota->esz_bp, 10000UL),
-				quota->get_score(quota->get_score_arg));
+				quota->goal.get_score(
+					quota->goal.get_score_arg));
 		esz = quota->esz_bp / 10000;
 	}
 
@@ -1107,7 +1108,7 @@ static void damos_set_effective_quota(struct damos_quota *quota)
 				quota->total_charged_ns;
 		else
 			throughput = PAGE_SIZE * 1024;
-		if (quota->get_score)
+		if (quota->goal.get_score)
 			esz = min(throughput * quota->ms, esz);
 		else
 			esz = throughput * quota->ms;
@@ -1127,7 +1128,7 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s)
 	unsigned long cumulated_sz;
 	unsigned int score, max_score = 0;
 
-	if (!quota->ms && !quota->sz && !quota->get_score)
+	if (!quota->ms && !quota->sz && !quota->goal.get_score)
 		return;
 
 	/* New charge window starts */
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 9d90e7b757b7..85ef58f98a87 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1894,19 +1894,19 @@ static void damos_sysfs_set_quota_score(
 	struct damos_sysfs_quota_goal *sysfs_goal;
 	int i;
 
-	quota->get_score = NULL;
-	quota->get_score_arg = (void *)0;
+	quota->goal.get_score = NULL;
+	quota->goal.get_score_arg = (void *)0;
 	for (i = 0; i < sysfs_goals->nr; i++) {
 		sysfs_goal = sysfs_goals->goals_arr[i];
 		if (!sysfs_goal->target_value)
 			continue;
 
 		/* Higher score makes scheme less aggressive */
-		quota->get_score_arg = (void *)max(
-				(unsigned long)quota->get_score_arg,
+		quota->goal.get_score_arg = (void *)max(
+				(unsigned long)quota->goal.get_score_arg,
 				sysfs_goal->current_value * 10000 /
 				sysfs_goal->target_value);
-		quota->get_score = damos_sysfs_get_quota_score;
+		quota->goal.get_score = damos_sysfs_get_quota_score;
 	}
 }
 
-- 
2.39.2

[PATCH 08/20] mm/damon/core: add multiple goals per damos_quota and helpers for those

[SeongJae Park]

The feedback-driven DAMOS quota auto-tuning feature allows only single
goal to the DAMON kernel API users.  The API users could implement
multiple goals for the end-users on their level, and that's what DAMON
sysfs interface is doing.  More DAMON kernel API users such as
DAMON_RECLAIM would need to do similar work.  To reduce unnecessary
future duplciated efforts, support multiple goals from DAMOS core layer.
To make the support in minimum non-destructive change, keep the old
single goal setup interface, and add multiple goals setup.  The single
goal will treated as one of the multiple goals, so old API users are not
required to make any change.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h | 17 ++++++++++
 mm/damon/core.c       | 78 +++++++++++++++++++++++++++++++++++++++----
 2 files changed, 88 insertions(+), 7 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 2fe345adf6b2..4bd898eaf80e 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -130,6 +130,7 @@ enum damos_action {
  * struct damos_quota_goal - DAMOS scheme quota auto-tuning goal.
  * @get_score:		Function for getting current score of the goal.
  * @get_score_arg:	Parameter for @get_score
+ * @list:		List head for siblings.
  *
  * Data structure for getting the current score of the quota tuning goal.
  * Calling @get_score with @get_score_arg as the parameter should return the
@@ -140,6 +141,7 @@ enum damos_action {
 struct damos_quota_goal {
 	unsigned long (*get_score)(void *arg);
 	void *get_score_arg;
+	struct list_head list;
 };
 
 /**
@@ -148,6 +150,7 @@ struct damos_quota_goal {
  * @ms:			Maximum milliseconds that the scheme can use.
  * @sz:			Maximum bytes of memory that the action can be applied.
  * @goal:		Quota auto-tuning goal.
+ * @goals:		Head of quota tuning goals (&damos_quota_goal) list.
  * @esz:		Effective size quota in bytes.
  *
  * @weight_sz:		Weight of the region's size for prioritization.
@@ -171,6 +174,8 @@ struct damos_quota_goal {
  * every @reset_interval.  Then, if the new size quota is smaller than the
  * effective quota, it uses the new size quota as the effective quota.
  *
+ * If @goals is not empty, same action is taken for each goal of the list.
+ *
  * The resulting effective size quota in bytes is set to @esz.
  *
  * For selecting regions within the quota, DAMON prioritizes current scheme's
@@ -184,6 +189,7 @@ struct damos_quota {
 	unsigned long ms;
 	unsigned long sz;
 	struct damos_quota_goal goal;
+	struct list_head goals;
 	unsigned long esz;
 
 	unsigned int weight_sz;
@@ -648,6 +654,12 @@ static inline unsigned long damon_sz_region(struct damon_region *r)
 #define damon_for_each_scheme_safe(s, next, ctx) \
 	list_for_each_entry_safe(s, next, &(ctx)->schemes, list)
 
+#define damos_for_each_quota_goal(goal, quota) \
+	list_for_each_entry(goal, &quota->goals, list)
+
+#define damos_for_each_quota_goal_safe(goal, next, quota) \
+	list_for_each_entry_safe(goal, next, &(quota)->goals, list)
+
 #define damos_for_each_filter(f, scheme) \
 	list_for_each_entry(f, &(scheme)->filters, list)
 
@@ -681,6 +693,11 @@ struct damos_filter *damos_new_filter(enum damos_filter_type type,
 void damos_add_filter(struct damos *s, struct damos_filter *f);
 void damos_destroy_filter(struct damos_filter *f);
 
+struct damos_quota_goal *damos_new_quota_goal(
+		unsigned long (*get_score)(void *), void *get_score_arg);
+void damos_add_quota_goal(struct damos_quota *q, struct damos_quota_goal *g);
+void damos_destroy_quota_goal(struct damos_quota_goal *goal);
+
 struct damos *damon_new_scheme(struct damos_access_pattern *pattern,
 			enum damos_action action,
 			unsigned long apply_interval_us,
diff --git a/mm/damon/core.c b/mm/damon/core.c
index fe4209672121..b6cd99b64e85 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -299,6 +299,41 @@ void damos_destroy_filter(struct damos_filter *f)
 	damos_free_filter(f);
 }
 
