* 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.
*/
-#include <sys/mman.h>
+#ifndef USE_SYSTEM_MALLOC
+#define _BSD_SOURCE // so we get MAP_ANON on linux
+#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
+#include <sys/mman.h>
#include "common.h"
+#include "rlocal.h"
#include "lwt.h"
-#include "tls.h"
-#define GET_SCALE(n) (sizeof(n)*8-__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
-#define REGION_SIZE (1 << REGION_SCALE)
-#define HEADER_REGION_SCALE 22 // 4MB is space enough for headers for over 2,000,000 regions
+#ifndef NBD32
+#define MAX_SCALE 36 // allocate blocks up to 64GB (arbitrary, could be bigger)
+#define MIN_SCALE 3 // smallest allocated block is 8 bytes
+#define MAX_POINTER_BITS 48
+#define PAGE_SCALE 21 // 2MB pages
+#else
+#define MAX_SCALE 31
+#define MIN_SCALE 2 // smallest allocated block is 4 bytes
+#define MAX_POINTER_BITS 32
+#define PAGE_SCALE 12 // 4KB pages
+#endif
+#define PAGE_SIZE (1ULL << PAGE_SCALE)
+#define HEADERS_SIZE (((size_t)1ULL << (MAX_POINTER_BITS - PAGE_SCALE)) * sizeof(header_t))
typedef struct block {
struct block *next;
} block_t;
-// region header
+// TODO: Break the page header into two parts. The first part is located in the header region. The
+// second part is located on the page and is only used when there are free items.
typedef struct header {
- char owner; // thread id of owner
- char scale; // log2 of the block size
+#ifdef RECYCLE_PAGES
+ struct header *next;
+ struct header *prev;
+ block_t *free_list; // list of free blocks
+ int num_in_use;
+#endif//RECYCLE_PAGES
+ uint8_t owner; // thread id of owner
+ uint8_t scale; // log2 of the block size
} header_t;
-static header_t *region_header_ = NULL;
+#ifdef RECYCLE_PAGES
+typedef struct size_class {
+ header_t *active_page;
+ header_t *oldest_partial;
+ header_t *newest_partial;
+} size_class_t;
+#endif//RECYCLE_PAGES
+
+typedef struct tl {
+#ifndef RECYCLE_PAGES
+ block_t *free_list[MAX_SCALE+1];
+#else
+ header_t *free_pages;
+ size_class_t size_class[MAX_SCALE+1];
+#endif//RECYCLE_PAGES
+ 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;
-// TODO: experiment with different memory layouts (i.e. separate private and public lists)
-static block_t free_list_[MAX_NUM_THREADS][MAX_SCALE+1][MAX_NUM_THREADS];
+static tl_t tl_[MAX_NUM_THREADS] = {};
-static void *get_new_region (int scale) {
- if (scale < REGION_SCALE) {
- scale = REGION_SCALE;
+static inline header_t *get_header (void *r) {
+ ASSERT(((size_t)r >> PAGE_SCALE) < HEADERS_SIZE);
+ return headers_ + ((size_t)r >> PAGE_SCALE);
+}
+
+static void *get_new_region (int block_scale) {
+ int thread_index = GET_THREAD_INDEX();
+#ifdef RECYCLE_PAGES
+ tl_t *tl = &tl_[thread_index]; // thread-local data
+ if (block_scale <= PAGE_SCALE && tl->free_pages != NULL) {
+ void *region = tl->free_pages;
+ tl->free_pages = tl->free_pages->next;
+ get_header(region)->scale = block_scale;
+ return region;
}
- TRACE("m0", "get_new_region(): mmap new region scale: %llu", scale, 0);
- void *region = mmap(NULL, (1 << scale), PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0);
+#endif//RECYCLE_PAGES
+ size_t region_size = (1ULL << block_scale);
+ if (region_size < PAGE_SIZE) {
+ region_size = PAGE_SIZE;
+ }
+ void *region = mmap(NULL, region_size, PROT_READ|PROT_WRITE, MAP_NORESERVE|MAP_ANON|MAP_PRIVATE, -1, 0);
+ TRACE("m1", "get_new_region: mmapped new region %p (size %p)", region, region_size);
if (region == (void *)-1) {
perror("get_new_region: mmap");
exit(-1);
}
+ if ((size_t)region & (region_size - 1)) {
+ TRACE("m0", "get_new_region: region not aligned", 0, 0);
+ munmap(region, region_size);
+ region = mmap(NULL, region_size * 2, PROT_READ|PROT_WRITE, MAP_NORESERVE|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, region_size * 2);
+ void *aligned = (void *)(((size_t)region + region_size) & ~(region_size - 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 + region_size) - (char *)aligned;
+ if (extra) {
+ munmap((char *)aligned + region_size, extra);
+ TRACE("m0", "get_new_region: unmapped extra memory %p (size %p)", (char *)aligned + region_size, extra);
+ }
+ region = aligned;
+ }
assert(region);
+
+ header_t *h = get_header(region);
+ TRACE("m1", "get_new_region: header %p (%p)", h, h - headers_);
+ assert(h->scale == 0);
+ h->scale = block_scale;
+ h->owner = thread_index;
+
return region;
}
void mem_init (void) {
- assert(region_header_ == NULL);
- region_header_ = (header_t *)get_new_region(HEADER_REGION_SCALE);
- memset(region_header_, 0, REGION_SIZE);
+ assert(headers_ == NULL);
+ // Allocate space for the page headers. This could be a big chunk of memory on 64 bit systems,
+ // but it just takes up virtual address space. Physical space used by the headers is still
+ // proportional to the amount of memory the user mallocs.
