Keep track of the currently allocated mm_cid for each mm/cpu rather than
freeing them immediately. This eliminates most atomic ops when context
switching back and forth between threads belonging to different memory
spaces in multi-threaded scenarios (many processes, each with many
threads).
This patch is based on v6.3-rc4 with this patch applied:
("mm: Fix memory leak on mm_init error handling")
https://lore.kernel.org/lkml/[email protected]/
Signed-off-by: Mathieu Desnoyers <[email protected]>
Cc: Aaron Lu <[email protected]>
Cc: Peter Zijlstra <[email protected]>
---
include/linux/mm_types.h | 32 ++++++++++++++++
kernel/fork.c | 7 +++-
kernel/sched/core.c | 79 ++++++++++++++++++++++++++++++++++-----
kernel/sched/sched.h | 81 ++++++++++++++++++++++++++++++----------
4 files changed, 169 insertions(+), 30 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 0722859c3647..335af2da5b34 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -609,6 +609,7 @@ struct mm_struct {
* were being concurrently updated by the updaters.
*/
raw_spinlock_t cid_lock;
+ int __percpu *pcpu_cid;
#endif
#ifdef CONFIG_MMU
atomic_long_t pgtables_bytes; /* size of all page tables */
@@ -872,6 +873,16 @@ static inline void vma_iter_init(struct vma_iterator *vmi,
}
#ifdef CONFIG_SCHED_MM_CID
+
+enum pcpu_cid_state {
+ PCPU_CID_UNSET = -1U,
+};
+
+static inline bool pcpu_cid_is_unset(int cid)
+{
+ return cid == PCPU_CID_UNSET;
+}
+
/* Accessor for struct mm_struct's cidmask. */
static inline cpumask_t *mm_cidmask(struct mm_struct *mm)
{
@@ -885,16 +896,37 @@ static inline cpumask_t *mm_cidmask(struct mm_struct *mm)
static inline void mm_init_cid(struct mm_struct *mm)
{
+ int i;
+
raw_spin_lock_init(&mm->cid_lock);
+ for_each_possible_cpu(i)
+ *per_cpu_ptr(mm->pcpu_cid, i) = PCPU_CID_UNSET;
cpumask_clear(mm_cidmask(mm));
}
+static inline int mm_alloc_cid(struct mm_struct *mm)
+{
+ mm->pcpu_cid = alloc_percpu(int);
+ if (!mm->pcpu_cid)
+ return -ENOMEM;
+ mm_init_cid(mm);
+ return 0;
+}
+
+static inline void mm_destroy_cid(struct mm_struct *mm)
+{
+ free_percpu(mm->pcpu_cid);
+ mm->pcpu_cid = NULL;
+}
+
static inline unsigned int mm_cid_size(void)
{
return cpumask_size();
}
#else /* CONFIG_SCHED_MM_CID */
static inline void mm_init_cid(struct mm_struct *mm) { }
+static inline int mm_alloc_cid(struct mm_struct *mm) { return 0; }
+static inline void mm_destroy_cid(struct mm_struct *mm) { }
static inline unsigned int mm_cid_size(void)
{
return 0;
diff --git a/kernel/fork.c b/kernel/fork.c
index c983c4fe3090..57fdc96ffa49 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -790,6 +790,7 @@ void __mmdrop(struct mm_struct *mm)
check_mm(mm);
put_user_ns(mm->user_ns);
mm_pasid_drop(mm);
+ mm_destroy_cid(mm);
for (i = 0; i < NR_MM_COUNTERS; i++)
percpu_counter_destroy(&mm->rss_stat[i]);
@@ -1159,18 +1160,22 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
if (init_new_context(p, mm))
goto fail_nocontext;
+ if (mm_alloc_cid(mm))
+ goto fail_cid;
+
for (i = 0; i < NR_MM_COUNTERS; i++)
if (percpu_counter_init(&mm->rss_stat[i], 0, GFP_KERNEL_ACCOUNT))
goto fail_pcpu;
mm->user_ns = get_user_ns(user_ns);
lru_gen_init_mm(mm);
- mm_init_cid(mm);
return mm;
fail_pcpu:
while (i > 0)
percpu_counter_destroy(&mm->rss_stat[--i]);
+ mm_destroy_cid(mm);
+fail_cid:
destroy_context(mm);
fail_nocontext:
mm_free_pgd(mm);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0d18c3969f90..f07b87d155bd 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2326,16 +2326,20 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
struct task_struct *p, int new_cpu)
{
+ int cid;
+
lockdep_assert_rq_held(rq);
deactivate_task(rq, p, DEQUEUE_NOCLOCK);
set_task_cpu(p, new_cpu);
+ cid = sched_mm_cid_migrate_from(rq, p);
rq_unlock(rq, rf);
rq = cpu_rq(new_cpu);
rq_lock(rq, rf);
WARN_ON_ONCE(task_cpu(p) != new_cpu);
+ sched_mm_cid_migrate_to(rq, p, cid);
activate_task(rq, p, 0);
check_preempt_curr(rq, p, 0);
@@ -11383,45 +11387,102 @@ void call_trace_sched_update_nr_running(struct rq *rq, int count)
}
#ifdef CONFIG_SCHED_MM_CID
+/*
+ * Migration is from src cpu to dst cpu. Always called from stopper thread on
+ * src cpu with rq lock held.