+struct damos_quota_goal *damos_new_quota_goal(
+		unsigned long (*get_score)(void *), void *get_score_arg)
+{
+	struct damos_quota_goal *goal;
+
+	goal = kmalloc(sizeof(*goal), GFP_KERNEL);
+	if (!goal)
+		return NULL;
+	goal->get_score = get_score;
+	goal->get_score_arg = get_score_arg;
+	INIT_LIST_HEAD(&goal->list);
+	return goal;
+}
+
+void damos_add_quota_goal(struct damos_quota *q, struct damos_quota_goal *g)
+{
+	list_add_tail(&g->list, &q->goals);
+}
+
+static void damos_del_quota_goal(struct damos_quota_goal *g)
+{
+	list_del(&g->list);
+}
+
+static void damos_free_quota_goal(struct damos_quota_goal *g)
+{
+	kfree(g);
+}
+
+void damos_destroy_quota_goal(struct damos_quota_goal *g)
+{
+	damos_del_quota_goal(g);
+	damos_free_quota_goal(g);
+}
+
 /* initialize fields of @quota that normally API users wouldn't set */
 static struct damos_quota *damos_quota_init(struct damos_quota *quota)
 {
@@ -337,6 +372,8 @@ struct damos *damon_new_scheme(struct damos_access_pattern *pattern,
 	INIT_LIST_HEAD(&scheme->list);
 
 	scheme->quota = *(damos_quota_init(quota));
+	/* quota.goals should be separately set by caller */
+	INIT_LIST_HEAD(&scheme->quota.goals);
 
 	scheme->wmarks = *wmarks;
 	scheme->wmarks.activated = true;
@@ -373,8 +410,12 @@ static void damon_free_scheme(struct damos *s)
 
 void damon_destroy_scheme(struct damos *s)
 {
+	struct damos_quota_goal *g, *g_next;
 	struct damos_filter *f, *next;
 
+	damos_for_each_quota_goal_safe(g, g_next, &s->quota)
+		damos_destroy_quota_goal(g);
+
 	damos_for_each_filter_safe(f, next, s)
 		damos_destroy_filter(f);
 	damon_del_scheme(s);
@@ -1083,22 +1124,44 @@ static unsigned long damon_feed_loop_next_input(unsigned long last_input,
 	return min_input;
 }
 
-/* Called only if quota->ms, quota->sz, or quota->goal.get_score are set */
+/* Return the highest score since it makes schemes least aggressive */
+static unsigned long damos_quota_score(struct damos_quota *quota)
+{
+	struct damos_quota_goal *goal;
+	unsigned long highest_score = 0;
+
+	if (quota->goal.get_score)
+		highest_score = quota->goal.get_score(
+				quota->goal.get_score_arg);
+
+	damos_for_each_quota_goal(goal, quota)
+		highest_score = max(highest_score,
+				goal->get_score(goal->get_score_arg));
+
+	return highest_score;
+}
+
+/*
+ * Called only if quota->ms, quota->sz, or quota->goal.get_score are set, or
+ * quota->goals is not empty
+ */
 static void damos_set_effective_quota(struct damos_quota *quota)
 {
 	unsigned long throughput;
 	unsigned long esz;
 
-	if (!quota->ms && !quota->goal.get_score) {
+	if (!quota->ms && !quota->goal.get_score &&
+			list_empty(&quota->goals)) {
 		quota->esz = quota->sz;
 		return;
 	}
 
-	if (quota->goal.get_score) {
+	if (quota->goal.get_score || !list_empty(&quota->goals)) {
+		unsigned long score = damos_quota_score(quota);
+
 		quota->esz_bp = damon_feed_loop_next_input(
 				max(quota->esz_bp, 10000UL),
-				quota->goal.get_score(
-					quota->goal.get_score_arg));
+				score);
 		esz = quota->esz_bp / 10000;
 	}
 
@@ -1108,7 +1171,7 @@ static void damos_set_effective_quota(struct damos_quota *quota)
 				quota->total_charged_ns;
 		else
 			throughput = PAGE_SIZE * 1024;
-		if (quota->goal.get_score)
+		if (quota->goal.get_score || !list_empty(&quota->goals))
 			esz = min(throughput * quota->ms, esz);
 		else
 			esz = throughput * quota->ms;
@@ -1128,7 +1191,8 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s)
 	unsigned long cumulated_sz;
 	unsigned int score, max_score = 0;
 
-	if (!quota->ms && !quota->sz && !quota->goal.get_score)
+	if (!quota->ms && !quota->sz && !quota->goal.get_score &&
+			list_empty(&quota->goals))
 		return;
 
 	/* New charge window starts */
-- 
2.39.2

[PATCH 09/20] mm/damon/sysfs: use only quota->goals

[SeongJae Park]

DAMON sysfs interface implements multiple quota auto-tuning goals on its
level since the DAMOS core logic was supporting only single goal.  Now
the core logic supports multiple goals on its level.  Update DAMON sysfs
interface to reuse the core logic and drop unnecessary duplicated
multiple goals implementation.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-common.h  |  2 +-
 mm/damon/sysfs-schemes.c | 49 +++++++++++++++++++++++++++-------------
 mm/damon/sysfs.c         |  3 +--
 3 files changed, 35 insertions(+), 19 deletions(-)

diff --git a/mm/damon/sysfs-common.h b/mm/damon/sysfs-common.h
index 5a1ac15fb2f8..a63f51577cff 100644
--- a/mm/damon/sysfs-common.h
+++ b/mm/damon/sysfs-common.h
@@ -59,7 +59,7 @@ int damon_sysfs_schemes_clear_regions(
 		struct damon_sysfs_schemes *sysfs_schemes,
 		struct damon_ctx *ctx);
 
-void damos_sysfs_set_quota_scores(struct damon_sysfs_schemes *sysfs_schemes,
+int damos_sysfs_set_quota_scores(struct damon_sysfs_schemes *sysfs_schemes,
 		struct damon_ctx *ctx);
 
 void damos_sysfs_update_effective_quotas(
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 85ef58f98a87..7bf94b1ed6f7 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1887,30 +1887,34 @@ static unsigned long damos_sysfs_get_quota_score(void *arg)
 	return (unsigned long)arg;
 }
 
