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Message-ID: <ZHjf3Y99VuC51Ipr@tpad>
Date: Thu, 1 Jun 2023 15:13:49 -0300
From: Marcelo Tosatti <mtosatti@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Michal Hocko <mhocko@...e.com>
Cc: Christoph Lameter <cl@...ux.com>,
Aaron Tomlin <atomlin@...mlin.com>,
Frederic Weisbecker <frederic@...nel.org>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Vlastimil Babka <vbabka@...e.cz>,
Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 3/4] workqueue: add schedule_on_each_cpumask helper
On Tue, May 30, 2023 at 01:09:47PM -0700, Andrew Morton wrote:
> On Tue, 30 May 2023 11:52:37 -0300 Marcelo Tosatti <mtosatti@...hat.com> wrote:
>
> > Add a schedule_on_each_cpumask function, equivalent to
> > schedule_on_each_cpu but accepting a cpumask to operate.
> >
> > Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
> >
> > ---
> >
> > Index: linux-vmstat-remote/kernel/workqueue.c
> > ===================================================================
> > --- linux-vmstat-remote.orig/kernel/workqueue.c
> > +++ linux-vmstat-remote/kernel/workqueue.c
> > @@ -3455,6 +3455,56 @@ int schedule_on_each_cpu(work_func_t fun
> > return 0;
> > }
> >
> > +
> > +/**
> > + * schedule_on_each_cpumask - execute a function synchronously on each
> > + * CPU in "cpumask", for those which are online.
> > + *
> > + * @func: the function to call
> > + * @mask: the CPUs which to call function on
> > + *
> > + * schedule_on_each_cpu() executes @func on each specified CPU that is online,
> > + * using the system workqueue and blocks until all such CPUs have completed.
> > + * schedule_on_each_cpu() is very slow.
> > + *
> > + * Return:
> > + * 0 on success, -errno on failure.
> > + */
> > +int schedule_on_each_cpumask(work_func_t func, cpumask_t *cpumask)
> > +{
> > + int cpu;
> > + struct work_struct __percpu *works;
> > + cpumask_var_t effmask;
> > +
> > + works = alloc_percpu(struct work_struct);
> > + if (!works)
> > + return -ENOMEM;
> > +
> > + if (!alloc_cpumask_var(&effmask, GFP_KERNEL)) {
> > + free_percpu(works);
> > + return -ENOMEM;
> > + }
> > +
> > + cpumask_and(effmask, cpumask, cpu_online_mask);
> > +
> > + cpus_read_lock();
> > +
> > + for_each_cpu(cpu, effmask) {
>
> Should we check here that the cpu is still online?
>
> > + struct work_struct *work = per_cpu_ptr(works, cpu);
> > +
> > + INIT_WORK(work, func);
> > + schedule_work_on(cpu, work);
> > + }
> > +
> > + for_each_cpu(cpu, effmask)
> > + flush_work(per_cpu_ptr(works, cpu));
> > +
> > + cpus_read_unlock();
> > + free_percpu(works);
> > + free_cpumask_var(effmask);
> > + return 0;
> > +}
> > +
> > /**
> > * execute_in_process_context - reliably execute the routine with user context
> > * @fn: the function to execute
> > --- linux-vmstat-remote.orig/include/linux/workqueue.h
> > +++ linux-vmstat-remote/include/linux/workqueue.h
> > @@ -450,6 +450,7 @@ extern void __flush_workqueue(struct wor
> > extern void drain_workqueue(struct workqueue_struct *wq);
> >
> > extern int schedule_on_each_cpu(work_func_t func);
> > +extern int schedule_on_each_cpumask(work_func_t func, cpumask_t *cpumask);
>
> May as well make schedule_on_each_cpu() call
> schedule_on_each_cpumask()? Save a bit of text, and they're hardly
> performance-critical to that extent.
Agree, will wait for Michal's review before resending -v2.
workqueue: add schedule_on_each_cpumask helper
Add a schedule_on_each_cpumask function, equivalent to
schedule_on_each_cpu but accepting a cpumask to operate.
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
---
v2: - cpu_online_mask reference should happen with cpus_read_lock held (Andrew Morton)
- have schedule_on_each_cpu call _cpumask variant (Andrew Morton)
Index: linux-vmstat-remote/kernel/workqueue.c
===================================================================
--- linux-vmstat-remote.orig/kernel/workqueue.c
+++ linux-vmstat-remote/kernel/workqueue.c
@@ -3431,27 +3431,56 @@ EXPORT_SYMBOL(cancel_delayed_work_sync);
*/
int schedule_on_each_cpu(work_func_t func)
{
+ return schedule_on_each_cpumask(func, cpu_possible_mask);
+}
+
+
+/**
+ * schedule_on_each_cpumask - execute a function synchronously on each
+ * CPU in "cpumask", for those which are online.
+ *
+ * @func: the function to call
+ * @mask: the CPUs which to call function on
+ *
+ * schedule_on_each_cpu() executes @func on each specified CPU that is online,
+ * using the system workqueue and blocks until all such CPUs have completed.
+ * schedule_on_each_cpu() is very slow.
+ *
+ * Return:
+ * 0 on success, -errno on failure.
+ */
+int schedule_on_each_cpumask(work_func_t func, cpumask_t *cpumask)
+{
int cpu;
struct work_struct __percpu *works;
+ cpumask_var_t effmask;
works = alloc_percpu(struct work_struct);
if (!works)
return -ENOMEM;
+ if (!alloc_cpumask_var(&effmask, GFP_KERNEL)) {
+ free_percpu(works);
+ return -ENOMEM;
+ }
+
cpus_read_lock();
- for_each_online_cpu(cpu) {
+ cpumask_and(effmask, cpumask, cpu_online_mask);
+
+ for_each_cpu(cpu, effmask) {
struct work_struct *work = per_cpu_ptr(works, cpu);
INIT_WORK(work, func);
schedule_work_on(cpu, work);
}
- for_each_online_cpu(cpu)
+ for_each_cpu(cpu, effmask)
flush_work(per_cpu_ptr(works, cpu));
cpus_read_unlock();
free_percpu(works);
+ free_cpumask_var(effmask);
return 0;
}
Index: linux-vmstat-remote/include/linux/workqueue.h
===================================================================
--- linux-vmstat-remote.orig/include/linux/workqueue.h
+++ linux-vmstat-remote/include/linux/workqueue.h
@@ -450,6 +450,7 @@ extern void __flush_workqueue(struct wor
extern void drain_workqueue(struct workqueue_struct *wq);
extern int schedule_on_each_cpu(work_func_t func);
+extern int schedule_on_each_cpumask(work_func_t func, cpumask_t *cpumask);
int execute_in_process_context(work_func_t fn, struct execute_work *);
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