[v2,2/4] mm/ksm: add sysfs knobs for advisor
Commit Message
This adds four new knobs for the KSM advisor to influence its behaviour.
The knobs are:
- advisor_mode:
0: no advisor (default)
1: scan time advisor
- advisor_min_cpu: 15 (default, cpu usage percent)
- advisor_max_cpu: 70 (default, cpu usage percent)
- advisor_min_pages: 500 (default)
- advisor_max_pages: 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@devkernel.io>
---
mm/ksm.c | 154 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 154 insertions(+)
Comments
On 28.10.23 02:09, Stefan Roesch wrote:
> This adds four new knobs for the KSM advisor to influence its behaviour.
>
> The knobs are:
> - advisor_mode:
> 0: no advisor (default)
> 1: scan time advisor
> - advisor_min_cpu: 15 (default, cpu usage percent)
> - advisor_max_cpu: 70 (default, cpu usage percent)
> - advisor_min_pages: 500 (default)
> - advisor_max_pages: 30000 (default)
> - advisor_target_scan_time: 200 (default in seconds)
Is there a way we can avoid exposing advisor_min_pages/advisor_max_pages
and just have this internal e.g., as defines?
On 28.10.23 02:09, Stefan Roesch wrote:
> This adds four new knobs for the KSM advisor to influence its behaviour.
>
> The knobs are:
> - advisor_mode:
> 0: no advisor (default)
> 1: scan time advisor
> - advisor_min_cpu: 15 (default, cpu usage percent)
> - advisor_max_cpu: 70 (default, cpu usage percent)
> - advisor_min_pages: 500 (default)
> - advisor_max_pages: 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@devkernel.io>
> ---
> mm/ksm.c | 154 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 154 insertions(+)
>
> diff --git a/mm/ksm.c b/mm/ksm.c
> index e18fecfb359d..042ecaeb0beb 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -351,6 +351,14 @@ static void init_advisor(void)
> advisor_ctx.cpu_time = 0;
> }
[...]
> * Use previous scan time if available, otherwise use current scan time as an
> * approximation for the previous scan time.
> @@ -3719,6 +3727,146 @@ 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)
> +{
> + return sysfs_emit(buf, "%u\n", ksm_advisor);
> +}
> +
> +static ssize_t advisor_mode_store(struct kobject *kobj,
> + struct kobj_attribute *attr, const char *buf,
> + size_t count)
> +{
> + unsigned int mode;
> + int err;
> +
> + err = kstrtouint(buf, 10, &mode);
> + if (err)
> + return -EINVAL;
> + if (mode > KSM_ADVISOR_LAST)
> + return -EINVAL;
> +
> + /* Set advisor default values */
> + ksm_advisor = mode;
> + init_advisor();
> + set_advisor_defaults();
> +
> + return count;
Can we instead use human-readable strings?
"none" and "scan-time" should be clearer.
David Hildenbrand <david@redhat.com> writes:
> On 28.10.23 02:09, Stefan Roesch wrote:
>> This adds four new knobs for the KSM advisor to influence its behaviour.
>> The knobs are:
>> - advisor_mode:
>> 0: no advisor (default)
>> 1: scan time advisor
>> - advisor_min_cpu: 15 (default, cpu usage percent)
>> - advisor_max_cpu: 70 (default, cpu usage percent)
>> - advisor_min_pages: 500 (default)
>> - advisor_max_pages: 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@devkernel.io>
>> ---
>> mm/ksm.c | 154 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 154 insertions(+)
>> diff --git a/mm/ksm.c b/mm/ksm.c
>> index e18fecfb359d..042ecaeb0beb 100644
>> --- a/mm/ksm.c
>> +++ b/mm/ksm.c
>> @@ -351,6 +351,14 @@ static void init_advisor(void)
>> advisor_ctx.cpu_time = 0;
>> }
>
>
> [...]
>
>> * Use previous scan time if available, otherwise use current scan time as an
>> * approximation for the previous scan time.
