* Written by Josh Dybnis and released to the public domain, as explained at
* http://creativecommons.org/licenses/publicdomain
*
- * Extreamly fast multi-threaded malloc. 64 bit platforms only!
+ * Extreamly fast multi-threaded malloc.
*/
#define _BSD_SOURCE // so we get MAP_ANON on linux
#include <sys/mman.h>
#include "lwt.h"
#define GET_SCALE(n) (sizeof(void *)*__CHAR_BIT__ - __builtin_clzl((n) - 1)) // log2 of <n>, rounded up
-#define MAX_SCALE 31 // allocate blocks up to 4GB in size (arbitrary, could be bigger)
-#define REGION_SCALE 22 // 4MB regions
+#ifndef NBD32
+#define MAX_POINTER_BITS 48
+#define REGION_SCALE 21 // 2mb regions
+#else
+#define MAX_POINTER_BITS 32
+#define REGION_SCALE 12 // 4kb regions
+#endif
#define REGION_SIZE (1 << REGION_SCALE)
-#define HEADER_REGION_SCALE 22 // 4MB is space enough for headers for over 2,000,000 regions
-#define HEADER_REGION_SIZE (1 << HEADER_REGION_SCALE)
-#define HEADER_COUNT (HEADER_REGION_SIZE / sizeof(header_t))
+#define HEADER_REGION_SCALE ((MAX_POINTER_BITS - REGION_SCALE) + GET_SCALE(sizeof(header_t)))
+#define MAX_SCALE 31 // allocate blocks up to 4GB in size (arbitrary, could be bigger)
typedef struct block {
struct block *next;
uint8_t scale; // log2 of the block size
} header_t;
-typedef struct private_list {
- block_t *head;
- uint32_t next_pub;
- uint32_t count;
-} private_list_t;
+typedef struct tl {
+ block_t *free_blocks[MAX_SCALE+1];
+ block_t *blocks_from[MAX_NUM_THREADS];
+ block_t *blocks_to[MAX_NUM_THREADS];
+} __attribute__((aligned(CACHE_LINE_SIZE))) tl_t ;
static header_t *headers_ = NULL;
-static block_t *pub_free_list_[MAX_NUM_THREADS][MAX_SCALE+1][MAX_NUM_THREADS] = {};
-static private_list_t pri_free_list_[MAX_NUM_THREADS][MAX_SCALE+1] = {};
+static tl_t tl_[MAX_NUM_THREADS] = {};
static inline header_t *get_header (void *r) {
- return headers_ + (((size_t)r >> REGION_SCALE) & (HEADER_COUNT - 1));
+ return headers_ + ((size_t)r >> REGION_SCALE);
}
static void *get_new_region (int block_scale) {
sz = REGION_SIZE;
}
void *region = mmap(NULL, sz, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0);
- TRACE("m1", "get_new_region: mmap new region %p (size %p)", region, sz);
+ TRACE("m1", "get_new_region: mmapped new region %p (size %p)", region, sz);
if (region == (void *)-1) {
perror("get_new_region: mmap");
exit(-1);
}
+ if ((size_t)region & (sz - 1)) {
+ TRACE("m0", "get_new_region: region not aligned", 0, 0);
+ munmap(region, sz);
+ region = mmap(NULL, sz * 2, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0);
+ if (region == (void *)-1) {
+ perror("get_new_region: mmap");
+ exit(-1);
+ }
+ TRACE("m0", "get_new_region: mmapped new region %p (size %p)", region, sz * 2);
+ void *aligned = (void *)(((size_t)region + sz) & ~(sz - 1));
+ size_t extra = (char *)aligned - (char *)region;
+ if (extra) {
+ munmap(region, extra);
+ TRACE("m0", "get_new_region: unmapped extra memory %p (size %p)", region, extra);
+ }
+ extra = ((char *)region + sz) - (char *)aligned;
+ if (extra) {
+ munmap((char *)aligned + sz, extra);
+ TRACE("m0", "get_new_region: unmapped extra memory %p (size %p)", (char *)aligned + sz, extra);
+ }
+ region = aligned;
+ }
assert(region);
if (headers_ != NULL) {
LOCALIZE_THREAD_LOCAL(tid_, int);
return region;
}
-void mem_init (void) {
+__attribute__ ((constructor(101))) void mem_init (void) {
#ifdef USE_SYSTEM_MALLOC
return;
#endif
assert(headers_ == NULL);
- headers_ = (header_t *)get_new_region(HEADER_REGION_SCALE);
+ // Allocate a region for the region headers. This could be a big chunk of memory (256MB) on 64 bit systems,
+ // but it just takes up virtual address space. Physical address space used by the headers is still proportional
+ // to the amount of memory we alloc.
+ headers_ = (header_t *)get_new_region(HEADER_REGION_SCALE);
TRACE("m1", "mem_init: header region %p", headers_, 0);
- memset(headers_, 0, HEADER_REGION_SIZE);
+ memset(headers_, 0, (1 << HEADER_REGION_SCALE));
}
// Put <x> onto its owner's public free list (in the appropriate size bin).
//
-// TODO: maybe we want to munmap() larger size blocks to reclaim virtual address space?
