[Xenomai-core] [RFC][PATCH 2/2] global CPU affinity control

[Xenomai-core] [RFC][PATCH 2/2] global CPU affinity control

[Jan Kiszka]

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This is version 4 of the /proc/xenomai/affinity feature. It has been
rebased on the reworked xnshadow_map code, now applying the default
affinity mask in a (hopefully) correct way also on shadow threads.

What has been said for the previous patch also applies here: test and
comment! Mathias, you asked for this feature, please let us know if it
fulfils your requirements.

Philippe, you were looking for documentation of this new behaviour.
Please let me know where you would like to see this. Surely in the
nucleus API, I guess. Anywhere else?

Jan

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---
 include/nucleus/pod.h    |    2 +
 ksrc/nucleus/intr.c      |    3 ++
 ksrc/nucleus/module.c    |   57 +++++++++++++++++++++++++++++++++++++++++++++++
 ksrc/nucleus/pod.c       |    6 +++-
 ksrc/nucleus/shadow.c    |    3 ++
 ksrc/skins/native/task.c |    3 ++
 6 files changed, 72 insertions(+), 2 deletions(-)

Index: xenomai/include/nucleus/pod.h
===================================================================
--- xenomai.orig/include/nucleus/pod.h
+++ xenomai/include/nucleus/pod.h
@@ -256,6 +256,8 @@ extern u_long nktickdef;
 
 extern char *nkmsgbuf;
 
+extern xnarch_cpumask_t nkaffinity;
+
 #define xnprintf(fmt,args...)  xnarch_printf(fmt , ##args)
 #define xnloginfo(fmt,args...) xnarch_loginfo(fmt , ##args)
 #define xnlogwarn(fmt,args...) xnarch_logwarn(fmt , ##args)
Index: xenomai/ksrc/nucleus/module.c
===================================================================
--- xenomai.orig/ksrc/nucleus/module.c
+++ xenomai/ksrc/nucleus/module.c
@@ -688,6 +688,59 @@ static int heap_read_proc(char *page,
 	return len;
 }
 
+static int affinity_read_proc(char *page,
+			      char **start,
+			      off_t off, int count, int *eof, void *data)
+{
+	unsigned long val = 0;
+	int len, cpu;
+
+	for (cpu = 0; cpu < sizeof(val) * 8; cpu++)
+		if (xnarch_cpu_isset(cpu, nkaffinity))
+			val |= (1 << cpu);
+
+	len = sprintf(page, "%08lx\n", val);
+	len -= off;
+	if (len <= off + count)
+		*eof = 1;
+	*start = page + off;
+	if (len > count)
+		len = count;
+	if (len < 0)
+		len = 0;
+
+	return len;
+}
+
+static int affinity_write_proc(struct file *file,
+			       const char __user * buffer,
+			       unsigned long count, void *data)
+{
+	char *end, buf[16];
+	unsigned long val;
+	xnarch_cpumask_t new_affinity;
+	int n, cpu;
+
+	n = count > sizeof(buf) - 1 ? sizeof(buf) - 1 : count;
+
+	if (copy_from_user(buf, buffer, n))
+		return -EFAULT;
+
+	buf[n] = '\0';
+	val = simple_strtol(buf, &end, 0);
+
+	if (*end != '\0' && !isspace(*end))
+		return -EINVAL;
+
+	xnarch_cpus_clear(new_affinity);
+	for (cpu = 0; cpu < sizeof(val) * 8; cpu++, val >>= 1)
+		if (val & 1)
+			xnarch_cpu_set(cpu, new_affinity);
+	nkaffinity = new_affinity;
+
+	return count;
+}
+
 static struct proc_dir_entry *add_proc_leaf(const char *name,
 					    read_proc_t rdproc,
 					    write_proc_t wrproc,
@@ -760,6 +813,9 @@ void xnpod_init_proc(void)
 
 	add_proc_leaf("heap", &heap_read_proc, NULL, NULL, rthal_proc_root);
 