-static void damos_sysfs_set_quota_score(
+static int damos_sysfs_set_quota_score(
 		struct damos_sysfs_quota_goals *sysfs_goals,
 		struct damos_quota *quota)
 {
-	struct damos_sysfs_quota_goal *sysfs_goal;
+	struct damos_quota_goal *goal, *next;
 	int i;
 
-	quota->goal.get_score = NULL;
-	quota->goal.get_score_arg = (void *)0;
+	damos_for_each_quota_goal_safe(goal, next, quota)
+		damos_destroy_quota_goal(goal);
+
 	for (i = 0; i < sysfs_goals->nr; i++) {
-		sysfs_goal = sysfs_goals->goals_arr[i];
+		struct damos_sysfs_quota_goal *sysfs_goal =
+			sysfs_goals->goals_arr[i];
+
 		if (!sysfs_goal->target_value)
 			continue;
 
-		/* Higher score makes scheme less aggressive */
-		quota->goal.get_score_arg = (void *)max(
-				(unsigned long)quota->goal.get_score_arg,
-				sysfs_goal->current_value * 10000 /
-				sysfs_goal->target_value);
-		quota->goal.get_score = damos_sysfs_get_quota_score;
+		goal = damos_new_quota_goal(damos_sysfs_get_quota_score,
+				(void *)(sysfs_goal->current_value * 10000 /
+				sysfs_goal->target_value));
+		if (!goal)
+			return -ENOMEM;
+		damos_add_quota_goal(quota, goal);
 	}
+	return 0;
 }
 
-void damos_sysfs_set_quota_scores(struct damon_sysfs_schemes *sysfs_schemes,
+int damos_sysfs_set_quota_scores(struct damon_sysfs_schemes *sysfs_schemes,
 		struct damon_ctx *ctx)
 {
 	struct damos *scheme;
@@ -1918,16 +1922,21 @@ void damos_sysfs_set_quota_scores(struct damon_sysfs_schemes *sysfs_schemes,
 
 	damon_for_each_scheme(scheme, ctx) {
 		struct damon_sysfs_scheme *sysfs_scheme;
+		int err;
 
 		/* user could have removed the scheme sysfs dir */
 		if (i >= sysfs_schemes->nr)
 			break;
 
 		sysfs_scheme = sysfs_schemes->schemes_arr[i];
-		damos_sysfs_set_quota_score(sysfs_scheme->quotas->goals,
+		err = damos_sysfs_set_quota_score(sysfs_scheme->quotas->goals,
 				&scheme->quota);
+		if (err)
+			/* kdamond will clean up schemes and terminated */
+			return err;
 		i++;
 	}
+	return 0;
 }
 
 void damos_sysfs_update_effective_quotas(
@@ -1987,13 +1996,17 @@ static struct damos *damon_sysfs_mk_scheme(
 		.low = sysfs_wmarks->low,
 	};
 
-	damos_sysfs_set_quota_score(sysfs_quotas->goals, &quota);
-
 	scheme = damon_new_scheme(&pattern, sysfs_scheme->action,
 			sysfs_scheme->apply_interval_us, &quota, &wmarks);
 	if (!scheme)
 		return NULL;
 
+	err = damos_sysfs_set_quota_score(sysfs_quotas->goals, &scheme->quota);
+	if (err) {
+		damon_destroy_scheme(scheme);
+		return NULL;
+	}
+
 	err = damon_sysfs_set_scheme_filters(scheme, sysfs_filters);
 	if (err) {
 		damon_destroy_scheme(scheme);
@@ -2029,7 +2042,11 @@ static void damon_sysfs_update_scheme(struct damos *scheme,
 	scheme->quota.weight_nr_accesses = sysfs_weights->nr_accesses;
 	scheme->quota.weight_age = sysfs_weights->age;
 
-	damos_sysfs_set_quota_score(sysfs_quotas->goals, &scheme->quota);
+	err = damos_sysfs_set_quota_score(sysfs_quotas->goals, &scheme->quota);
+	if (err) {
+		damon_destroy_scheme(scheme);
+		return;
+	}
 
 	scheme->wmarks.metric = sysfs_wmarks->metric;
 	scheme->wmarks.interval = sysfs_wmarks->interval_us;
diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index cc2d88a901f4..6fee383bc0c5 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -1377,8 +1377,7 @@ static int damon_sysfs_commit_schemes_quota_goals(
 
 	ctx = sysfs_kdamond->damon_ctx;
 	sysfs_ctx = sysfs_kdamond->contexts->contexts_arr[0];
-	damos_sysfs_set_quota_scores(sysfs_ctx->schemes, ctx);
-	return 0;
+	return damos_sysfs_set_quota_scores(sysfs_ctx->schemes, ctx);
 }
 
 /*
-- 
2.39.2

[PATCH 10/20] mm/damon/core: remove ->goal field of damos_quota

[SeongJae Park]

DAMOS quota auto-tuning feature supports static signle goal and dynamic
multiple goals via DAMON kernel API, specifically via ->goal and ->goals
fields of damos_quota struct, respectively.  All in-tree DAMOS kernel
API users are using only the dynamic multiple goals now.  Remove the
unsued static single goal interface.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h | 12 ++++--------
 mm/damon/core.c       | 17 +++++------------
 2 files changed, 9 insertions(+), 20 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 4bd898eaf80e..76c965c1eea3 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -149,7 +149,6 @@ struct damos_quota_goal {
  * @reset_interval:	Charge reset interval in milliseconds.
  * @ms:			Maximum milliseconds that the scheme can use.
  * @sz:			Maximum bytes of memory that the action can be applied.
- * @goal:		Quota auto-tuning goal.
  * @goals:		Head of quota tuning goals (&damos_quota_goal) list.
  * @esz:		Effective size quota in bytes.
  *
@@ -169,12 +168,10 @@ struct damos_quota_goal {
  * throughput of the scheme's action.  DAMON then compares it against &sz and
  * uses smaller one as the effective quota.
  *
- * If ->get_score field of @goal is set, DAMON calculates yet another size
- * quota based on the goal using its internal feedback loop algorithm, for
- * every @reset_interval.  Then, if the new size quota is smaller than the
- * effective quota, it uses the new size quota as the effective quota.
- *
- * If @goals is not empty, same action is taken for each goal of the list.
+ * If @goals is not empt, DAMON calculates yet another size quota based on the
+ * goals using its internal feedback loop algorithm, for every @reset_interval.
+ * Then, if the new size quota is smaller than the effective quota, it uses the
+ * new size quota as the effective quota.
  *
  * The resulting effective size quota in bytes is set to @esz.
  *
@@ -188,7 +185,6 @@ struct damos_quota {
 	unsigned long reset_interval;
 	unsigned long ms;
 	unsigned long sz;
-	struct damos_quota_goal goal;
 	struct list_head goals;
 	unsigned long esz;
 
diff --git a/mm/damon/core.c b/mm/damon/core.c
index b6cd99b64e85..7b06d926c552 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1130,10 +1130,6 @@ static unsigned long damos_quota_score(struct damos_quota *quota)
 	struct damos_quota_goal *goal;
 	unsigned long highest_score = 0;
 
