+++ /dev/null
-/*
- * 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!
- */
-#include <sys/mman.h>
-#include <stdio.h>
-#include <errno.h>
-#include "common.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
-
-typedef struct block {
- struct block *next;
-} block_t;
-
-// region header
-typedef struct header {
- char owner; // thread id of owner
- char scale; // log2 of the block size
-} header_t;
-
-static header_t *region_header_ = 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 void *get_new_region (int scale) {
- if (scale < REGION_SCALE) {
- scale = REGION_SCALE;
- }
- 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);
- if (region == (void *)-1) {
- perror("get_new_region: mmap");
- exit(-1);
- }
- assert(region);
- 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);
-}
-
-// 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);
- 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);
- }
- 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;
- }
- }
- }
- }
- TRACE("m0", "nbd_malloc(): moved %llu blocks from public to private free lists", cnt, 0);
-
- 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;
- }
- }
-
- assert(pri->next);
- }
-
- // 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;
-
- assert(b);
- return b;
-}
projects / nbds / blobdiff