+ headers_ = mmap(NULL, HEADERS_SIZE, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0);
+ TRACE("m1", "mem_init: header page %p", headers_, 0);
+
+ // initialize spsc queues
+ for (int i = 0; i < MAX_NUM_THREADS; ++i) {
+ for (int j = 0; j < MAX_NUM_THREADS; ++j) {
+ if (i != j) {
+ tl_[i].blocks_to[j] = (block_t *)&(tl_[j].blocks_from[i]);
+ }
+ }
+ }
}
-// 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?
void nbd_free (void *x) {
- LOCALIZE_THREAD_LOCAL(tid_, int);
+ TRACE("m1", "nbd_free: block %p page %p", x, (size_t)x & ~MASK(PAGE_SCALE));
+ ASSERT(x);
block_t *b = (block_t *)x;
- assert(((size_t)b >> REGION_SCALE) < ((1 << HEADER_REGION_SCALE) / sizeof(header_t)));
- header_t *h = region_header_ + ((size_t)b >> REGION_SCALE);
- TRACE("m0", "nbd_free(): block %p scale %llu", x, h->scale);
- block_t *l = &free_list_[(int)h->owner][(int)h->scale][tid_];
- TRACE("m0", "nbd_free(): free list %p first block %p", l, l->next);
- b->next = l->next;
- l->next = b;
-}
-
-// Allocate a block of memory at least size <n>. Blocks are binned in powers-of-two. Round up
-// <n> to the nearest power-of-two.
-//
-// First check the current thread's private free list for an available block. If no blocks are on
-// the private free list, pull all the available blocks off of the current thread's public free
-// lists and put them on the private free list. If we didn't find any blocks on the public free
-// lists, open a new region, break it up into blocks and put them on the private free list.
-void *nbd_malloc (size_t n) {
- LOCALIZE_THREAD_LOCAL(tid_, int);
- if (n < sizeof(block_t)) {
- n = sizeof(block_t);
+ header_t *h = get_header(x);
+ int b_scale = h->scale;
+ TRACE("m1", "nbd_free: header %p scale %llu", h, b_scale);
+ ASSERT(b_scale && b_scale <= MAX_SCALE);
+#ifdef RECYCLE_PAGES
+ if (b_scale > PAGE_SCALE) {
+ int rc = munmap(x, 1ULL << b_scale);
+ ASSERT(rc == 0);
+ rc = rc;
}
- int b_scale = GET_SCALE(n);
- assert(b_scale <= MAX_SCALE);
- TRACE("m0", "nbd_malloc(): size %llu scale %llu", n, b_scale);
- block_t *fls = free_list_[tid_][b_scale]; // our free lists
- block_t *pri = fls + tid_; // our private free list
- TRACE("m0", "nbd_malloc(): private free list %p first block %p", pri, pri->next);
-
- // If our private free list is empty, fill it up with blocks from our public free lists
- if (EXPECT_FALSE(pri->next == NULL)) {
- int cnt = 0;
- block_t *last = pri;
- for (int i = 0; i < MAX_NUM_THREADS; ++i) {
- TRACE("m0", "nbd_malloc(): searching public free lists (%llu)", i, 0);
- block_t *pub = fls + i; // one of our public free lists
- TRACE("m0", "nbd_malloc(): public free list %p first block %p", pub, pub->next);
- if (EXPECT_FALSE(pub == pri))
- continue;
-
- if (pub->next != NULL) {
- block_t *stolen = SYNC_SWAP(&pub->next, NULL);
- TRACE("m0", "nbd_malloc(): stole list %p first block %p", pub, stolen);
- if (stolen) {
- last->next = stolen;
- TRACE("m0", "nbd_malloc(): append to last block %p of private free list", last, 0);
- while (last->next) {
- ++cnt;
- TRACE("m0", "nbd_malloc(): find last block in list: last %p last->next %p",
- last, last->next);
- last = last->next;
- }
+#endif
+#ifndef NDEBUG
+ memset(b, 0xcd, (1ULL << b_scale)); // bear trap
+#endif
+ int thread_index = GET_THREAD_INDEX();
+ tl_t *tl = &tl_[thread_index]; // thread-local data
+ if (h->owner == thread_index) {
+ TRACE("m1", "nbd_free: private block, old free list head %p", tl->free_list[b_scale], 0);
