User-explicit quotas (size and time quotas) having zero value means the
quotas are unset. And, effective size quota is set as the minimum value
of the explicit quotas. When quota goals are set, the goal-based quota
tuner can make it lower. But the existing only single tuner never sets
the effective size quota zero. Because of the fact, DAMON core assumes
zero effective quota means the user has set no quota.
Multiple tuners are now allowed, though. In the future, some tuners
might want to set a zero effective size quota. There is no reason to
restrict that. Meanwhile, because of the current implementation, it
will only deactivate all quotas and make the scheme work at its full
speed.
Introduce a dedicated function for checking if no quota is set. The
function checks the fact by showing if the user-set explicit quotas are
zero and no goal is installed. It is decoupled from zero effective
quota, and hence allows future tuners set zero effective quota for
intentionally deactivating the scheme by a purpose.
Signed-off-by: SeongJae Park <sj@kernel.org>
---
mm/damon/core.c | 29 ++++++++++++++++++++++++-----
1 file changed, 24 insertions(+), 5 deletions(-)
diff --git a/mm/damon/core.c b/mm/damon/core.c
index c5503fdb10bb7..d657b87dd99e8 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -387,6 +387,11 @@ void damos_destroy_quota_goal(struct damos_quota_goal *g)
damos_free_quota_goal(g);
}
+static bool damos_quota_goals_empty(struct damos_quota *q)
+{
+ return list_empty(&q->goals);
+}
+
/* initialize fields of @quota that normally API users wouldn't set */
static struct damos_quota *damos_quota_init(struct damos_quota *quota)
{
@@ -1782,12 +1787,24 @@ static bool __damos_valid_target(struct damon_region *r, struct damos *s)
r->age <= s->pattern.max_age_region;
}
+/*
+ * damos_quota_set() - Return if the given quota is actually set.
+ * @quota: The quota to check.
+ *
+ * Returns true if the quota is set, false otherwise.
+ */
+static bool damos_quota_set(struct damos_quota *quota)
+{
+ return quota->esz || quota->sz || quota->ms ||
+ !damos_quota_goals_empty(quota);
+}
+
static bool damos_valid_target(struct damon_ctx *c, struct damon_region *r,
struct damos *s)
{
bool ret = __damos_valid_target(r, s);
- if (!ret || !s->quota.esz || !c->ops.get_scheme_score)
+ if (!ret || !damos_quota_set(&s->quota) || !c->ops.get_scheme_score)
return ret;
return c->ops.get_scheme_score(c, r, s) >= s->quota.min_score;
@@ -2057,7 +2074,8 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t,
}
if (c->ops.apply_scheme) {
- if (quota->esz && quota->charged_sz + sz > quota->esz) {
+ if (damos_quota_set(quota) &&
+ quota->charged_sz + sz > quota->esz) {
sz = ALIGN_DOWN(quota->esz - quota->charged_sz,
c->min_region_sz);
if (!sz)
@@ -2076,7 +2094,8 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t,
quota->total_charged_ns += timespec64_to_ns(&end) -
timespec64_to_ns(&begin);
quota->charged_sz += sz;
- if (quota->esz && quota->charged_sz >= quota->esz) {
+ if (damos_quota_set(quota) &&
+ quota->charged_sz >= quota->esz) {
quota->charge_target_from = t;
quota->charge_addr_from = r->ar.end + 1;
}
@@ -2104,7 +2123,7 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
continue;
/* Check the quota */
- if (quota->esz && quota->charged_sz >= quota->esz)
+ if (damos_quota_set(quota) && quota->charged_sz >= quota->esz)
continue;
if (damos_skip_charged_region(t, r, s, c->min_region_sz))
@@ -2389,7 +2408,7 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s)
/* New charge window starts */
if (time_after_eq(jiffies, quota->charged_from +
msecs_to_jiffies(quota->reset_interval))) {
- if (quota->esz && quota->charged_sz >= quota->esz)
+ if (damos_quota_set(quota) && quota->charged_sz >= quota->esz)
s->stat.qt_exceeds++;
quota->total_charged_sz += quota->charged_sz;
quota->charged_from = jiffies;
--
2.47.3
On 3/4/2026 7:41 AM, SeongJae Park wrote:
I find the name of this function confusing. The function doesn't
actually set anything. Maybe better damos_quota_is_set()
> +/*
> + * damos_quota_set() - Return if the given quota is actually set.
> + * @quota: The quota to check.
> + *
> + * Returns true if the quota is set, false otherwise.
> + */
> +static bool damos_quota_set(struct damos_quota *quota)
> +{
> + return quota->esz || quota->sz || quota->ms ||
> + !damos_quota_goals_empty(quota);
> +}
> +
--
Asier Gutierrez
Huawei
On Wed, 4 Mar 2026 13:18:16 +0300 Gutierrez Asier <gutierrez.asier@huawei-partners.com> wrote:
>
>
> On 3/4/2026 7:41 AM, SeongJae Park wrote:
>
> I find the name of this function confusing. The function doesn't
> actually set anything. Maybe better damos_quota_is_set()
> > +/*
> > + * damos_quota_set() - Return if the given quota is actually set.
