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lib: cpu_rmap: CPU affinity reverse-mapping

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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>
This commit is contained in:
Ben Hutchings
2011-01-19 11:03:25 +00:00
committed by David S. Miller
parent c2df88cbb4
commit c39649c331
4 changed files with 348 additions and 0 deletions
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73
include/linux/cpu_rmap.h Normal file
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/*
* 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