+	add_proc_leaf("affinity", &affinity_read_proc, &affinity_write_proc,
+		      NULL, rthal_proc_root);
+
 #ifdef CONFIG_XENO_OPT_PERVASIVE
 	iface_proc_root =
 	    create_proc_entry("interfaces", S_IFDIR, rthal_proc_root);
@@ -778,6 +834,7 @@ void xnpod_delete_proc(void)
 
 	remove_proc_entry("interfaces", rthal_proc_root);
 #endif /* CONFIG_XENO_OPT_PERVASIVE */
+	remove_proc_entry("affinity", rthal_proc_root);
 	remove_proc_entry("heap", rthal_proc_root);
 	remove_proc_entry("irq", rthal_proc_root);
 	remove_proc_entry("timer", rthal_proc_root);
Index: xenomai/ksrc/nucleus/pod.c
===================================================================
--- xenomai.orig/ksrc/nucleus/pod.c
+++ xenomai/ksrc/nucleus/pod.c
@@ -70,6 +70,8 @@ MODULE_PARM_DESC(tick_arg, "Fixed clock 
 
 char *nkmsgbuf = NULL;
 
+xnarch_cpumask_t nkaffinity = XNPOD_ALL_CPUS;
+
 const char *xnpod_fatal_helper(const char *format, ...)
 {
 	const unsigned nr_cpus = xnarch_num_online_cpus();
@@ -909,8 +911,8 @@ int xnpod_start_thread(xnthread_t *threa
 	if (!testbits(thread->status, XNDORMANT))
 		return -EBUSY;
 
-	if (xnarch_cpus_empty(affinity))
-		affinity = XNARCH_CPU_MASK_ALL;
+	if (xnarch_cpus_equal(affinity, XNPOD_ALL_CPUS))
+		affinity = nkaffinity;
 
 	xnlock_get_irqsave(&nklock, s);
 
Index: xenomai/ksrc/nucleus/shadow.c
===================================================================
--- xenomai.orig/ksrc/nucleus/shadow.c
+++ xenomai/ksrc/nucleus/shadow.c
@@ -847,6 +847,9 @@ int xnshadow_map(xnthread_t *thread, xnc
 	xnshadow_thrptd(current) = thread;
 	xnpod_suspend_thread(thread, XNRELAX, XN_INFINITE, NULL);
 
+	if (xnarch_cpus_equal(affinity, XNPOD_ALL_CPUS))
+		affinity = nkaffinity;
+
 	/* Apply provided cpumask on the Linux task. */
 	set_cpus_allowed(current, affinity);
 
Index: xenomai/ksrc/skins/native/task.c
===================================================================
--- xenomai.orig/ksrc/skins/native/task.c
+++ xenomai/ksrc/skins/native/task.c
@@ -255,6 +255,9 @@ int rt_task_create(RT_TASK *task,
 		if (cpumask & 1)
 			xnarch_cpu_set(cpu, task->affinity);
 
+	if (xnarch_cpus_empty(task->affinity))
+		task->affinity = XNPOD_ALL_CPUS;
+
 #ifdef CONFIG_XENO_OPT_NATIVE_MPS
 	xnsynch_init(&task->mrecv, XNSYNCH_FIFO);
 	xnsynch_init(&task->msendq, XNSYNCH_PRIO | XNSYNCH_PIP);
Index: xenomai/ksrc/nucleus/intr.c
===================================================================
--- xenomai.orig/ksrc/nucleus/intr.c
+++ xenomai/ksrc/nucleus/intr.c
@@ -626,6 +626,9 @@ int xnintr_attach(xnintr_t *intr, void *
 
 	xnlock_get_irqsave(&intrlock, s);
 
+#ifdef CONFIG_SMP
+	xnarch_set_irq_affinity(intr->irq, nkaffinity);
+#endif /* CONFIG_SMP */
 	err = xnintr_irq_attach(intr);
 
 	xnlock_put_irqrestore(&intrlock, s);

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[Xenomai-core] Re: [RFC][PATCH 2/2] global CPU affinity control

[Gilles Chanteperdrix]

Jan Kiszka wrote:
> This is version 4 of the /proc/xenomai/affinity feature. It has been
> rebased on the reworked xnshadow_map code, now applying the default
> affinity mask in a (hopefully) correct way also on shadow threads.
> 
> What has been said for the previous patch also applies here: test and
> comment! Mathias, you asked for this feature, please let us know if it
> fulfils your requirements.
> 
> Philippe, you were looking for documentation of this new behaviour.
> Please let me know where you would like to see this. Surely in the
> nucleus API, I guess. Anywhere else?
> 
> Jan
> 
> 
> ------------------------------------------------------------------------
> (...)
> @@ -909,8 +911,8 @@ int xnpod_start_thread(xnthread_t *threa
>  	if (!testbits(thread->status, XNDORMANT))
>  		return -EBUSY;
>  
> -	if (xnarch_cpus_empty(affinity))
> -		affinity = XNARCH_CPU_MASK_ALL;
> +	if (xnarch_cpus_equal(affinity, XNPOD_ALL_CPUS))
> +		affinity = nkaffinity;

