sparse irq_desc[] array: core kernel and x86 changes
Impact: new feature
Problem on distro kernels: irq_desc[NR_IRQS] takes megabytes of RAM with
NR_CPUS set to large values. The goal is to be able to scale up to much
larger NR_IRQS value without impacting the (important) common case.
To solve this, we generalize irq_desc[NR_IRQS] to an (optional) array of
irq_desc pointers.
When CONFIG_SPARSE_IRQ=y is used, we use kzalloc_node to get irq_desc,
this also makes the IRQ descriptors NUMA-local (to the site that calls
request_irq()).
This gets rid of the irq_cfg[] static array on x86 as well: irq_cfg now
uses desc->chip_data for x86 to store irq_cfg.
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 1e3b934..2924faa 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -141,8 +141,12 @@
int i;
/* By default all event channels notify CPU#0. */
- for_each_irq_desc(i, desc)
+ for_each_irq_desc(i, desc) {
+ if (!desc)
+ continue;
+
desc->affinity = cpumask_of_cpu(0);
+ }
#endif
memset(cpu_evtchn, 0, sizeof(cpu_evtchn));
@@ -231,7 +235,7 @@
int irq;
/* Only allocate from dynirq range */
- for_each_irq_nr(irq)
+ for (irq = 0; irq < nr_irqs; irq++)
if (irq_bindcount[irq] == 0)
break;
@@ -792,7 +796,7 @@
mask_evtchn(evtchn);
/* No IRQ <-> event-channel mappings. */
- for_each_irq_nr(irq)
+ for (irq = 0; irq < nr_irqs; irq++)
irq_info[irq].evtchn = 0; /* zap event-channel binding */
for (evtchn = 0; evtchn < NR_EVENT_CHANNELS; evtchn++)
@@ -824,7 +828,7 @@
mask_evtchn(i);
/* Dynamic IRQ space is currently unbound. Zero the refcnts. */
- for_each_irq_nr(i)
+ for (i = 0; i < nr_irqs; i++)
irq_bindcount[i] = 0;
irq_ctx_init(smp_processor_id());