+// TODO: maybe we want to munmap() larger size blocks?
void nbd_free (void *x) {
#ifdef USE_SYSTEM_MALLOC
TRACE("m1", "nbd_free: %p", x, 0);
#ifndef NDEBUG
- memset(x, 0xcd, sizeof(void *)); // bear trap
+ //memset(x, 0xcd, sizeof(void *)); // bear trap
#endif//NDEBUG
free(x);
return;
#ifndef NDEBUG
memset(b, 0xcd, (1 << h->scale)); // bear trap
#endif
+ tl_t *tl = &tl_[tid_]; // thread-local data
if (h->owner == tid_) {
- TRACE("m1", "nbd_free: private block, old free list head %p", pri_free_list_[tid_][h->scale].head, 0);
- b->next = pri_free_list_[tid_][h->scale].head;
- pri_free_list_[tid_][h->scale].head = b;
+ TRACE("m1", "nbd_free: private block, old free list head %p", tl->free_blocks[h->scale], 0);
+ b->next = tl->free_blocks[h->scale];
+ tl->free_blocks[h->scale] = b;
} else {
- TRACE("m1", "nbd_free: owner %llu free list head %p", h->owner, pub_free_list_[h->owner][h->scale][tid_]);
- do {
- b->next = pub_free_list_[h->owner][h->scale][tid_];
- } while (SYNC_CAS(&pub_free_list_[h->owner][h->scale][tid_], b->next, b) != b->next);
+ TRACE("m1", "nbd_free: owner %llu", h->owner, 0);
+ // push <b> onto it's owner's queue
+ VOLATILE(b->next) = NULL;
+ if (EXPECT_FALSE(tl->blocks_to[h->owner] == NULL)) {
+ VOLATILE(tl_[h->owner].blocks_from[tid_]) = b;
+ } else {
+ VOLATILE(tl->blocks_to[h->owner]->next) = b;
+ }
+ tl->blocks_to[h->owner] = b;
}
}
assert(b_scale <= MAX_SCALE);
TRACE("m1", "nbd_malloc: request size %llu (scale %llu)", n, b_scale);
LOCALIZE_THREAD_LOCAL(tid_, int);
- private_list_t *pri = &pri_free_list_[tid_][b_scale]; // our private free list
+ tl_t *tl = &tl_[tid_]; // thread-local data
// If our private free list is empty, try to find blocks on our public free list. If that fails,
// allocate a new region.
- if (EXPECT_FALSE(pri->head == NULL)) {
- block_t **pubs = pub_free_list_[tid_][b_scale]; // our public free lists
- while (1) {
- // look for blocks on our public free lists round robin
- pri->next_pub = (pri->next_pub+1) & (MAX_NUM_THREADS-1);
-
- TRACE("m1", "nbd_malloc: searching public free list %llu", pri->next_pub, 0);
- if (pri->next_pub == tid_) {
- uint32_t count = pri->count;
- pri->count = 0;
- // If we haven't gotten at least half a region's worth of block's from our public lists
- // we allocate a new region. This guarentees that we amortize the cost of accessing our
- // public lists accross enough nbd_malloc() calls.
- uint32_t min_count = b_scale > REGION_SCALE ? 1 << (b_scale-REGION_SCALE-1) : 1;
- if (count < min_count) {
- char *region = get_new_region(b_scale);
- size_t b_size = 1 << b_scale;
- size_t region_size = (b_size < REGION_SIZE) ? REGION_SIZE : b_size;
- for (int i = region_size; i != 0; i -= b_size) {
- block_t *b = (block_t *)(region + i - b_size);
- b->next = pri->head;
- pri->head = b;
- }
- pri->count = 0;
- break;
+ if (EXPECT_FALSE(tl->free_blocks[b_scale] == NULL)) {
+ for (int i = 0; i < MAX_NUM_THREADS; ++ i) {
+ block_t *x = tl->blocks_from[i];
+ if (x != NULL) {
+ block_t *next = x->next;
+ if (next != NULL) {
+ do {
+ header_t *h = get_header(x);
+ x->next = tl->free_blocks[h->scale];
+ tl->free_blocks[h->scale] = x;
+ x = next;
+ next = x->next;
+ } while (next != NULL);
+ tl->blocks_from[i] = x;
}
- } else if (pubs[pri->next_pub] != NULL) {
- block_t *stolen = SYNC_SWAP(&pubs[pri->next_pub], NULL);
- TRACE("m1", "nbd_malloc: stole list %p", stolen, 0);
- if (stolen == NULL)
- continue;
- pri->head = stolen;
- break;
}
}
- assert(pri->head);
+ // allocate a new region
+ if (tl->free_blocks[b_scale] == NULL) {
+ char *region = get_new_region(b_scale);
+ size_t b_size = 1 << b_scale;
+ size_t region_size = (b_size < REGION_SIZE) ? REGION_SIZE : b_size;
+ for (int i = region_size; i != 0; i -= b_size) {
+ block_t *b = (block_t *)(region + i - b_size);
+ b->next = tl->free_blocks[b_scale];
+ tl->free_blocks[b_scale] = b;
+ }
+ }
+ assert(tl->free_blocks[b_scale] != NULL);
}
// Pull a block off of our private free list.
- block_t *b = pri->head;
+ block_t *b = tl->free_blocks[b_scale];
TRACE("m1", "nbd_malloc: returning block %p (region %p) from private list", b, (size_t)b & ~MASK(REGION_SCALE));
- assert(b);
+ ASSERT(b);
ASSERT(get_header(b)->scale == b_scale);
- pri->head = b->next;
- pri->count++;
+ tl->free_blocks[b_scale] = b->next;
return b;
}
projects / nbds / blobdiff