> > + * @quota: The quota to check.
> > + *
> > + * Returns true if the quota is set, false otherwise.
> > + */
> > +static bool damos_quota_set(struct damos_quota *quota)
> > +{
> > + return quota->esz || quota->sz || quota->ms ||
> > + !damos_quota_goals_empty(quota);
> > +}
> > +
Thank you for the nice suggestion, I agree your points and like the suggested
name!
Andrew, if you pick this patch to mm-new for more reviews, could you please add
below attaching fixup together?
Thanks,
SJ
[...]
=== >8 ===
From 9599524cc5e5bbe8263c847b6f20f0aa919b3853 Mon Sep 17 00:00:00 2001
From: SeongJae Park <sj@kernel.org>
Date: Wed, 4 Mar 2026 06:46:55 -0800
Subject: [PATCH] mm/damon/core: rename damos_quota_set() to
damos_quota_is_set()
damos_quota_set() can be confused as a sort of setter function. Rename.
Suggested-by: Gutierrez Asier <gutierrez.asier@huawei-partners.com>
Signed-off-by: SeongJae Park <sj@kernel.org>
---
mm/damon/core.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/mm/damon/core.c b/mm/damon/core.c
index d657b87dd99e8..c58430a4cd6ef 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1788,12 +1788,12 @@ static bool __damos_valid_target(struct damon_region *r, struct damos *s)
}
/*
- * damos_quota_set() - Return if the given quota is actually set.
+ * damos_quota_is_set() - Return if the given quota is actually set.
* @quota: The quota to check.
*
* Returns true if the quota is set, false otherwise.
*/
-static bool damos_quota_set(struct damos_quota *quota)
+static bool damos_quota_is_set(struct damos_quota *quota)
{
return quota->esz || quota->sz || quota->ms ||
!damos_quota_goals_empty(quota);
@@ -1804,7 +1804,7 @@ static bool damos_valid_target(struct damon_ctx *c, struct damon_region *r,
{
bool ret = __damos_valid_target(r, s);
- if (!ret || !damos_quota_set(&s->quota) || !c->ops.get_scheme_score)
+ if (!ret || !damos_quota_is_set(&s->quota) || !c->ops.get_scheme_score)
return ret;
return c->ops.get_scheme_score(c, r, s) >= s->quota.min_score;
@@ -2074,7 +2074,7 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t,
}
if (c->ops.apply_scheme) {
- if (damos_quota_set(quota) &&
+ if (damos_quota_is_set(quota) &&
quota->charged_sz + sz > quota->esz) {
sz = ALIGN_DOWN(quota->esz - quota->charged_sz,
c->min_region_sz);
@@ -2094,7 +2094,7 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t,
quota->total_charged_ns += timespec64_to_ns(&end) -
timespec64_to_ns(&begin);
quota->charged_sz += sz;
- if (damos_quota_set(quota) &&
+ if (damos_quota_is_set(quota) &&
quota->charged_sz >= quota->esz) {
quota->charge_target_from = t;
quota->charge_addr_from = r->ar.end + 1;
@@ -2123,7 +2123,8 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
continue;
/* Check the quota */
- if (damos_quota_set(quota) && quota->charged_sz >= quota->esz)
+ if (damos_quota_is_set(quota) &&
+ quota->charged_sz >= quota->esz)
continue;
if (damos_skip_charged_region(t, r, s, c->min_region_sz))
@@ -2408,7 +2409,8 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s)
/* New charge window starts */
if (time_after_eq(jiffies, quota->charged_from +
msecs_to_jiffies(quota->reset_interval))) {
- if (damos_quota_set(quota) && quota->charged_sz >= quota->esz)
+ if (damos_quota_is_set(quota) &&
+ quota->charged_sz >= quota->esz)
s->stat.qt_exceeds++;
quota->total_charged_sz += quota->charged_sz;
quota->charged_from = jiffies;
--
2.47.3
On Wed, 4 Mar 2026 06:51:39 -0800 SeongJae Park <sj@kernel.org> wrote:
> On Wed, 4 Mar 2026 13:18:16 +0300 Gutierrez Asier <gutierrez.asier@huawei-partners.com> wrote:
>
> >
> >
> > On 3/4/2026 7:41 AM, SeongJae Park wrote:
> >
> > I find the name of this function confusing. The function doesn't
> > actually set anything. Maybe better damos_quota_is_set()
> > > +/*
> > > + * damos_quota_set() - Return if the given quota is actually set.
> > > + * @quota: The quota to check.
> > > + *
> > > + * Returns true if the quota is set, false otherwise.
> > > + */
> > > +static bool damos_quota_set(struct damos_quota *quota)
> > > +{
> > > + return quota->esz || quota->sz || quota->ms ||
> > > + !damos_quota_goals_empty(quota);
> > > +}
> > > +
>
> Thank you for the nice suggestion, I agree your points and like the suggested
> name!
>
> Andrew, if you pick this patch to mm-new for more reviews, could you please add
> below attaching fixup together?
Never mind. This is an RFC, which is not aiming to be merged into mm-new.
I'll squash the fixup to next spin of this patch.
Thanks,
SJ
[...]
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