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Date: Tue, 19 Oct 2021 15:07:20 +0000
From: SeongJae Park <sj@...nel.org>
To: akpm@...ux-foundation.org
Cc: SeongJae Park <sj@...nel.org>, Jonathan.Cameron@...wei.com,
amit@...nel.org, benh@...nel.crashing.org, corbet@....net,
david@...hat.com, dwmw@...zon.com, elver@...gle.com,
foersleo@...zon.de, gthelen@...gle.com, markubo@...zon.de,
rientjes@...gle.com, shakeelb@...gle.com, shuah@...nel.org,
linux-damon@...zon.com, linux-mm@...ck.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 04/15] 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 commit
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.
Signed-off-by: SeongJae Park <sj@...nel.org>
---
include/linux/damon.h | 25 +++++++++++++++++++-----
mm/damon/core.c | 45 ++++++++++++++++++++++++++++++++++++++-----
2 files changed, 60 insertions(+), 10 deletions(-)
diff --git a/include/linux/damon.h b/include/linux/damon.h
index 1fec32e18319..5347f940818e 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;
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 693b75bc3450..d1da4bef96ed 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -107,8 +107,12 @@ struct damos *damon_new_scheme(
scheme->stat_sz = 0;
INIT_LIST_HEAD(&scheme->list);
+ scheme->quota.ms = quota->ms;
scheme->quota.sz = quota->sz;
scheme->quota.reset_interval = quota->reset_interval;
+ scheme->quota.total_charged_sz = 0;
+ scheme->quota.total_charged_ns = 0;
+ scheme->quota.esz = 0;
scheme->quota.charged_sz = 0;
scheme->quota.charged_from = 0;
scheme->quota.charge_target_from = NULL;
@@ -550,9 +554,10 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
damon_for_each_scheme(s, c) {
struct damos_quota *quota = &s->quota;
unsigned long sz = r->ar.end - r->ar.start;
+ struct timespec64 begin, end;
/* Check the quota */
- if (quota->sz && quota->charged_sz >= quota->sz)
+ if (quota->esz && quota->charged_sz >= quota->esz)
continue;
/* Skip previously charged regions */
@@ -597,16 +602,21 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
/* Apply the scheme */
if (c->primitive.apply_scheme) {
- if (quota->sz && quota->charged_sz + sz > quota->sz) {
- sz = ALIGN_DOWN(quota->sz - quota->charged_sz,
+ if (quota->esz &&
+ quota->charged_sz + sz > quota->esz) {
+ sz = ALIGN_DOWN(quota->esz - quota->charged_sz,
DAMON_MIN_REGION);
if (!sz)
goto update_stat;
damon_split_region_at(c, t, r, sz);
}
+ ktime_get_coarse_ts64(&begin);
c->primitive.apply_scheme(c, t, r, s);
+ ktime_get_coarse_ts64(&end);
+ quota->total_charged_ns += timespec64_to_ns(&end) -
+ timespec64_to_ns(&begin);
quota->charged_sz += sz;
- if (quota->sz && quota->charged_sz >= quota->sz) {
+ if (quota->esz && quota->charged_sz >= quota->esz) {
quota->charge_target_from = t;
quota->charge_addr_from = r->ar.end + 1;
}
@@ -620,6 +630,29 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
}
}
+/* Shouldn't be called if quota->ms and quota->sz are zero */
+static void damos_set_effective_quota(struct damos_quota *quota)
+{
+ unsigned long throughput;
+ unsigned long esz;
+
+ if (!quota->ms) {
+ quota->esz = quota->sz;
+ return;
+ }
+
+ if (quota->total_charged_ns)
+ throughput = quota->total_charged_sz * 1000000 /
+ quota->total_charged_ns;
+ else
+ throughput = PAGE_SIZE * 1024;
+ esz = throughput * quota->ms;
+
+ if (quota->sz && quota->sz < esz)
+ esz = quota->sz;
+ quota->esz = esz;
+}
+
static void kdamond_apply_schemes(struct damon_ctx *c)
{
struct damon_target *t;
@@ -629,15 +662,17 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
damon_for_each_scheme(s, c) {
struct damos_quota *quota = &s->quota;
- if (!quota->sz)
+ if (!quota->ms && !quota->sz)
continue;
/* New charge window starts */
if (time_after_eq(jiffies, quota->charged_from +
msecs_to_jiffies(
quota->reset_interval))) {
+ quota->total_charged_sz += quota->charged_sz;
quota->charged_from = jiffies;
quota->charged_sz = 0;
+ damos_set_effective_quota(quota);
}
}
--
2.17.1
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