Should not this be:
	if (xnarch_cpus_empty(affinity))
		affinity = XNARCH_CPU_MASK_ALL;
	xnarch_cpus_and(affinity, affinity, nkaffinity);
	if (xnarch_cpus_empty(affinity))
		return -EINVAL;

so that no thread could escape the rule imposed by nkaffinity.

-- 
                                                 Gilles Chanteperdrix

Re: [Xenomai-core] Re: [RFC][PATCH 2/2] global CPU affinity control

[Jan Kiszka]

Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> This is version 4 of the /proc/xenomai/affinity feature. It has been
>> rebased on the reworked xnshadow_map code, now applying the default
>> affinity mask in a (hopefully) correct way also on shadow threads.
>>
>> What has been said for the previous patch also applies here: test and
>> comment! Mathias, you asked for this feature, please let us know if it
>> fulfils your requirements.
>>
>> Philippe, you were looking for documentation of this new behaviour.
>> Please let me know where you would like to see this. Surely in the
>> nucleus API, I guess. Anywhere else?
>>
>> Jan
>>
>>
>> ------------------------------------------------------------------------
>> (...)
>> @@ -909,8 +911,8 @@ int xnpod_start_thread(xnthread_t *threa
>>  	if (!testbits(thread->status, XNDORMANT))
>>  		return -EBUSY;
>>  
>> -	if (xnarch_cpus_empty(affinity))
>> -		affinity = XNARCH_CPU_MASK_ALL;
>> +	if (xnarch_cpus_equal(affinity, XNPOD_ALL_CPUS))
>> +		affinity = nkaffinity;
> 
> Should not this be:
> 	if (xnarch_cpus_empty(affinity))
> 		affinity = XNARCH_CPU_MASK_ALL;
> 	xnarch_cpus_and(affinity, affinity, nkaffinity);
> 	if (xnarch_cpus_empty(affinity))
> 		return -EINVAL;
> 
> so that no thread could escape the rule imposed by nkaffinity.
> 

Nope, that's intentional (forgot to repeat this fact, was explained
earlier): Users can always override nkaffinity by their own mask. Only
the "I-don't-care" XNPOD_ALL_CPUS activates this new selection mechanism.

Jan

[Xenomai-core] Re: [RFC][PATCH 2/2] global CPU affinity control

[Jan Kiszka]

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M. Koehrer wrote:
> Hi Jan,
> 
> thanks for the patch!
> This looks fine to me. This allows me easily to set the affinity of the xenomai tasks.
> 
> As far as I understood, I have to specify XNPOD_ALL_CPUS as parameter
> at rt_task_create() to use this feature.

...or an empty mask, both works.

> What about the rtnet internal (kernel) task (created via RTDM)? 
> Will it use this affinity as well or do I have to "force" rtnet somehow to use the
> "global" xenomai affinity?

Yes, it affects any Xenomai thread that doesn't specify an explicit
mask. And it forces all IRQs that are newly attached to the specified
affinity. You should be able to watch this under
/proc/irq/<n>/smp_affinity. That avoids e.g. that the NIC IRQ pops up on
CPU 0 but has to wake up the stack manager on CPU 1.

Jan


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Re: [Xenomai-core] Re: [RFC][PATCH 2/2] global CPU affinity control

[Gilles Chanteperdrix]

Jan Kiszka wrote:
> Nope, that's intentional (forgot to repeat this fact, was explained
> earlier): Users can always override nkaffinity by their own mask. Only
> the "I-don't-care" XNPOD_ALL_CPUS activates this new selection mechanism.

Ok. But there is still something wrong: if the affinity is empty, it
will remain empty whereas it was replaced by XNARCH_CPU_MASK_ALL in the
current version.