-	if (quota->goal.get_score)
-		highest_score = quota->goal.get_score(
-				quota->goal.get_score_arg);
-
 	damos_for_each_quota_goal(goal, quota)
 		highest_score = max(highest_score,
 				goal->get_score(goal->get_score_arg));
@@ -1142,21 +1138,19 @@ static unsigned long damos_quota_score(struct damos_quota *quota)
 }
 
 /*
- * Called only if quota->ms, quota->sz, or quota->goal.get_score are set, or
- * quota->goals is not empty
+ * Called only if quota->ms, or quota->sz are set, or quota->goals is not empty
  */
 static void damos_set_effective_quota(struct damos_quota *quota)
 {
 	unsigned long throughput;
 	unsigned long esz;
 
-	if (!quota->ms && !quota->goal.get_score &&
-			list_empty(&quota->goals)) {
+	if (!quota->ms && list_empty(&quota->goals)) {
 		quota->esz = quota->sz;
 		return;
 	}
 
-	if (quota->goal.get_score || !list_empty(&quota->goals)) {
+	if (!list_empty(&quota->goals)) {
 		unsigned long score = damos_quota_score(quota);
 
 		quota->esz_bp = damon_feed_loop_next_input(
@@ -1171,7 +1165,7 @@ static void damos_set_effective_quota(struct damos_quota *quota)
 				quota->total_charged_ns;
 		else
 			throughput = PAGE_SIZE * 1024;
-		if (quota->goal.get_score || !list_empty(&quota->goals))
+		if (!list_empty(&quota->goals))
 			esz = min(throughput * quota->ms, esz);
 		else
 			esz = throughput * quota->ms;
@@ -1191,8 +1185,7 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s)
 	unsigned long cumulated_sz;
 	unsigned int score, max_score = 0;
 
-	if (!quota->ms && !quota->sz && !quota->goal.get_score &&
-			list_empty(&quota->goals))
+	if (!quota->ms && !quota->sz && list_empty(&quota->goals))
 		return;
 
 	/* New charge window starts */
-- 
2.39.2

[PATCH 11/20] mm/damon/core: let goal specified with only target and current values

[SeongJae Park]

DAMOS quota auto-tuning feature let users to set the goal by providing a
function for getting the current score of the tuned quota.  It allows
flexible goal setup, but only simple user-set quota is currently being
used.  As a result, the only user of the DAMOS quota auto-tuning is
using a silly void pointer casting based score value passing function.
Simplify the interface and the user code by letting user directly set
the target and the current value.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h    | 19 +++++++++----------
 mm/damon/core.c          |  9 +++++----
 mm/damon/sysfs-schemes.c | 10 ++--------
 3 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 76c965c1eea3..de0cdc7f96d2 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -128,19 +128,18 @@ enum damos_action {
 
 /**
  * struct damos_quota_goal - DAMOS scheme quota auto-tuning goal.
- * @get_score:		Function for getting current score of the goal.
- * @get_score_arg:	Parameter for @get_score
+ * @target_value:	Target value to achieve with the tuning.
+ * @current_value:	Current value that achieving with the tuning.
  * @list:		List head for siblings.
  *
- * Data structure for getting the current score of the quota tuning goal.
- * Calling @get_score with @get_score_arg as the parameter should return the
- * current score.  Then the score is entered to DAMON's internal feedback loop
- * mechanism to get the auto-tuned quota.  The goal of the tuning is getting
- * the feedback score value of 10,000.
+ * Data structure for getting the current score of the quota tuning goal.  The
+ * score is calculated by how close @current_value and @target_value are.  Then
+ * the score is entered to DAMON's internal feedback loop mechanism to get the
+ * auto-tuned quota.
  */
 struct damos_quota_goal {
-	unsigned long (*get_score)(void *arg);
-	void *get_score_arg;
+	unsigned long target_value;
+	unsigned long current_value;
 	struct list_head list;
 };
 
@@ -690,7 +689,7 @@ void damos_add_filter(struct damos *s, struct damos_filter *f);
 void damos_destroy_filter(struct damos_filter *f);
 
 struct damos_quota_goal *damos_new_quota_goal(
-		unsigned long (*get_score)(void *), void *get_score_arg);
+		unsigned long target_value, unsigned long current_value);
 void damos_add_quota_goal(struct damos_quota *q, struct damos_quota_goal *g);
 void damos_destroy_quota_goal(struct damos_quota_goal *goal);
 
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 7b06d926c552..907f467fc8c0 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -300,15 +300,15 @@ void damos_destroy_filter(struct damos_filter *f)
 }
 
 struct damos_quota_goal *damos_new_quota_goal(
-		unsigned long (*get_score)(void *), void *get_score_arg)
+		unsigned long target_value, unsigned long current_value)
 {
 	struct damos_quota_goal *goal;
 
 	goal = kmalloc(sizeof(*goal), GFP_KERNEL);
 	if (!goal)
 		return NULL;
-	goal->get_score = get_score;
-	goal->get_score_arg = get_score_arg;
+	goal->target_value = target_value;
+	goal->current_value = current_value;
 	INIT_LIST_HEAD(&goal->list);
 	return goal;
 }
@@ -1132,7 +1132,8 @@ static unsigned long damos_quota_score(struct damos_quota *quota)
 
 	damos_for_each_quota_goal(goal, quota)
 		highest_score = max(highest_score,
-				goal->get_score(goal->get_score_arg));
+				goal->current_value * 10000 /
+				goal->target_value);
 
 	return highest_score;
 }
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 7bf94b1ed6f7..50218a7bfa0a 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1882,11 +1882,6 @@ static int damon_sysfs_set_scheme_filters(struct damos *scheme,
 	return 0;
 }
 
