From 72dba584b695d8bc8c1a50ed54ad4cba7c62314d Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 14 Jun 2007 03:45:13 +0900 Subject: ida: implement idr based id allocator Implement idr based id allocator. ida is used the same way idr is used but lacks id -> ptr translation and thus consumes much less memory. struct ida_bitmap is attached as leaf nodes to idr tree which is managed by the idr code. Each ida_bitmap is 128bytes long and contains slightly less than a thousand slots. ida is more aggressive with releasing extra resources acquired using ida_pre_get(). After every successful id allocation, ida frees one reserved idr_layer if possible. Reserved ida_bitmap is not freed automatically but only one ida_bitmap is reserved and it's almost always used right away. Under most circumstances, ida won't hold on to memory for too long which isn't actively used. Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- include/linux/idr.h | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) (limited to 'include/linux/idr.h') diff --git a/include/linux/idr.h b/include/linux/idr.h index 8268034..915572f 100644 --- a/include/linux/idr.h +++ b/include/linux/idr.h @@ -83,4 +83,33 @@ void idr_remove(struct idr *idp, int id); void idr_destroy(struct idr *idp); void idr_init(struct idr *idp); + +/* + * IDA - IDR based id allocator, use when translation from id to + * pointer isn't necessary. + */ +#define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */ +#define IDA_BITMAP_LONGS (128 / sizeof(long) - 1) +#define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8) + +struct ida_bitmap { + long nr_busy; + unsigned long bitmap[IDA_BITMAP_LONGS]; +}; + +struct ida { + struct idr idr; + struct ida_bitmap *free_bitmap; +}; + +#define IDA_INIT(name) { .idr = IDR_INIT(name), .free_bitmap = NULL, } +#define DEFINE_IDA(name) struct ida name = IDA_INIT(name) + +int ida_pre_get(struct ida *ida, gfp_t gfp_mask); +int ida_get_new_above(struct ida *ida, int starting_id, int *p_id); +int ida_get_new(struct ida *ida, int *p_id); +void ida_remove(struct ida *ida, int id); +void ida_destroy(struct ida *ida); +void ida_init(struct ida *ida); + #endif /* __IDR_H__ */ -- cgit v1.1