DPDK: Data Plane Development Kit

18.02.0-rc0
rte_bitmap.h File Reference
#include <string.h>
#include <rte_common.h>
#include <rte_debug.h>
#include <rte_memory.h>
#include <rte_branch_prediction.h>
#include <rte_prefetch.h>

Go to the source code of this file.

Data Structures

struct  rte_bitmap

Functions

static uint32_t rte_bitmap_get_memory_footprint (uint32_t n_bits)
static struct rte_bitmaprte_bitmap_init (uint32_t n_bits, uint8_t *mem, uint32_t mem_size)
static int rte_bitmap_free (struct rte_bitmap *bmp)
static void rte_bitmap_reset (struct rte_bitmap *bmp)
static void rte_bitmap_prefetch0 (struct rte_bitmap *bmp, uint32_t pos)
static uint64_t rte_bitmap_get (struct rte_bitmap *bmp, uint32_t pos)
static void rte_bitmap_set (struct rte_bitmap *bmp, uint32_t pos)
static void rte_bitmap_set_slab (struct rte_bitmap *bmp, uint32_t pos, uint64_t slab)
static void rte_bitmap_clear (struct rte_bitmap *bmp, uint32_t pos)
static int rte_bitmap_scan (struct rte_bitmap *bmp, uint32_t *pos, uint64_t *slab)

Detailed Description

RTE Bitmap

The bitmap component provides a mechanism to manage large arrays of bits through bit get/set/clear and bit array scan operations.

The bitmap scan operation is optimized for 64-bit CPUs using 64/128 byte cache lines. The bitmap is hierarchically organized using two arrays (array1 and array2), with each bit in array1 being associated with a full cache line (512/1024 bits) of bitmap bits, which are stored in array2: the bit in array1 is set only when there is at least one bit set within its associated array2 bits, otherwise the bit in array1 is cleared. The read and write operations for array1 and array2 are always done in slabs of 64 bits.

This bitmap is not thread safe. For lock free operation on a specific bitmap instance, a single writer thread performing bit set/clear operations is allowed, only the writer thread can do bitmap scan operations, while there can be several reader threads performing bit get operations in parallel with the writer thread. When the use of locking primitives is acceptable, the serialization of the bit set/clear and bitmap scan operations needs to be enforced by the caller, while the bit get operation does not require locking the bitmap.

Definition in file rte_bitmap.h.

Function Documentation

static uint32_t rte_bitmap_get_memory_footprint ( uint32_t  n_bits)
inlinestatic

Bitmap memory footprint calculation

Parameters
n_bitsNumber of bits in the bitmap
Returns
Bitmap memory footprint measured in bytes on success, 0 on error

Definition at line 217 of file rte_bitmap.h.

static struct rte_bitmap* rte_bitmap_init ( uint32_t  n_bits,
uint8_t *  mem,
uint32_t  mem_size 
)
staticread

Bitmap initialization

Parameters
mem_sizeMinimum expected size of bitmap.
memBase address of array1 and array2.
n_bitsNumber of pre-allocated bits in array2. Must be non-zero and multiple of 512.
Returns
Handle to bitmap instance.

Definition at line 239 of file rte_bitmap.h.

static int rte_bitmap_free ( struct rte_bitmap bmp)
inlinestatic

Bitmap free

Parameters
bmpHandle to bitmap instance
Returns
0 upon success, error code otherwise

Definition at line 284 of file rte_bitmap.h.

static void rte_bitmap_reset ( struct rte_bitmap bmp)
inlinestatic

Bitmap reset

Parameters
bmpHandle to bitmap instance

Definition at line 301 of file rte_bitmap.h.

static void rte_bitmap_prefetch0 ( struct rte_bitmap bmp,
uint32_t  pos 
)
inlinestatic

Bitmap location prefetch into CPU L1 cache

Parameters
bmpHandle to bitmap instance
posBit position
Returns
0 upon success, error code otherwise

Definition at line 319 of file rte_bitmap.h.

static uint64_t rte_bitmap_get ( struct rte_bitmap bmp,
uint32_t  pos 
)
inlinestatic

Bitmap bit get

Parameters
bmpHandle to bitmap instance
posBit position
Returns
0 when bit is cleared, non-zero when bit is set

Definition at line 340 of file rte_bitmap.h.

static void rte_bitmap_set ( struct rte_bitmap bmp,
uint32_t  pos 
)
inlinestatic

Bitmap bit set

Parameters
bmpHandle to bitmap instance
posBit position

Definition at line 360 of file rte_bitmap.h.

static void rte_bitmap_set_slab ( struct rte_bitmap bmp,
uint32_t  pos,
uint64_t  slab 
)
inlinestatic

Bitmap slab set

Parameters
bmpHandle to bitmap instance
posBit position identifying the array2 slab
slabValue to be assigned to the 64-bit slab in array2

Definition at line 388 of file rte_bitmap.h.

static void rte_bitmap_clear ( struct rte_bitmap bmp,
uint32_t  pos 
)
inlinestatic

Bitmap bit clear

Parameters
bmpHandle to bitmap instance
posBit position

Definition at line 428 of file rte_bitmap.h.

static int rte_bitmap_scan ( struct rte_bitmap bmp,
uint32_t *  pos,
uint64_t *  slab 
)
inlinestatic

Bitmap scan (with automatic wrap-around)

Parameters
bmpHandle to bitmap instance
posWhen function call returns 1, pos contains the position of the next set bit, otherwise not modified
slabWhen function call returns 1, slab contains the value of the entire 64-bit slab where the bit indicated by pos is located. Slabs are always 64-bit aligned, so the position of the first bit of the slab (this bit is not necessarily set) is pos / 64. Once a slab has been returned by the bitmap scan operation, the internal pointers of the bitmap are updated to point after this slab, so the same slab will not be returned again if it contains more than one bit which is set. When function call returns 0, slab is not modified.
Returns
0 if there is no bit set in the bitmap, 1 otherwise

Definition at line 539 of file rte_bitmap.h.