mm/damon/schemes: implement time quota

The size quota feature of DAMOS is useful for IO resource-critical
systems, but not so intuitive for CPU time-critical systems.  Systems
using zram or zswap-like swap device would be examples.

To provide another intuitive ways for such systems, this implements
time-based quota for DAMON-based Operation Schemes.  If the quota is
set, DAMOS tries to use only up to the user-defined quota of CPU time
within a given time window.

Link: https://lkml.kernel.org/r/20211019150731.16699-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 20 insertions, 5 deletions

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 585d985768fd..1e7671bf3d23 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -91,20 +91,35 @@ enum damos_action {
 
 /**
  * struct damos_quota - Controls the aggressiveness of the given scheme.
+ * @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.
  *
  * To avoid consuming too much CPU time or IO resources for applying the
- * &struct damos->action to large memory, DAMON allows users to set a size
- * quota.  The quota can be set by writing non-zero values to &sz.  If the size
- * quota is set, DAMON tries to apply the action only up to &sz bytes within
- * &reset_interval.
+ * &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
+ * &sz, respectively.  If the time quota is set, DAMON tries to use only up to
+ * &ms milliseconds within &reset_interval for applying the action.  If the
+ * size quota is set, DAMON tries to apply the action only up to &sz bytes
+ * within &reset_interval.
+ *
+ * Internally, the time quota is transformed to a size quota using estimated
+ * throughput of the scheme's action.  DAMON then compares it against &sz and
+ * uses smaller one as the effective quota.
  */
 struct damos_quota {
+	unsigned long ms;
 	unsigned long sz;
 	unsigned long reset_interval;
 
-/* private: For charging the quota */
+/* 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;
 	struct damon_target *charge_target_from;