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authorBen Hutchings <bhutchings@solarflare.com>2011-01-19 11:03:25 +0000
committerDavid S. Miller <davem@davemloft.net>2011-01-24 14:51:56 -0800
commitc39649c331c70952700f99832b03f87e9d7f5b4b (patch)
tree19ba9cea5102595e42bcd043aa53eb666ea834fa /include/linux/cpu_rmap.h
parentc2df88cbb43c25db27fbbf94e92318bdad018f3e (diff)
downloadlwn-c39649c331c70952700f99832b03f87e9d7f5b4b.tar.gz
lwn-c39649c331c70952700f99832b03f87e9d7f5b4b.zip
lib: cpu_rmap: CPU affinity reverse-mapping
When initiating I/O on a multiqueue and multi-IRQ device, we may want to select a queue for which the response will be handled on the same or a nearby CPU. This requires a reverse-map of IRQ affinity. Add library functions to support a generic reverse-mapping from CPUs to objects with affinity and the specific case where the objects are IRQs. Signed-off-by: Ben Hutchings <bhutchings@solarflare.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/cpu_rmap.h')
-rw-r--r--include/linux/cpu_rmap.h73
1 files changed, 73 insertions, 0 deletions
diff --git a/include/linux/cpu_rmap.h b/include/linux/cpu_rmap.h
new file mode 100644
index 000000000000..473771a528c0
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+++ b/include/linux/cpu_rmap.h
@@ -0,0 +1,73 @@
+/*
+ * cpu_rmap.c: CPU affinity reverse-map support
+ * Copyright 2011 Solarflare Communications Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation, incorporated herein by reference.
+ */
+
+#include <linux/cpumask.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+
+/**
+ * struct cpu_rmap - CPU affinity reverse-map
+ * @size: Number of objects to be reverse-mapped
+ * @used: Number of objects added
+ * @obj: Pointer to array of object pointers
+ * @near: For each CPU, the index and distance to the nearest object,
+ * based on affinity masks
+ */
+struct cpu_rmap {
+ u16 size, used;
+ void **obj;
+ struct {
+ u16 index;
+ u16 dist;
+ } near[0];
+};
+#define CPU_RMAP_DIST_INF 0xffff
+
+extern struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags);
+
+/**
+ * free_cpu_rmap - free CPU affinity reverse-map
+ * @rmap: Reverse-map allocated with alloc_cpu_rmap(), or %NULL
+ */
+static inline void free_cpu_rmap(struct cpu_rmap *rmap)
+{
+ kfree(rmap);
+}
+
+extern int cpu_rmap_add(struct cpu_rmap *rmap, void *obj);
+extern int cpu_rmap_update(struct cpu_rmap *rmap, u16 index,
+ const struct cpumask *affinity);
+
+static inline u16 cpu_rmap_lookup_index(struct cpu_rmap *rmap, unsigned int cpu)
+{
+ return rmap->near[cpu].index;
+}
+
+static inline void *cpu_rmap_lookup_obj(struct cpu_rmap *rmap, unsigned int cpu)
+{
+ return rmap->obj[rmap->near[cpu].index];
+}
+
+#ifdef CONFIG_GENERIC_HARDIRQS
+
+/**
+ * alloc_irq_cpu_rmap - allocate CPU affinity reverse-map for IRQs
+ * @size: Number of objects to be mapped
+ *
+ * Must be called in process context.
+ */
+static inline struct cpu_rmap *alloc_irq_cpu_rmap(unsigned int size)
+{
+ return alloc_cpu_rmap(size, GFP_KERNEL);
+}
+extern void free_irq_cpu_rmap(struct cpu_rmap *rmap);
+
+extern int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq);
+
+#endif