-static unsigned long damos_sysfs_get_quota_score(void *arg)
-{
-	return (unsigned long)arg;
-}
-
 static int damos_sysfs_set_quota_score(
 		struct damos_sysfs_quota_goals *sysfs_goals,
 		struct damos_quota *quota)
@@ -1904,9 +1899,8 @@ static int damos_sysfs_set_quota_score(
 		if (!sysfs_goal->target_value)
 			continue;
 
-		goal = damos_new_quota_goal(damos_sysfs_get_quota_score,
-				(void *)(sysfs_goal->current_value * 10000 /
-				sysfs_goal->target_value));
+		goal = damos_new_quota_goal(sysfs_goal->target_value,
+				sysfs_goal->current_value);
 		if (!goal)
 			return -ENOMEM;
 		damos_add_quota_goal(quota, goal);
-- 
2.39.2

[PATCH 12/20] mm/damon/core: support multiple metrics for quota goal

[SeongJae Park]

DAMOS quota auto-tuning asks users to assess the current tuned quota and
provide the feedback in a manual and repeated way.  It allows users
generate the feedback from a source that the kernel cannot access, and
writing a script or a function for doing the manual and repeated feeding
is not a big deal.  However, additional works are additional works, and
it could be more efficient if DAMOS could do the fetch itself,
especially in case of DAMON sysfs interface use case, since it can avoid
the context switches between the user-space and the kernel-space, though
the overhead would be only trivial in most cases.  Also in many cases,
feedbacks could be made from kernel-accessible sources, such as PSI, CPU
usage, etc.  Make the quota goal to support multiple types of metrics
including such ones.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h    | 26 +++++++++++++++++++++++---
 mm/damon/core.c          | 22 +++++++++++++++++++---
 mm/damon/sysfs-schemes.c |  5 +++--
 3 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index de0cdc7f96d2..5a06993d8479 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -126,18 +126,37 @@ enum damos_action {
 	NR_DAMOS_ACTIONS,
 };
 
+/**
+ * enum damos_quota_goal_metric - Represents the metric to be used as the goal
+ *
+ * @DAMOS_QUOTA_USER_INPUT:	User-input value.
+ * @NR_DAMOS_QUOTA_GOAL_METRICS:	Number of DAMOS quota goal metrics.
+ *
+ * Metrics equal to larger than @NR_DAMOS_QUOTA_GOAL_METRICS are unsupported.
+ */
+enum damos_quota_goal_metric {
+	DAMOS_QUOTA_USER_INPUT,
+	NR_DAMOS_QUOTA_GOAL_METRICS,
+};
+
 /**
  * struct damos_quota_goal - DAMOS scheme quota auto-tuning goal.
- * @target_value:	Target value to achieve with the tuning.
- * @current_value:	Current value that achieving with the tuning.
+ * @metric:		Metric to be used for representing the goal.
+ * @target_value:	Target value of @metric to achieve with the tuning.
+ * @current_value:	Current value of @metric.
  * @list:		List head for siblings.
  *
  * Data structure for getting the current score of the quota tuning goal.  The
  * score is calculated by how close @current_value and @target_value are.  Then
  * the score is entered to DAMON's internal feedback loop mechanism to get the
  * auto-tuned quota.
+ *
+ * If @metric is DAMOS_QUOTA_USER_INPUT, @current_value should be manually
+ * entered by the user, probably inside the kdamond callbacks.  Otherwise,
+ * DAMON sets @current_value with self-measured value of @metric.
  */
 struct damos_quota_goal {
+	enum damos_quota_goal_metric metric;
 	unsigned long target_value;
 	unsigned long current_value;
 	struct list_head list;
@@ -689,7 +708,8 @@ void damos_add_filter(struct damos *s, struct damos_filter *f);
 void damos_destroy_filter(struct damos_filter *f);
 
 struct damos_quota_goal *damos_new_quota_goal(
-		unsigned long target_value, unsigned long current_value);
+		enum damos_quota_goal_metric metric,
+		unsigned long target_value);
 void damos_add_quota_goal(struct damos_quota *q, struct damos_quota_goal *g);
 void damos_destroy_quota_goal(struct damos_quota_goal *goal);
 
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 907f467fc8c0..973423166ee2 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -300,15 +300,16 @@ void damos_destroy_filter(struct damos_filter *f)
 }
 
 struct damos_quota_goal *damos_new_quota_goal(
-		unsigned long target_value, unsigned long current_value)
+		enum damos_quota_goal_metric metric,
+		unsigned long target_value)
 {
 	struct damos_quota_goal *goal;
 
 	goal = kmalloc(sizeof(*goal), GFP_KERNEL);
 	if (!goal)
 		return NULL;
+	goal->metric = metric;
 	goal->target_value = target_value;
-	goal->current_value = current_value;
 	INIT_LIST_HEAD(&goal->list);
 	return goal;
 }
@@ -1124,16 +1125,31 @@ static unsigned long damon_feed_loop_next_input(unsigned long last_input,
 	return min_input;
 }
 
+static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal)
+{
+	u64 now_psi_total;
+
+	switch (goal->metric) {
+	case DAMOS_QUOTA_USER_INPUT:
+		/* User should already set goal->current_value */
+		break;
+	default:
+		break;
+	}
+}
+
 /* Return the highest score since it makes schemes least aggressive */
 static unsigned long damos_quota_score(struct damos_quota *quota)
 {
 	struct damos_quota_goal *goal;
 	unsigned long highest_score = 0;
 
-	damos_for_each_quota_goal(goal, quota)
+	damos_for_each_quota_goal(goal, quota) {
+		damos_set_quota_goal_current_value(goal);
 		highest_score = max(highest_score,
 				goal->current_value * 10000 /
 				goal->target_value);
+	}
 
 	return highest_score;
 }
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 50218a7bfa0a..7a8a39f2679b 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1899,10 +1899,11 @@ static int damos_sysfs_set_quota_score(
 		if (!sysfs_goal->target_value)
 			continue;
 