+ */
+int sched_mm_cid_migrate_from(struct rq *src_rq, struct task_struct *t)
+{
+ struct mm_struct *mm = t->mm;
+ int src_cpu, src_cid;
+ int *src_pcpu_cid;
+
+ if (!mm)
+ return PCPU_CID_UNSET;
+
+ src_cpu = cpu_of(src_rq);
+ src_pcpu_cid = per_cpu_ptr(mm->pcpu_cid, src_cpu);
+ src_cid = *src_pcpu_cid;
+ if (pcpu_cid_is_unset(src_cid)) {
+ /* src_cid is unset, nothing to clear/grab. */
+ return PCPU_CID_UNSET;
+ }
+ /* Set to PCPU_CID_UNSET, grab ownership. */
+ *src_pcpu_cid = PCPU_CID_UNSET;
+ return src_cid;
+}
+
+void sched_mm_cid_migrate_to(struct rq *dst_rq, struct task_struct *t, int src_cid)
+{
+ struct mm_struct *mm = t->mm;
+ int dst_cpu, dst_cid;
+ int *dst_pcpu_cid;
+
+ if (!mm || pcpu_cid_is_unset(src_cid))
+ return;
+
+ dst_cpu = cpu_of(dst_rq);
+ dst_pcpu_cid = per_cpu_ptr(mm->pcpu_cid, dst_cpu);
+
+ /* *dst_pcpu_cid = min(src_cid, *dst_pcpu_cid) */
+ dst_cid = *dst_pcpu_cid;
+ if (!pcpu_cid_is_unset(dst_cid) && dst_cid < src_cid) {
+ __mm_cid_put(mm, src_cid);
+ return;
+ }
+ *dst_pcpu_cid = src_cid;
+ if (!pcpu_cid_is_unset(dst_cid)) {
+ /*
+ * Put dst_cid if not currently in use, else it will be
+ * lazy put.