-- 
                                                 Gilles Chanteperdrix

Re: [Xenomai-core] Re: [RFC][PATCH 2/2] global CPU affinity control

[Jan Kiszka]

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Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> Nope, that's intentional (forgot to repeat this fact, was explained
>> earlier): Users can always override nkaffinity by their own mask. Only
>> the "I-don't-care" XNPOD_ALL_CPUS activates this new selection mechanism.
> 
> Ok. But there is still something wrong: if the affinity is empty, it
> will remain empty whereas it was replaced by XNARCH_CPU_MASK_ALL in the
> current version.
> 

The policy is that no skin should invoke xnshadow_map or
xnpod_start_thread with an empty mask anymore. So far only the native
skin made use of this, and that is changed by the patch.



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Re: [Xenomai-core] [RFC][PATCH 2/2] global CPU affinity control

[Jan Kiszka]

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Version 5 is basically a rebase over the first patch of this series. It
also enforces that cpus_allowed of a shadow thread only contains a
single CPU.

Only compile-tested.

Jan

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---
 include/nucleus/pod.h    |    2 +
 ksrc/nucleus/intr.c      |    3 ++
 ksrc/nucleus/module.c    |   57 +++++++++++++++++++++++++++++++++++++++++++++++
 ksrc/nucleus/pod.c       |    6 +++-
 ksrc/nucleus/shadow.c    |   12 ++++++---
 ksrc/skins/native/task.c |    3 ++
 6 files changed, 77 insertions(+), 6 deletions(-)

Index: xenomai/include/nucleus/pod.h
===================================================================
--- xenomai.orig/include/nucleus/pod.h
+++ xenomai/include/nucleus/pod.h
@@ -253,6 +253,8 @@ extern u_long nktickdef;
 
 extern char *nkmsgbuf;
 
+extern xnarch_cpumask_t nkaffinity;
+
 #define xnprintf(fmt,args...)  xnarch_printf(fmt , ##args)
 #define xnloginfo(fmt,args...) xnarch_loginfo(fmt , ##args)
 #define xnlogwarn(fmt,args...) xnarch_logwarn(fmt , ##args)
Index: xenomai/ksrc/nucleus/module.c
===================================================================
--- xenomai.orig/ksrc/nucleus/module.c
+++ xenomai/ksrc/nucleus/module.c
@@ -688,6 +688,59 @@ static int heap_read_proc(char *page,
 	return len;
 }
 
+static int affinity_read_proc(char *page,
+			      char **start,
+			      off_t off, int count, int *eof, void *data)
+{
+	unsigned long val = 0;
+	int len, cpu;
+
+	for (cpu = 0; cpu < sizeof(val) * 8; cpu++)
+		if (xnarch_cpu_isset(cpu, nkaffinity))
+			val |= (1 << cpu);
+
+	len = sprintf(page, "%08lx\n", val);
+	len -= off;
+	if (len <= off + count)
+		*eof = 1;
+	*start = page + off;
+	if (len > count)
+		len = count;
+	if (len < 0)
+		len = 0;
+
+	return len;
+}
+
+static int affinity_write_proc(struct file *file,
+			       const char __user * buffer,
+			       unsigned long count, void *data)
+{
+	char *end, buf[16];
+	unsigned long val;
+	xnarch_cpumask_t new_affinity;
+	int n, cpu;
+
+	n = count > sizeof(buf) - 1 ? sizeof(buf) - 1 : count;
+
+	if (copy_from_user(buf, buffer, n))
+		return -EFAULT;
+
+	buf[n] = '\0';
+	val = simple_strtol(buf, &end, 0);
+
+	if (*end != '\0' && !isspace(*end))
+		return -EINVAL;
+
+	xnarch_cpus_clear(new_affinity);
+	for (cpu = 0; cpu < sizeof(val) * 8; cpu++, val >>= 1)
+		if (val & 1)
+			xnarch_cpu_set(cpu, new_affinity);
+	nkaffinity = new_affinity;
+
+	return count;
+}
+
 static struct proc_dir_entry *add_proc_leaf(const char *name,
 					    read_proc_t rdproc,
 					    write_proc_t wrproc,
@@ -760,6 +813,9 @@ void xnpod_init_proc(void)
 
 	add_proc_leaf("heap", &heap_read_proc, NULL, NULL, rthal_proc_root);
 
