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Message-Id: <20231213182729.587081-3-shr@devkernel.io>
Date: Wed, 13 Dec 2023 10:27:27 -0800
From: Stefan Roesch <shr@...kernel.io>
To: kernel-team@...com
Cc: shr@...kernel.io, akpm@...ux-foundation.org, david@...hat.com,
hannes@...xchg.org, riel@...riel.com, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: [PATCH v4 2/4] mm/ksm: add sysfs knobs for advisor
This adds four new knobs for the KSM advisor to influence its behaviour.
The knobs are:
- advisor_mode:
none: no advisor (default)
scan-time: scan time advisor
- advisor_max_cpu: 70 (default, cpu usage percent)
- advisor_min_pages_to_scan: 500 (default)
- advisor_max_pages_to_scan: 30000 (default)
- advisor_target_scan_time: 200 (default in seconds)
The new values will take effect on the next scan round.
Signed-off-by: Stefan Roesch <shr@...kernel.io>
---
mm/ksm.c | 142 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 139 insertions(+), 3 deletions(-)
diff --git a/mm/ksm.c b/mm/ksm.c
index 4f7b71a1f3112..f7387a6d02050 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -302,10 +302,10 @@ unsigned long ksm_zero_pages;
static unsigned long ksm_pages_skipped;
/* Don't scan more than max pages per batch. */
-static unsigned long ksm_advisor_max_pages = 30000;
+static unsigned long ksm_advisor_max_pages_to_scan = 30000;
/* At least scan this many pages per batch. */
-static unsigned long ksm_advisor_min_pages = 500;
+static unsigned long ksm_advisor_min_pages_to_scan = 500;
/* Min CPU for scanning pages per scan */
static unsigned int ksm_advisor_min_cpu = 10;
@@ -341,6 +341,16 @@ enum ksm_advisor_type {
};
static enum ksm_advisor_type ksm_advisor;
+static void set_advisor_defaults(void)
+{
+ if (ksm_advisor == KSM_ADVISOR_NONE) {
+ ksm_thread_pages_to_scan = DEFAULT_PAGES_TO_SCAN;
+ } else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) {
+ advisor_ctx = (const struct advisor_ctx){ 0 };
+ ksm_thread_pages_to_scan = ksm_advisor_min_pages_to_scan;
+ }
+}
+
static inline void advisor_start_scan(void)
{
if (ksm_advisor == KSM_ADVISOR_SCAN_TIME)
@@ -434,7 +444,7 @@ static void scan_time_advisor(void)
pages = min(pages, per_page_cost * ksm_advisor_max_cpu);
pages = max(pages, per_page_cost * ksm_advisor_min_cpu);
- pages = min(pages, ksm_advisor_max_pages);
+ pages = min(pages, ksm_advisor_max_pages_to_scan);
/* Update advisor context */
advisor_ctx.change = change;
@@ -3722,6 +3732,127 @@ static ssize_t smart_scan_store(struct kobject *kobj,
}
KSM_ATTR(smart_scan);
+static ssize_t advisor_mode_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ const char *output;
+
+ if (ksm_advisor == KSM_ADVISOR_NONE)
+ output = "[none] scan-time";
+ else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME)
+ output = "none [scan-time]";
+
+ return sysfs_emit(buf, "%s\n", output);
+}
+
+static ssize_t advisor_mode_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf,
+ size_t count)
+{
+ if (sysfs_streq("scan-time", buf))
+ ksm_advisor = KSM_ADVISOR_SCAN_TIME;
+ else if (sysfs_streq("none", buf))
+ ksm_advisor = KSM_ADVISOR_NONE;
+ else
+ return -EINVAL;
+
+ /* Set advisor default values */
+ set_advisor_defaults();
+
+ return count;
+}
+KSM_ATTR(advisor_mode);
+
+static ssize_t advisor_max_cpu_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%u\n", ksm_advisor_max_cpu);
+}
+
+static ssize_t advisor_max_cpu_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int err;
+ unsigned long value;
+
+ err = kstrtoul(buf, 10, &value);
+ if (err)
+ return -EINVAL;
+
+ ksm_advisor_max_cpu = value;
+ return count;
+}
+KSM_ATTR(advisor_max_cpu);
+
+static ssize_t advisor_min_pages_to_scan_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%lu\n", ksm_advisor_min_pages_to_scan);
+}
+
+static ssize_t advisor_min_pages_to_scan_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int err;
+ unsigned long value;
+
+ err = kstrtoul(buf, 10, &value);
+ if (err)
+ return -EINVAL;
+
+ ksm_advisor_min_pages_to_scan = value;
+ return count;
+}
+KSM_ATTR(advisor_min_pages_to_scan);
+
+static ssize_t advisor_max_pages_to_scan_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%lu\n", ksm_advisor_max_pages_to_scan);
+}
+
+static ssize_t advisor_max_pages_to_scan_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int err;
+ unsigned long value;
+
+ err = kstrtoul(buf, 10, &value);
+ if (err)
+ return -EINVAL;
+
+ ksm_advisor_max_pages_to_scan = value;
+ return count;
+}
+KSM_ATTR(advisor_max_pages_to_scan);
+
+static ssize_t advisor_target_scan_time_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%lu\n", ksm_advisor_target_scan_time);
+}
+
+static ssize_t advisor_target_scan_time_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int err;
+ unsigned long value;
+
+ err = kstrtoul(buf, 10, &value);
+ if (err)
+ return -EINVAL;
+ if (value < 1)
+ return -EINVAL;
+
+ ksm_advisor_target_scan_time = value;
+ return count;
+}
+KSM_ATTR(advisor_target_scan_time);
+
static struct attribute *ksm_attrs[] = {
&sleep_millisecs_attr.attr,
&pages_to_scan_attr.attr,
@@ -3744,6 +3875,11 @@ static struct attribute *ksm_attrs[] = {
&use_zero_pages_attr.attr,
&general_profit_attr.attr,
&smart_scan_attr.attr,
+ &advisor_mode_attr.attr,
+ &advisor_max_cpu_attr.attr,
+ &advisor_min_pages_to_scan_attr.attr,
+ &advisor_max_pages_to_scan_attr.attr,
+ &advisor_target_scan_time_attr.attr,
NULL,
};
--
2.39.3
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