+
+#ifndef RECYCLE_PAGES
+ b->next = tl->free_list[b_scale];
+ tl->free_list[b_scale] = b;
+#else //RECYCLE_PAGES
+ b->next = h->free_list;
+ h->free_list = b;
+ h->num_in_use--;
+ size_class_t *sc = &tl->size_class[b_scale];
+ if (sc->active_page != h) {
+ if (h->num_in_use == 0) {
+ // remove <h> from the partial-page list
+ if (h->next != NULL) { h->next->prev = h->prev; }
+ if (h->prev != NULL) { h->prev->next = h->next; }
+ // put <h> on the free-page list
+ h->next = tl->free_pages;
+ tl->free_pages = h;
+ } else {
+ // move <h> to the top of the partial-page list
+ if (h->next != NULL) {
+ h->next->prev = h->prev;
+ if (h->prev != NULL) { h->prev->next = h->next; }
+ h->prev = sc->newest_partial;
+ h->next = NULL;
+ sc->newest_partial = h;
}
}
}
- TRACE("m0", "nbd_malloc(): moved %llu blocks from public to private free lists", cnt, 0);
+#endif//RECYCLE_PAGES
+ } else {
+ // push <b> onto it's owner's queue
+ int b_owner = h->owner;
+ TRACE("m1", "nbd_free: owner %llu", b_owner, 0);
+
+ // The assignment statements are volatile to prevent the compiler from reordering them.
+ VOLATILE_DEREF(b).next = NULL;
+ VOLATILE_DEREF(tl->blocks_to[b_owner]).next = b;
- if (b_scale >= REGION_SCALE) {
- if (cnt == 0) {
- assert(pri->next == NULL);
- pri->next = (block_t *)get_new_region(b_scale);
- assert(pri->next->next == NULL);
- }
- assert(pri->next);
-
- } else if (cnt < (1 << (REGION_SCALE - b_scale - 1))) {
-
- // Even if we took a few blocks from our public lists we still break open a new region.
- // This guarentees that we are amortizing the cost of accessing our public lists accross
- // many nbd_malloc() calls.
- char *region = get_new_region(b_scale);
- size_t b_size = 1 << b_scale;
- for (int i = REGION_SIZE; i != 0; i -= b_size) {
- block_t *b = (block_t *)(region + i - b_size);
- b->next = pri->next;
- //TRACE("m1", "nbd_malloc(): put new block %p ahead of %p on private list", b, b->next);
- pri->next = b;
- *b = *b;
- }
+ tl->blocks_to[b_owner] = b;
+ }
+}
+
+static inline void process_incoming_blocks (tl_t *tl) {
+ for (int p = 0; p < MAX_NUM_THREADS; ++p) {
+ block_t *b = tl->blocks_from[p];
+ if (EXPECT_FALSE(b == NULL)) continue; // the queue is completely empty
+
+ // Leave the last block on the queue. Removing the last block on the queue would create a
+ // race with the producer thread putting a new block on the queue.
+ for (block_t *next = b->next; next != NULL; b = next, next = b->next) {
+ // push <b> onto the appropriate free list
+#ifndef RECYCLE_PAGES
+ int b_scale = get_header(b)->scale;
+ b->next = tl->free_list[b_scale];
+ tl->free_list[b_scale] = b;
+#else //RECYCLE_PAGES
+ header_t *h = get_header(b);
+ b->next = h->free_list;
+ h->free_list = b;
+#endif//RECYCLE_PAGES
}
+ tl->blocks_from[p] = b;
+ }
+}
- assert(pri->next);
+static inline block_t *pop_free_list (tl_t *tl, int scale) {
+#ifndef RECYCLE_PAGES
+ block_t **free_list = &tl->free_list[scale];
+#else //RECYCLE_PAGES
+ size_class_t *sc = &tl->size_class[scale];
+ if (EXPECT_FALSE(sc->active_page == NULL))
+ return NULL;
+ block_t **free_list = &sc->active_page->free_list;
+#endif//RECYCLE_PAGES
+ block_t *b = *free_list;
+ if (EXPECT_FALSE(b == NULL))
+ return NULL;
+ ASSERT(get_header(b)->scale == scale);
+ *free_list = b->next;
+ return b;
+}
+
+// Allocate a block of memory at least size <n>. Blocks are binned in powers-of-two. Round up <n> to
+// the nearest power of two.