>> @@ -3719,6 +3727,146 @@ 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)
>> +{
>> + return sysfs_emit(buf, "%u\n", ksm_advisor);
>> +}
>> +
>> +static ssize_t advisor_mode_store(struct kobject *kobj,
>> + struct kobj_attribute *attr, const char *buf,
>> + size_t count)
>> +{
>> + unsigned int mode;
>> + int err;
>> +
>> + err = kstrtouint(buf, 10, &mode);
>> + if (err)
>> + return -EINVAL;
>> + if (mode > KSM_ADVISOR_LAST)
>> + return -EINVAL;
>> +
>> + /* Set advisor default values */
>> + ksm_advisor = mode;
>> + init_advisor();
>> + set_advisor_defaults();
>> +
>> + return count;
>
> Can we instead use human-readable strings?
>
> "none" and "scan-time" should be clearer.
>
I'll change the interface to use strings instead of numbers.
David Hildenbrand <david@redhat.com> writes:
> On 28.10.23 02:09, Stefan Roesch wrote:
>> This adds four new knobs for the KSM advisor to influence its behaviour.
>> The knobs are:
>> - advisor_mode:
>> 0: no advisor (default)
>> 1: scan time advisor
>> - advisor_min_cpu: 15 (default, cpu usage percent)
>> - advisor_max_cpu: 70 (default, cpu usage percent)
>> - advisor_min_pages: 500 (default)
>> - advisor_max_pages: 30000 (default)
>> - advisor_target_scan_time: 200 (default in seconds)
>
> Is there a way we can avoid exposing advisor_min_pages/advisor_max_pages and
> just have this internal e.g., as defines?
>
Yes, we can.
David Hildenbrand <david@redhat.com> writes:
> On 28.10.23 02:09, Stefan Roesch wrote:
>> This adds four new knobs for the KSM advisor to influence its behaviour.
>> The knobs are:
>> - advisor_mode:
>> 0: no advisor (default)
>> 1: scan time advisor
>> - advisor_min_cpu: 15 (default, cpu usage percent)
>> - advisor_max_cpu: 70 (default, cpu usage percent)
>> - advisor_min_pages: 500 (default)
>> - advisor_max_pages: 30000 (default)
>> - advisor_target_scan_time: 200 (default in seconds)
>
> Is there a way we can avoid exposing advisor_min_pages/advisor_max_pages and
> just have this internal e.g., as defines?
Yes, we can.
@@ -351,6 +351,14 @@ static void init_advisor(void)
advisor_ctx.cpu_time = 0;
}
+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)
+ ksm_thread_pages_to_scan = ksm_advisor_min_pages;
+}
+
/*
* Use previous scan time if available, otherwise use current scan time as an
* approximation for the previous scan time.
@@ -3719,6 +3727,146 @@ 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)
+{
+ return sysfs_emit(buf, "%u\n", ksm_advisor);
+}
+
+static ssize_t advisor_mode_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf,
+ size_t count)
+{
+ unsigned int mode;
+ int err;
+
+ err = kstrtouint(buf, 10, &mode);
+ if (err)
+ return -EINVAL;
+ if (mode > KSM_ADVISOR_LAST)
+ return -EINVAL;
+
+ /* Set advisor default values */
+ ksm_advisor = mode;
+ init_advisor();
+ set_advisor_defaults();
+
+ return count;
+}
+KSM_ATTR(advisor_mode);
+
+static ssize_t advisor_min_cpu_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%u\n", ksm_advisor_min_cpu);
+}
+
+static ssize_t advisor_min_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_min_cpu = value;
+ return count;
+}
+KSM_ATTR(advisor_min_cpu);
+
+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_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%lu\n", ksm_advisor_min_pages);
+}
+
+static ssize_t advisor_min_pages_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 = value;
+ return count;
+}
+KSM_ATTR(advisor_min_pages);
+
+static ssize_t advisor_max_pages_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%lu\n", ksm_advisor_max_pages);
+}
+
+static ssize_t advisor_max_pages_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 = value;
+ return count;
+}
+KSM_ATTR(advisor_max_pages);
+
+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,
@@ -3741,6 +3889,12 @@ static struct attribute *ksm_attrs[] = {
&use_zero_pages_attr.attr,
&general_profit_attr.attr,
&smart_scan_attr.attr,
+ &advisor_mode_attr.attr,
+ &advisor_min_cpu_attr.attr,
+ &advisor_max_cpu_attr.attr,
+ &advisor_min_pages_attr.attr,
+ &advisor_max_pages_attr.attr,
+ &advisor_target_scan_time_attr.attr,
NULL,
};