-		goal = damos_new_quota_goal(sysfs_goal->target_value,
-				sysfs_goal->current_value);
+		goal = damos_new_quota_goal(DAMOS_QUOTA_USER_INPUT,
+				sysfs_goal->target_value);
 		if (!goal)
 			return -ENOMEM;
+		goal->current_value = sysfs_goal->current_value;
 		damos_add_quota_goal(quota, goal);
 	}
 	return 0;
-- 
2.39.2

[PATCH 13/20] mm/damon/core: implement PSI metric DAMOS quota goal

[SeongJae Park]

Extend DAMOS quota goal metric with system wide memory pressure stall
time.  Specifically, the system level 'some' PSI for memory is used.
The target value can be set in microseconds.  DAMOS measures the
increased amount of the PSI metric in last quota_reset_interval and use
the ratio of it versus the user-specified target PSI value as the score
for the auto-tuning feedback loop.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h |  7 +++++++
 mm/damon/core.c       | 25 +++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 5a06993d8479..886d07294f4e 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -130,12 +130,14 @@ enum damos_action {
  * enum damos_quota_goal_metric - Represents the metric to be used as the goal
  *
  * @DAMOS_QUOTA_USER_INPUT:	User-input value.
+ * @DAMOS_QUOTA_SOME_MEM_PSI_US:	System level some memory PSI in us.
  * @NR_DAMOS_QUOTA_GOAL_METRICS:	Number of DAMOS quota goal metrics.
  *
  * Metrics equal to larger than @NR_DAMOS_QUOTA_GOAL_METRICS are unsupported.
  */
 enum damos_quota_goal_metric {
 	DAMOS_QUOTA_USER_INPUT,
+	DAMOS_QUOTA_SOME_MEM_PSI_US,
 	NR_DAMOS_QUOTA_GOAL_METRICS,
 };
 
@@ -144,6 +146,7 @@ enum damos_quota_goal_metric {
  * @metric:		Metric to be used for representing the goal.
  * @target_value:	Target value of @metric to achieve with the tuning.
  * @current_value:	Current value of @metric.
+ * @last_psi_total:	Last measured total PSI
  * @list:		List head for siblings.
  *
  * Data structure for getting the current score of the quota tuning goal.  The
@@ -159,6 +162,10 @@ struct damos_quota_goal {
 	enum damos_quota_goal_metric metric;
 	unsigned long target_value;
 	unsigned long current_value;
+	/* metric-dependent fields */
+	union {
+		u64 last_psi_total;
+	};
 	struct list_head list;
 };
 
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 973423166ee2..6d503c1c125e 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -11,6 +11,7 @@
 #include <linux/delay.h>
 #include <linux/kthread.h>
 #include <linux/mm.h>
+#include <linux/psi.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 
@@ -1125,6 +1126,25 @@ static unsigned long damon_feed_loop_next_input(unsigned long last_input,
 	return min_input;
 }
 
+#ifdef CONFIG_PSI
+
+static u64 damos_get_some_mem_psi_total(void)
+{
+	if (static_branch_likely(&psi_disabled))
+		return 0;
+	return div_u64(psi_system.total[PSI_AVGS][PSI_MEM * 2],
+			NSEC_PER_USEC);
+}
+
+#else	/* CONFIG_PSI */
+
+static inline u64 damos_get_some_mem_psi_total(void)
+{
+	return 0;
+};
+
+#endif	/* CONFIG_PSI */
+
 static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal)
 {
 	u64 now_psi_total;
@@ -1133,6 +1153,11 @@ static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal)
 	case DAMOS_QUOTA_USER_INPUT:
 		/* User should already set goal->current_value */
 		break;
+	case DAMOS_QUOTA_SOME_MEM_PSI_US:
+		now_psi_total = damos_get_some_mem_psi_total();
+		goal->current_value = now_psi_total - goal->last_psi_total;
+		goal->last_psi_total = now_psi_total;
+		break;
 	default:
 		break;
 	}
-- 
2.39.2

[PATCH 14/20] mm/damon/sysfs-schemes: support PSI-based quota auto-tune

[SeongJae Park]

Extend DAMON sysfs interface to support the PSI-based quota auto-tuning
by adding a new file, 'target_metric' under the quota goal directory.
Old users don't get any behavioral changes since the default value of
the metric is 'user input'.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-schemes.c | 42 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 40 insertions(+), 2 deletions(-)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 7a8a39f2679b..53a90ac678fb 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -826,15 +826,48 @@ static const struct kobj_type damon_sysfs_watermarks_ktype = {
 
 struct damos_sysfs_quota_goal {
 	struct kobject kobj;
+	enum damos_quota_goal_metric metric;
 	unsigned long target_value;
 	unsigned long current_value;
 };
 
+/* This should match with enum damos_action */
+static const char * const damos_sysfs_quota_goal_metric_strs[] = {
+	"user_input",
+	"some_mem_psi_us",
+};
+
 static struct damos_sysfs_quota_goal *damos_sysfs_quota_goal_alloc(void)
 {
 	return kzalloc(sizeof(struct damos_sysfs_quota_goal), GFP_KERNEL);
 }
 
+static ssize_t target_metric_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damos_sysfs_quota_goal *goal = container_of(kobj,
+			struct damos_sysfs_quota_goal, kobj);
+
+	return sysfs_emit(buf, "%s\n",
+			damos_sysfs_quota_goal_metric_strs[goal->metric]);
+}
+
+static ssize_t target_metric_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damos_sysfs_quota_goal *goal = container_of(kobj,
+			struct damos_sysfs_quota_goal, kobj);
+	enum damos_quota_goal_metric m;
+
+	for (m = 0; m < NR_DAMOS_QUOTA_GOAL_METRICS; m++) {
+		if (sysfs_streq(buf, damos_sysfs_quota_goal_metric_strs[m])) {
+			goal->metric = m;
+			return count;
+		}
+	}
+	return -EINVAL;
+}
+
 static ssize_t target_value_show(struct kobject *kobj,
 		struct kobj_attribute *attr, char *buf)
 {
@@ -880,6 +913,9 @@ static void damos_sysfs_quota_goal_release(struct kobject *kobj)
 	kfree(container_of(kobj, struct damos_sysfs_quota_goal, kobj));
 }
 