+//
+// First check the current thread's free list for an available block. If there are no blocks on the
+// free list, pull items off of the current thread's incoming block queues and push them onto the
+// free list. If we didn't get an appropriate size block off of the block queues then allocate a new
+// page, break it up into blocks and push them onto the free list.
+void *nbd_malloc (size_t n) {
+ // the scale is the log base 2 of <n>, rounded up
+ int b_scale = (sizeof(void *) * __CHAR_BIT__) - __builtin_clzl((n) - 1);
+ TRACE("m1", "nbd_malloc: size %llu (scale %llu)", n, b_scale);
+
+ if (EXPECT_FALSE(b_scale < MIN_SCALE)) { b_scale = MIN_SCALE; }
+ if (EXPECT_FALSE(b_scale > MAX_SCALE)) { return NULL; }
+
+ tl_t *tl = &tl_[GET_THREAD_INDEX()]; // thread-local data
+
+ block_t *b = pop_free_list(tl, b_scale);
+ if (b != NULL) {
+ TRACE("m1", "nbd_malloc: returning block %p", b, 0);
+ return b;
+ assert(b);
+ }
+
+ // The free list is empty so process blocks freed from other threads and then check again.
+ process_incoming_blocks(tl);
+ b = pop_free_list(tl, b_scale);
+ if (b != NULL) {
+ TRACE("m1", "nbd_malloc: returning block %p", b, 0);
+ return b;
+ assert(b);
+ }
+
+#ifdef RECYCLE_PAGES
+ // The current active page is completely allocated. Make the oldest partially allocated page
+ // the new active page.
+ size_class_t *sc = &tl->size_class[b_scale];
+ if (sc->oldest_partial != NULL) {
+ sc->active_page = sc->oldest_partial;
+ sc->oldest_partial = sc->oldest_partial->next;
+ sc->oldest_partial->prev = NULL;
+ b = pop_free_list(tl, b_scale);
+ ASSERT(b != NULL);
+ TRACE("m1", "nbd_malloc: returning block %p", b, 0);
+ return b;
+ assert(b);
}
+ // There are no partially allocated pages so get a new page.
- // Pull a block off of our private free list.
- block_t *b = pri->next;
- TRACE("m0", "nbd_malloc(): take block %p off of of private list (new head is %p)", b, pri->next);
- pri->next = b->next;
+#endif//RECYCLE_PAGES
+ // Get a new page.
+ char *page = get_new_region(b_scale);
+ b = (block_t *)page; // grab the first block on the page
+
+ // Break up the remainder of the page into blocks and put them on the free list. Start at the
+ // end of the page so that the free list ends up in increasing order, for ease of debugging.
+ if (b_scale < PAGE_SCALE) {
+ size_t block_size = (1ULL << b_scale);
+ block_t *head = NULL;
+ for (int offset = PAGE_SIZE - block_size; offset > 0; offset -= block_size) {
+ block_t *x = (block_t *)(page + offset);
+ x->next = head; head = x;
+ }
+#ifndef RECYCLE_PAGES
+ tl->free_list[b_scale] = head;
+#else //RECYCLE_PAGES
+ sc->active_page = get_header(page);
+ sc->active_page->free_list = head;
+#endif//RECYCLE_PAGES
+ }
+
+ TRACE("m1", "nbd_malloc: returning block %p from new region %p", b, (size_t)b & ~MASK(PAGE_SCALE));
assert(b);
return b;
}
+#else//USE_SYSTEM_MALLOC
+#include <stdlib.h>
+#include "common.h"
+#include "rlocal.h"
+#include "lwt.h"
+
+void mem_init (void) {
+ return;
+}
+
+void nbd_free (void *x) {
+ TRACE("m1", "nbd_free: %p", x, 0);
+#ifndef NDEBUG
+ memset(x, 0xcd, sizeof(void *)); // bear trap
+#endif//NDEBUG
+ free(x);
+ return;
+}
+
+void *nbd_malloc (size_t n) {
+ TRACE("m1", "nbd_malloc: request size %llu", n, 0);
+ void *x = malloc(n);
+ TRACE("m1", "nbd_malloc: returning %p", x, 0);
+ return x;
+}
+#endif//USE_SYSTEM_MALLOC
projects / nbds / blobdiff