+ */
+ if (dst_rq->curr->mm != mm)
+ __mm_cid_put(mm, dst_cid);
+ }
+}
+
void sched_mm_cid_exit_signals(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
- unsigned long flags;
+ struct rq *rq = this_rq();
+ struct rq_flags rf;
if (!mm)
return;
- local_irq_save(flags);
+ rq_lock_irqsave(rq, &rf);
mm_cid_put(mm, t->mm_cid);
t->mm_cid = -1;
t->mm_cid_active = 0;
- local_irq_restore(flags);
+ rq_unlock_irqrestore(rq, &rf);
}
void sched_mm_cid_before_execve(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
- unsigned long flags;
+ struct rq *rq = this_rq();
+ struct rq_flags rf;
if (!mm)
return;
- local_irq_save(flags);
+ rq_lock_irqsave(rq, &rf);
mm_cid_put(mm, t->mm_cid);
t->mm_cid = -1;
t->mm_cid_active = 0;
- local_irq_restore(flags);
+ rq_unlock_irqrestore(rq, &rf);
}
void sched_mm_cid_after_execve(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
- unsigned long flags;
+ struct rq *rq = this_rq();
+ struct rq_flags rf;
if (!mm)
return;
- local_irq_save(flags);
+ rq_lock_irqsave(rq, &rf);
t->mm_cid = mm_cid_get(mm);
t->mm_cid_active = 1;
- local_irq_restore(flags);
+ rq_unlock_irqrestore(rq, &rf);
rseq_set_notify_resume(t);
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 3e8df6d31c1e..7b93847b89a3 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3249,7 +3249,47 @@ static inline void update_current_exec_runtime(struct task_struct *curr,
}
#ifdef CONFIG_SCHED_MM_CID
-static inline int __mm_cid_get(struct mm_struct *mm)
+extern int sched_mm_cid_migrate_from(struct rq *src_rq, struct task_struct *t);
+extern void sched_mm_cid_migrate_to(struct rq *dst_rq, struct task_struct *t, int cid);
+
+static inline void __mm_cid_put(struct mm_struct *mm, int cid)
+{
+ lockdep_assert_irqs_disabled();
+ if (cid < 0)
+ return;
+ raw_spin_lock(&mm->cid_lock);
+ __cpumask_clear_cpu(cid, mm_cidmask(mm));
+ raw_spin_unlock(&mm->cid_lock);
+}
+
+static inline void mm_cid_put(struct mm_struct *mm, int thread_cid)
+{
+ int *pcpu_cid, cid;
+
+ lockdep_assert_irqs_disabled();
+ if (thread_cid < 0)
+ return;
+ pcpu_cid = this_cpu_ptr(mm->pcpu_cid);
+ cid = *pcpu_cid;
+ if (cid == thread_cid)
+ *pcpu_cid = PCPU_CID_UNSET;
+ __mm_cid_put(mm, thread_cid);
+}
+
+static inline void mm_cid_put_lazy(struct mm_struct *mm, int thread_cid)
+{
+ int *pcpu_cid, cid;
+
+ lockdep_assert_irqs_disabled();
+ if (thread_cid < 0)
+ return;
+ pcpu_cid = this_cpu_ptr(mm->pcpu_cid);
+ cid = *pcpu_cid;
+ if (cid != thread_cid)
+ __mm_cid_put(mm, thread_cid);
+}
+
+static inline int __mm_cid_get_locked(struct mm_struct *mm)
{
struct cpumask *cpumask;
int cid;
@@ -3262,40 +3302,38 @@ static inline int __mm_cid_get(struct mm_struct *mm)
return cid;
}
-static inline void mm_cid_put(struct mm_struct *mm, int cid)
+static inline int __mm_cid_get(struct mm_struct *mm)
{
+ int ret;
+
lockdep_assert_irqs_disabled();
- if (cid < 0)
- return;
raw_spin_lock(&mm->cid_lock);
- __cpumask_clear_cpu(cid, mm_cidmask(mm));
+ ret = __mm_cid_get_locked(mm);
raw_spin_unlock(&mm->cid_lock);
+ return ret;
}
static inline int mm_cid_get(struct mm_struct *mm)
{
- int ret;
+ int *pcpu_cid, cid;
lockdep_assert_irqs_disabled();
- raw_spin_lock(&mm->cid_lock);
- ret = __mm_cid_get(mm);
- raw_spin_unlock(&mm->cid_lock);
- return ret;
+ pcpu_cid = this_cpu_ptr(mm->pcpu_cid);
+ cid = *pcpu_cid;
+ if (pcpu_cid_is_unset(cid)) {
+ raw_spin_lock(&mm->cid_lock);
+ cid = __mm_cid_get_locked(mm);
+ raw_spin_unlock(&mm->cid_lock);
+ *pcpu_cid = cid;
+ return cid;
+ }
+ return cid;
}
static inline void switch_mm_cid(struct task_struct *prev, struct task_struct *next)
{
if (prev->mm_cid_active) {
- if (next->mm_cid_active && next->mm == prev->mm) {
- /*
- * Context switch between threads in same mm, hand over
- * the mm_cid from prev to next.