+static struct kobj_attribute damos_sysfs_quota_goal_target_metric_attr =
+		__ATTR_RW_MODE(target_metric, 0600);
+
 static struct kobj_attribute damos_sysfs_quota_goal_target_value_attr =
 		__ATTR_RW_MODE(target_value, 0600);
 
@@ -887,6 +923,7 @@ static struct kobj_attribute damos_sysfs_quota_goal_current_value_attr =
 		__ATTR_RW_MODE(current_value, 0600);
 
 static struct attribute *damos_sysfs_quota_goal_attrs[] = {
+	&damos_sysfs_quota_goal_target_metric_attr.attr,
 	&damos_sysfs_quota_goal_target_value_attr.attr,
 	&damos_sysfs_quota_goal_current_value_attr.attr,
 	NULL,
@@ -1899,11 +1936,12 @@ static int damos_sysfs_set_quota_score(
 		if (!sysfs_goal->target_value)
 			continue;
 
-		goal = damos_new_quota_goal(DAMOS_QUOTA_USER_INPUT,
+		goal = damos_new_quota_goal(sysfs_goal->metric,
 				sysfs_goal->target_value);
 		if (!goal)
 			return -ENOMEM;
-		goal->current_value = sysfs_goal->current_value;
+		if (sysfs_goal->metric == DAMOS_QUOTA_USER_INPUT)
+			goal->current_value = sysfs_goal->current_value;
 		damos_add_quota_goal(quota, goal);
 	}
 	return 0;
-- 
2.39.2

[PATCH 15/20] Docs/mm/damon/design: document quota goal self-tuning

[SeongJae Park]

update DAMON design doc to explain the quota goal self-tuning, which can
be used by setting the goal's metric to metrics that kernel can
self-retrieve.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 2bd0c203dcfb..8c89d26f0baa 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -398,12 +398,28 @@ Aim-oriented Feedback-driven Auto-tuning
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Automatic feedback-driven quota tuning.  Instead of setting the absolute quota
-value, users can repeatedly provide numbers representing how much of their goal
-for the scheme is achieved as feedback.  DAMOS then automatically tunes the
+value, users can specify the metric of their interest, and what target value
+they want the metric value to be.  DAMOS then automatically tunes the
 aggressiveness (the quota) of the corresponding scheme.  For example, if DAMOS
 is under achieving the goal, DAMOS automatically increases the quota.  If DAMOS
 is over achieving the goal, it decreases the quota.
 
+The goal can be specified with three parameters, namely ``target_metric``,
+``target_value``, and ``current_value``.  The auto-tuning mechanism tries to
+make ``current_value`` of ``target_metric`` be same to ``target_value``.
+Currently, two ``target_metric`` are provided.
+
+- ``user_input``: User-provided value.  Users could use any metric that they
+  has interest in for the value.  Use space main workload's latency or
+  throughput, system metrics like free memory ratio or memory pressure stall
+  time (PSI) could be examples.  Note that users should explicitly set
+  ``current_value`` on their own in this case.  In other words, users should
+  repeatedly provide the feedback.
+- ``some_mem_psi_us``: System-wide ``some`` memory pressure stall information
+  in microseconds that measured from last quota reset to next quota reset.
+  DAMOS does the measurement on its own, so only ``target_value`` need to be
+  set by users at the initial time.  In other words, DAMOS does self-feedback.
+
 
 .. _damon_design_damos_watermarks:
 
-- 
2.39.2

[PATCH 16/20] Docs/ABI/damon: document quota goal metric file

[SeongJae Park]

Update DAMON ABI document for the quota goal target_metric file.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/ABI/testing/sysfs-kernel-mm-damon | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-damon b/Documentation/ABI/testing/sysfs-kernel-mm-damon
index a1e4fdb04f95..dad4d5ffd786 100644
--- a/Documentation/ABI/testing/sysfs-kernel-mm-damon
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-damon
@@ -229,6 +229,12 @@ Description:	Writing a number 'N' to this file creates the number of
 		directories for setting automatic tuning of the scheme's
 		aggressiveness named '0' to 'N-1' under the goals/ directory.
 
+What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/quotas/goals/<G>/target_metric
+Date:		Feb 2024
+Contact:	SeongJae Park <sj@kernel.org>
+Description:	Writing to and reading from this file sets and gets the quota
+		auto-tuning goal metric.
+
 What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/quotas/goals/<G>/target_value
 Date:		Nov 2023
 Contact:	SeongJae Park <sj@kernel.org>
-- 
2.39.2

[PATCH 17/20] Docs/admin-guide/mm/damon/usage: document quota goal metric file

[SeongJae Park]

Update DAMON usage document for the quota goal target_metric file.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/usage.rst | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index 220ebbde7324..b33eecfd0e90 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -86,7 +86,7 @@ comma (",").
     │ │ │ │ │ │ │ :ref:`quotas <sysfs_quotas>`/ms,bytes,reset_interval_ms,effective_bytes
     │ │ │ │ │ │ │ │ weights/sz_permil,nr_accesses_permil,age_permil
     │ │ │ │ │ │ │ │ :ref:`goals <sysfs_schemes_quota_goals>`/nr_goals
-    │ │ │ │ │ │ │ │ │ 0/target_value,current_value
+    │ │ │ │ │ │ │ │ │ 0/target_metric,target_value,current_value
     │ │ │ │ │ │ │ :ref:`watermarks <sysfs_watermarks>`/metric,interval_us,high,mid,low
     │ │ │ │ │ │ │ :ref:`filters <sysfs_filters>`/nr_filters
     │ │ │ │ │ │ │ │ 0/type,matching,memcg_id
@@ -366,11 +366,11 @@ number (``N``) to the file creates the number of child directories named ``0``
 to ``N-1``.  Each directory represents each goal and current achievement.
 Among the multiple feedback, the best one is used.
 
-Each goal directory contains two files, namely ``target_value`` and
-``current_value``.  Users can set and get any number to those files to set the
-feedback.  User space main workload's latency or throughput, system metrics
-like free memory ratio or memory pressure stall time (PSI) could be example
-metrics for the values.  Note that users should write
+Each goal directory contains three files, namely ``target_metric``,
+``target_value`` and ``current_value``.  Users can set and get the three
+parameters for the quota auto-tuning goals that specified on the :ref:`design
+doc <damon_design_damos_quota_auto_tuning>` by writing to and reading from each
+of the files.  Note that users should further write
 ``commit_schemes_quota_goals`` to the ``state`` file of the :ref:`kdamond
 directory <sysfs_kdamond>` to pass the feedback to DAMON.
 
