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sched/mmcid: Convert mm CID mask to a bitmap

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This is truly a bitmap and just conveniently uses a cpumask because the
maximum size of the bitmap is nr_cpu_ids.

But that prevents to do searches for a zero bit in a limited range, which
is helpful to provide an efficient mechanism to consolidate the CID space
when the number of users decreases.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Link: https://patch.msgid.link/20251119172549.642866767@linutronix.de
This commit is contained in:
Thomas Gleixner
2025-11-19 18:27:03 +01:00
parent 35a5c37cb9
commit 539115f08c
3 changed files with 9 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
include/linux/mm_types.h
View File

@@ -1342,13 +1342,13 @@ static inline cpumask_t *mm_cpus_allowed(struct mm_struct *mm)
}
/* Accessor for struct mm_struct's cidmask. */
static inline cpumask_t *mm_cidmask(struct mm_struct *mm)
static inline unsigned long *mm_cidmask(struct mm_struct *mm)
{
unsigned long cid_bitmap = (unsigned long)mm_cpus_allowed(mm);
/* Skip mm_cpus_allowed */
cid_bitmap += cpumask_size();
return (struct cpumask *)cid_bitmap;
return (unsigned long *)cid_bitmap;
}
static inline void mm_init_cid(struct mm_struct *mm, struct task_struct *p)
@@ -1363,7 +1363,7 @@ static inline void mm_init_cid(struct mm_struct *mm, struct task_struct *p)
mm->mm_cid.nr_cpus_allowed = p->nr_cpus_allowed;
raw_spin_lock_init(&mm->mm_cid.lock);
cpumask_copy(mm_cpus_allowed(mm), &p->cpus_mask);
cpumask_clear(mm_cidmask(mm));
bitmap_zero(mm_cidmask(mm), num_possible_cpus());
}
static inline int mm_alloc_cid_noprof(struct mm_struct *mm, struct task_struct *p)
@@ -1384,7 +1384,8 @@ static inline void mm_destroy_cid(struct mm_struct *mm)
static inline unsigned int mm_cid_size(void)
{
return 2 * cpumask_size(); /* mm_cpus_allowed(), mm_cidmask(). */
/* mm_cpus_allowed(), mm_cidmask(). */
return cpumask_size() + bitmap_size(num_possible_cpus());
}
#else /* CONFIG_SCHED_MM_CID */

2
kernel/sched/core.c
View File

@@ -10402,7 +10402,7 @@ void sched_mm_cid_exit_signals(struct task_struct *t)
guard(preempt)();
t->mm_cid.active = 0;
if (t->mm_cid.cid != MM_CID_UNSET) {
cpumask_clear_cpu(t->mm_cid.cid, mm_cidmask(mm));
clear_bit(t->mm_cid.cid, mm_cidmask(mm));
t->mm_cid.cid = MM_CID_UNSET;
}
}

6
kernel/sched/sched.h
View File

@@ -3559,7 +3559,7 @@ static inline bool __mm_cid_get(struct task_struct *t, unsigned int cid, unsigne
if (cid >= max_cids)
return false;
if (cpumask_test_and_set_cpu(cid, mm_cidmask(mm)))
if (test_and_set_bit(cid, mm_cidmask(mm)))
return false;
t->mm_cid.cid = t->mm_cid.last_cid = cid;
__this_cpu_write(mm->mm_cid.pcpu->cid, cid);
@@ -3582,7 +3582,7 @@ static inline bool mm_cid_get(struct task_struct *t)
return true;
/* Try the first zero bit in the cidmask. */
return __mm_cid_get(t, cpumask_first_zero(mm_cidmask(mm)), max_cids);
return __mm_cid_get(t, find_first_zero_bit(mm_cidmask(mm), num_possible_cpus()), max_cids);
}
static inline void mm_cid_select(struct task_struct *t)
@@ -3603,7 +3603,7 @@ static inline void switch_mm_cid(struct task_struct *prev, struct task_struct *n
{
if (prev->mm_cid.active) {
if (prev->mm_cid.cid != MM_CID_UNSET)
cpumask_clear_cpu(prev->mm_cid.cid, mm_cidmask(prev->mm));
clear_bit(prev->mm_cid.cid, mm_cidmask(prev->mm));
prev->mm_cid.cid = MM_CID_UNSET;
}