- */
- next->mm_cid = prev->mm_cid;
- prev->mm_cid = -1;
- return;
- }
- mm_cid_put(prev->mm, prev->mm_cid);
+ mm_cid_put_lazy(prev->mm, prev->mm_cid);
prev->mm_cid = -1;
}
if (next->mm_cid_active)
@@ -3304,6 +3342,9 @@ static inline void switch_mm_cid(struct task_struct *prev, struct task_struct *n
#else
static inline void switch_mm_cid(struct task_struct *prev, struct task_struct *next) { }
+static inline void sched_mm_cid_migrate(struct rq *rq, struct task_struct *t, int new_cpu) { }
+static inline int sched_mm_cid_migrate_from(struct rq *src_rq, struct task_struct *t) { return 0; }
+static inline void sched_mm_cid_migrate_to(struct rq *src_rq, struct task_struct *t, int cid) { }
#endif
#endif /* _KERNEL_SCHED_SCHED_H */
--
2.25.1
On Thu, Mar 30, 2023 at 07:09:11PM -0400, Mathieu Desnoyers wrote:
> void sched_mm_cid_exit_signals(struct task_struct *t)
> {
> struct mm_struct *mm = t->mm;
> - unsigned long flags;
> + struct rq *rq = this_rq();
Got many below messages due to the above line:
[ 19.294089] BUG: using smp_processor_id() in preemptible [00000000] code: kworker/u449:0/1621
> + struct rq_flags rf;
>
> if (!mm)
> return;
> - local_irq_save(flags);
> + rq_lock_irqsave(rq, &rf);
> mm_cid_put(mm, t->mm_cid);
> t->mm_cid = -1;
> t->mm_cid_active = 0;
> - local_irq_restore(flags);
> + rq_unlock_irqrestore(rq, &rf);
> }
>
> void sched_mm_cid_before_execve(struct task_struct *t)
> {
> struct mm_struct *mm = t->mm;
> - unsigned long flags;
> + struct rq *rq = this_rq();
Also here;
> + struct rq_flags rf;
>
> if (!mm)
> return;
> - local_irq_save(flags);
> + rq_lock_irqsave(rq, &rf);
> mm_cid_put(mm, t->mm_cid);
> t->mm_cid = -1;
> t->mm_cid_active = 0;
> - local_irq_restore(flags);
> + rq_unlock_irqrestore(rq, &rf);
> }
>
> void sched_mm_cid_after_execve(struct task_struct *t)
> {
> struct mm_struct *mm = t->mm;
> - unsigned long flags;
> + struct rq *rq = this_rq();
And here.
> + struct rq_flags rf;
>
> if (!mm)
> return;
> - local_irq_save(flags);
> + rq_lock_irqsave(rq, &rf);
> t->mm_cid = mm_cid_get(mm);
> t->mm_cid_active = 1;
> - local_irq_restore(flags);
> + rq_unlock_irqrestore(rq, &rf);
> rseq_set_notify_resume(t);
> }
I used below diff to get rid of these messages without understanding the
purpose of these functions:
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f07b87d155bd..7194c29f3c91 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -11444,45 +11444,57 @@ void sched_mm_cid_migrate_to(struct rq *dst_rq, struct task_struct *t, int src_c
void sched_mm_cid_exit_signals(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
- struct rq *rq = this_rq();
struct rq_flags rf;
+ struct rq *rq;
if (!mm)
return;
+
+ preempt_disable();
+ rq = this_rq();
rq_lock_irqsave(rq, &rf);
mm_cid_put(mm, t->mm_cid);
t->mm_cid = -1;
t->mm_cid_active = 0;
rq_unlock_irqrestore(rq, &rf);
+ preempt_enable();
}
void sched_mm_cid_before_execve(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
- struct rq *rq = this_rq();
struct rq_flags rf;
+ struct rq *rq;
if (!mm)
return;
+
+ preempt_disable();
+ rq = this_rq();
rq_lock_irqsave(rq, &rf);
mm_cid_put(mm, t->mm_cid);
t->mm_cid = -1;
t->mm_cid_active = 0;
rq_unlock_irqrestore(rq, &rf);
+ preempt_enable();
}
void sched_mm_cid_after_execve(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
- struct rq *rq = this_rq();
struct rq_flags rf;
+ struct rq *rq;
if (!mm)
return;
+
+ preempt_disable();
+ rq = this_rq();
rq_lock_irqsave(rq, &rf);
t->mm_cid = mm_cid_get(mm);
t->mm_cid_active = 1;
rq_unlock_irqrestore(rq, &rf);
+ preempt_enable();
rseq_set_notify_resume(t);
}
--
2.34.1
On Thu, Mar 30, 2023 at 07:09:11PM -0400, Mathieu Desnoyers wrote:
> Keep track of the currently allocated mm_cid for each mm/cpu rather than
> freeing them immediately. This eliminates most atomic ops when context
> switching back and forth between threads belonging to different memory
> spaces in multi-threaded scenarios (many processes, each with many
> threads).