-- 
2.39.2

[PATCH 18/20] mm/damon/reclaim: implement user-feedback driven quota auto-tuning

[SeongJae Park]

DAMOS supports user-feedback driven quota auto-tuning, but only DAMON
sysfs interface is using it.  Add support of the feature on
DAMON_RECLAIM by adding one more input parameter, namely
'quota_autotune_feedback', for providing the user feedback to
DAMON_RECLAIM.  It assumes the target value of the feedback is 10,000.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/reclaim.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index 66e190f0374a..9df6b8819998 100644
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -62,6 +62,21 @@ static struct damos_quota damon_reclaim_quota = {
 };
 DEFINE_DAMON_MODULES_DAMOS_QUOTAS(damon_reclaim_quota);
 
+/*
+ * User-specifiable feedback for auto-tuning of the effective quota.
+ *
+ * While keeping the caps that set by other quotas, DAMON_RECLAIM automatically
+ * increases and decreases the effective level of the quota aiming receiving this
+ * feedback of value ``10,000`` from the user.  DAMON_RECLAIM assumes the feedback
+ * value and the quota are positively proportional.  Value zero means disabling
+ * this auto-tuning feature.
+ *
+ * Disabled by default.
+ *
+ */
+static unsigned long quota_autotune_feedback __read_mostly;
+module_param(quota_autotune_feedback, ulong, 0600);
+
 static struct damos_watermarks damon_reclaim_wmarks = {
 	.metric = DAMOS_WMARK_FREE_MEM_RATE,
 	.interval = 5000000,	/* 5 seconds */
@@ -159,11 +174,13 @@ static void damon_reclaim_copy_quota_status(struct damos_quota *dst,
 	dst->charged_from = src->charged_from;
 	dst->charge_target_from = src->charge_target_from;
 	dst->charge_addr_from = src->charge_addr_from;
+	dst->esz_bp = src->esz_bp;
 }
 
 static int damon_reclaim_apply_parameters(void)
 {
 	struct damos *scheme, *old_scheme;
+	struct damos_quota_goal *goal;
 	struct damos_filter *filter;
 	int err = 0;
 
@@ -180,6 +197,17 @@ static int damon_reclaim_apply_parameters(void)
 			damon_reclaim_copy_quota_status(&scheme->quota,
 					&old_scheme->quota);
 	}
+
+	if (quota_autotune_feedback) {
+		goal = damos_new_quota_goal(DAMOS_QUOTA_USER_INPUT, 10000);
+		if (!goal) {
+			damon_destroy_scheme(scheme);
+			return -ENOMEM;
+		}
+		goal->current_value = quota_autotune_feedback;
+		damos_add_quota_goal(&scheme->quota, goal);
+	}
+
 	if (skip_anon) {
 		filter = damos_new_filter(DAMOS_FILTER_TYPE_ANON, true);
 		if (!filter) {
-- 
2.39.2

[PATCH 19/20] mm/damon/reclaim: implement memory PSI-driven quota self-tuning

[SeongJae Park]

Support the PSI-driven quota self-tuning from DAMON_RECLAIM by
introducing yet another parameter, 'quota_mem_pressure_us'.  Users can
set the desired amount of memory pressure stall time per each quota
reset interval using the parameter.  Then DAMON_RECLAIM monitor the
memory pressure stall time, specifically system-wide memory 'some' PSI
value that increased during the given time interval, and self-tune the
quota using the DAMOS core logic.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/reclaim.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index 9df6b8819998..9bd341d62b4c 100644
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -62,6 +62,21 @@ static struct damos_quota damon_reclaim_quota = {
 };
 DEFINE_DAMON_MODULES_DAMOS_QUOTAS(damon_reclaim_quota);
 
+/*
+ * 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.
+ *
+ * Disabled by default.
+ */
+static unsigned long quota_mem_pressure_us __read_mostly;
+module_param(quota_mem_pressure_us, ulong, 0600);
+
 /*
  * User-specifiable feedback for auto-tuning of the effective quota.
  *
@@ -198,6 +213,16 @@ static int damon_reclaim_apply_parameters(void)
 					&old_scheme->quota);
 	}
 
+	if (quota_mem_pressure_us) {
+		goal = damos_new_quota_goal(DAMOS_QUOTA_SOME_MEM_PSI_US,
+				quota_mem_pressure_us);
+		if (!goal) {
+			damon_destroy_scheme(scheme);
+			return -ENOMEM;
+		}
+		damos_add_quota_goal(&scheme->quota, goal);
+	}
+
 	if (quota_autotune_feedback) {
 		goal = damos_new_quota_goal(DAMOS_QUOTA_USER_INPUT, 10000);
 		if (!goal) {
-- 
2.39.2

[PATCH 20/20] Docs/admin-guide/mm/damon/reclaim: document auto-tuning parameters

[SeongJae Park]

Update DAMON_RECLAIM usage document for the user/self feedback based
auto-tuning of the quota.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 .../admin-guide/mm/damon/reclaim.rst          | 27 +++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/Documentation/admin-guide/mm/damon/reclaim.rst b/Documentation/admin-guide/mm/damon/reclaim.rst
index 343e25b252f4..af05ae617018 100644
--- a/Documentation/admin-guide/mm/damon/reclaim.rst
+++ b/Documentation/admin-guide/mm/damon/reclaim.rst
@@ -117,6 +117,33 @@ milliseconds.
 
 1 second by default.
 
+quota_mem_pressure_us
+---------------------
+
+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.
+
+Disabled by default.
+
+quota_autotune_feedback
+-----------------------
+
+User-specifiable feedback for auto-tuning of the effective quota.
+
+While keeping the caps that set by other quotas, DAMON_RECLAIM automatically
+increases and decreases the effective level of the quota aiming receiving this
+feedback of value ``10,000`` from the user.  DAMON_RECLAIM assumes the feedback
+value and the quota are positively proportional.  Value zero means disabling
+this auto-tuning feature.
+
+Disabled by default.
+
 wmarks_interval
 ---------------
 
-- 
2.39.2