+	add_proc_leaf("affinity", &affinity_read_proc, &affinity_write_proc,
+		      NULL, rthal_proc_root);
+
 #ifdef CONFIG_XENO_OPT_PERVASIVE
 	iface_proc_root =
 	    create_proc_entry("interfaces", S_IFDIR, rthal_proc_root);
@@ -778,6 +834,7 @@ void xnpod_delete_proc(void)
 
 	remove_proc_entry("interfaces", rthal_proc_root);
 #endif /* CONFIG_XENO_OPT_PERVASIVE */
+	remove_proc_entry("affinity", rthal_proc_root);
 	remove_proc_entry("heap", rthal_proc_root);
 	remove_proc_entry("irq", rthal_proc_root);
 	remove_proc_entry("timer", rthal_proc_root);
Index: xenomai/ksrc/nucleus/pod.c
===================================================================
--- xenomai.orig/ksrc/nucleus/pod.c
+++ xenomai/ksrc/nucleus/pod.c
@@ -70,6 +70,8 @@ MODULE_PARM_DESC(tick_arg, "Fixed clock 
 
 char *nkmsgbuf = NULL;
 
+xnarch_cpumask_t nkaffinity = XNPOD_ALL_CPUS;
+
 const char *xnpod_fatal_helper(const char *format, ...)
 {
 	const unsigned nr_cpus = xnarch_num_online_cpus();
@@ -909,8 +911,8 @@ int xnpod_start_thread(xnthread_t *threa
 	if (!testbits(thread->status, XNDORMANT))
 		return -EBUSY;
 
-	if (xnarch_cpus_empty(affinity))
-		affinity = XNARCH_CPU_MASK_ALL;
+	if (xnarch_cpus_equal(affinity, XNPOD_ALL_CPUS))
+		affinity = nkaffinity;
 
 	xnlock_get_irqsave(&nklock, s);
 
Index: xenomai/ksrc/skins/native/task.c
===================================================================
--- xenomai.orig/ksrc/skins/native/task.c
+++ xenomai/ksrc/skins/native/task.c
@@ -255,6 +255,9 @@ int rt_task_create(RT_TASK *task,
 		if (cpumask & 1)
 			xnarch_cpu_set(cpu, task->affinity);
 
+	if (xnarch_cpus_empty(task->affinity))
+		task->affinity = XNPOD_ALL_CPUS;
+
 #ifdef CONFIG_XENO_OPT_NATIVE_MPS
 	xnsynch_init(&task->mrecv, XNSYNCH_FIFO);
 	xnsynch_init(&task->msendq, XNSYNCH_PRIO | XNSYNCH_PIP);
Index: xenomai/ksrc/nucleus/intr.c
===================================================================
--- xenomai.orig/ksrc/nucleus/intr.c
+++ xenomai/ksrc/nucleus/intr.c
@@ -626,6 +626,9 @@ int xnintr_attach(xnintr_t *intr, void *
 
 	xnlock_get_irqsave(&intrlock, s);
 
+#ifdef CONFIG_SMP
+	xnarch_set_irq_affinity(intr->irq, nkaffinity);
+#endif /* CONFIG_SMP */
 	err = xnintr_irq_attach(intr);
 
 	xnlock_put_irqrestore(&intrlock, s);
Index: xenomai/ksrc/nucleus/shadow.c
===================================================================
--- xenomai.orig/ksrc/nucleus/shadow.c
+++ xenomai/ksrc/nucleus/shadow.c
@@ -797,7 +797,7 @@ int xnshadow_map(xnthread_t *thread, xnc
 {
 	xnarch_cpumask_t affinity;
 	unsigned muxid, magic;
-	int mode, prio, err;
+	int mode, prio, err, cpu;
 
 	/* Increment the interface reference count. */
 	magic = xnthread_get_magic(thread);
@@ -843,9 +843,13 @@ int xnshadow_map(xnthread_t *thread, xnc
 	xnshadow_thrptd(current) = thread;
 	xnpod_suspend_thread(thread, XNRELAX, XN_INFINITE, NULL);
 
-	/* Restrict affinity to a single CPU of the current set */
-	affinity = xnarch_cpumask_of_cpu(
-		xnarch_first_cpu(current->cpus_allowed));
+	/* Restrict affinity to a single CPU of nkaffinity or
+	   the current set. */
+	if (xnarch_cpus_equal(current->cpus_allowed, XNPOD_ALL_CPUS))
+		cpu = xnarch_first_cpu(nkaffinity);
+	else
+		cpu = xnarch_first_cpu(current->cpus_allowed);
+	affinity = xnarch_cpumask_of_cpu(cpu);
 	set_cpus_allowed(current, affinity);
 
 	if (u_completion) {

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