Good news, the lock contention is now gone and back to v6.2 level:
node0_0.profile: 0.07% 0.07% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node0_1.profile: 0.06% 0.06% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node0_2.profile: 0.09% 0.09% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node0_3.profile: 0.08% 0.08% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node0_4.profile: 0.09% 0.09% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node0_5.profile: 0.10% 0.10% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node0_6.profile: 0.10% 0.10% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node0_7.profile: 0.07% 0.07% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node0_8.profile: 0.08% 0.08% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node0_9.profile: 0.06% 0.06% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node1_0.profile: 0.41% 0.41% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node1_1.profile: 0.38% 0.38% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node1_2.profile: 0.44% 0.44% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node1_3.profile: 5.64% 5.64% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node1_4.profile: 6.08% 6.08% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node1_5.profile: 3.45% 3.45% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node1_6.profile: 2.09% 2.09% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node1_7.profile: 2.72% 2.72% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node1_8.profile: 0.16% 0.16% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
node1_9.profile: 0.15% 0.15% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
(those few profiles from node1's cpus that have more than 2% contention
are from thermal functions)
Tested-by: Aaron Lu <[email protected]> # lock contention part
On 2023-03-31 04:38, Aaron Lu wrote:
> On Thu, Mar 30, 2023 at 07:09:11PM -0400, Mathieu Desnoyers wrote:
>
>> void sched_mm_cid_exit_signals(struct task_struct *t)
>> {
>> struct mm_struct *mm = t->mm;
>> - unsigned long flags;
>> + struct rq *rq = this_rq();
>
> Got many below messages due to the above line:
>
> [ 19.294089] BUG: using smp_processor_id() in preemptible [00000000] code: kworker/u449:0/1621
>
>> + struct rq_flags rf;
>>
>> if (!mm)
>> return;
>> - local_irq_save(flags);
>> + rq_lock_irqsave(rq, &rf);
>> mm_cid_put(mm, t->mm_cid);
>> t->mm_cid = -1;
>> t->mm_cid_active = 0;
>> - local_irq_restore(flags);
>> + rq_unlock_irqrestore(rq, &rf);
>> }
>>
>> void sched_mm_cid_before_execve(struct task_struct *t)
>> {
>> struct mm_struct *mm = t->mm;
>> - unsigned long flags;
>> + struct rq *rq = this_rq();
>
> Also here;
>
>> + struct rq_flags rf;
>>
>> if (!mm)
>> return;
>> - local_irq_save(flags);
>> + rq_lock_irqsave(rq, &rf);
>> mm_cid_put(mm, t->mm_cid);
>> t->mm_cid = -1;
>> t->mm_cid_active = 0;
>> - local_irq_restore(flags);
>> + rq_unlock_irqrestore(rq, &rf);
>> }
>>
>> void sched_mm_cid_after_execve(struct task_struct *t)
>> {
>> struct mm_struct *mm = t->mm;
>> - unsigned long flags;
>> + struct rq *rq = this_rq();
>
> And here.
>
>> + struct rq_flags rf;
>>
>> if (!mm)
>> return;
>> - local_irq_save(flags);
>> + rq_lock_irqsave(rq, &rf);
>> t->mm_cid = mm_cid_get(mm);
>> t->mm_cid_active = 1;
>> - local_irq_restore(flags);
>> + rq_unlock_irqrestore(rq, &rf);
>> rseq_set_notify_resume(t);
>> }
>
> I used below diff to get rid of these messages without understanding the
> purpose of these functions:
I'll fold this fix into the next round, thanks!
Mathieu
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index f07b87d155bd..7194c29f3c91 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -11444,45 +11444,57 @@ void sched_mm_cid_migrate_to(struct rq *dst_rq, struct task_struct *t, int src_c
> void sched_mm_cid_exit_signals(struct task_struct *t)
> {
> struct mm_struct *mm = t->mm;
> - struct rq *rq = this_rq();
> struct rq_flags rf;
> + struct rq *rq;
>
> if (!mm)
> return;
> +
> + preempt_disable();
> + rq = this_rq();
> rq_lock_irqsave(rq, &rf);
> mm_cid_put(mm, t->mm_cid);
> t->mm_cid = -1;
> t->mm_cid_active = 0;
> rq_unlock_irqrestore(rq, &rf);
> + preempt_enable();
> }
>
> void sched_mm_cid_before_execve(struct task_struct *t)
> {
> struct mm_struct *mm = t->mm;
> - struct rq *rq = this_rq();
> struct rq_flags rf;
> + struct rq *rq;
>
> if (!mm)
> return;
> +
> + preempt_disable();
> + rq = this_rq();
> rq_lock_irqsave(rq, &rf);
> mm_cid_put(mm, t->mm_cid);
> t->mm_cid = -1;
> t->mm_cid_active = 0;
> rq_unlock_irqrestore(rq, &rf);
> + preempt_enable();
> }
>
> void sched_mm_cid_after_execve(struct task_struct *t)
> {
> struct mm_struct *mm = t->mm;
> - struct rq *rq = this_rq();
> struct rq_flags rf;
> + struct rq *rq;
>
> if (!mm)
> return;
> +
> + preempt_disable();
> + rq = this_rq();
> rq_lock_irqsave(rq, &rf);
> t->mm_cid = mm_cid_get(mm);
> t->mm_cid_active = 1;
> rq_unlock_irqrestore(rq, &rf);
> + preempt_enable();
> rseq_set_notify_resume(t);
> }
>
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
On 2023-03-31 04:52, Aaron Lu wrote:
> On Thu, Mar 30, 2023 at 07:09:11PM -0400, Mathieu Desnoyers wrote:
>> Keep track of the currently allocated mm_cid for each mm/cpu rather than
>> freeing them immediately. This eliminates most atomic ops when context
>> switching back and forth between threads belonging to different memory
>> spaces in multi-threaded scenarios (many processes, each with many
>> threads).
>
> Good news, the lock contention is now gone and back to v6.2 level:
Hi Aaron,
Can you please test the updated patch I've sent ? I have updated the
subject to make it clear that this is a fix for a performance regression,
improved comments, and it now passes more thorough testing. See:
https://lore.kernel.org/lkml/[email protected]/
Thanks,
Mathieu
>
> node0_0.profile: 0.07% 0.07% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node0_1.profile: 0.06% 0.06% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node0_2.profile: 0.09% 0.09% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node0_3.profile: 0.08% 0.08% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node0_4.profile: 0.09% 0.09% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node0_5.profile: 0.10% 0.10% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node0_6.profile: 0.10% 0.10% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node0_7.profile: 0.07% 0.07% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node0_8.profile: 0.08% 0.08% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node0_9.profile: 0.06% 0.06% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node1_0.profile: 0.41% 0.41% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node1_1.profile: 0.38% 0.38% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node1_2.profile: 0.44% 0.44% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node1_3.profile: 5.64% 5.64% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node1_4.profile: 6.08% 6.08% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node1_5.profile: 3.45% 3.45% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node1_6.profile: 2.09% 2.09% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node1_7.profile: 2.72% 2.72% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node1_8.profile: 0.16% 0.16% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> node1_9.profile: 0.15% 0.15% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath
> (those few profiles from node1's cpus that have more than 2% contention
> are from thermal functions)
>
> Tested-by: Aaron Lu <[email protected]> # lock contention part
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com