--- /dev/null
+/*
+ * Example memory allocator with pool allocation for small sizes and
+ * fallback into malloc/realloc/free for larger sizes or when the pools
+ * are exhausted.
+ *
+ * Useful to reduce memory churn or work around a platform allocator
+ * that doesn't handle a lot of small allocations efficiently.
+ */
+
+#include "duktape.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+
+/* Define to enable some debug printfs. */
+/* #define DUK_ALLOC_HYBRID_DEBUG */
+
+typedef struct {
+ size_t size;
+ int count;
+} pool_size_spec;
+
+static pool_size_spec pool_sizes[] = {
+ { 32, 1024 },
+ { 48, 2048 },
+ { 64, 2048 },
+ { 128, 2048 },
+ { 256, 512 },
+ { 1024, 64 },
+ { 2048, 32 }
+};
+
+#define NUM_POOLS (sizeof(pool_sizes) / sizeof(pool_size_spec))
+
+/* This must fit into the smallest pool entry. */
+struct pool_free_entry;
+typedef struct pool_free_entry pool_free_entry;
+struct pool_free_entry {
+ pool_free_entry *next;
+};
+
+typedef struct {
+ pool_free_entry *free;
+ char *alloc_start;
+ char *alloc_end;
+ size_t size;
+ int count;
+} pool_header;
+
+typedef struct {
+ pool_header headers[NUM_POOLS];
+ size_t pool_max_size;
+ char *alloc_start;
+ char *alloc_end;
+} pool_state;
+
+#define ADDR_IN_STATE_ALLOC(st,p) \
+ ((char *) (p) >= (st)->alloc_start && (char *) (p) < (st)->alloc_end)
+#define ADDR_IN_HEADER_ALLOC(hdr,p) \
+ ((char *) (p) >= (hdr)->alloc_start && (char *) (p) < (hdr)->alloc_end)
+
+#ifdef DUK_ALLOC_HYBRID_DEBUG
+static void dump_pool_state(pool_state *st) {
+ pool_free_entry *free;
+ int free_len;
+ int i;
+
+ printf("=== Pool state: st=%p\n", (void *) st);
+ for (i = 0; i < (int) NUM_POOLS; i++) {
+ pool_header *hdr = st->headers + i;
+
+ for (free = hdr->free, free_len = 0; free != NULL; free = free->next) {
+ free_len++;
+ }
+
+ printf("[%d]: size %ld, count %ld, used %ld, free list len %ld\n",
+ i, (long) hdr->size, (long) hdr->count,
+ (long) (hdr->count - free_len),
+ (long) free_len);
+ }
+}
+#else
+static void dump_pool_state(pool_state *st) {
+ (void) st;
+}
+#endif
+
+void *duk_alloc_hybrid_init(void) {
+ pool_state *st;
+ size_t total_size, max_size;
+ int i, j;
+ char *p;
+
+ st = (pool_state *) malloc(sizeof(pool_state));
+ if (!st) {
+ return NULL;
+ }
+ memset((void *) st, 0, sizeof(pool_state));
+ st->alloc_start = NULL;
+ st->alloc_end = NULL;
+
+ for (i = 0, total_size = 0, max_size = 0; i < (int) NUM_POOLS; i++) {
+#ifdef DUK_ALLOC_HYBRID_DEBUG
+ printf("Pool %d: size %ld, count %ld\n", i, (long) pool_sizes[i].size, (long) pool_sizes[i].count);
+#endif
+ total_size += pool_sizes[i].size * pool_sizes[i].count;
+ if (pool_sizes[i].size > max_size) {
+ max_size = pool_sizes[i].size;
+ }
+ }
+#ifdef DUK_ALLOC_HYBRID_DEBUG
+ printf("Total size %ld, max pool size %ld\n", (long) total_size, (long) max_size);
+#endif
+
+ st->alloc_start = (char *) malloc(total_size);
+ if (!st->alloc_start) {
+ free(st);
+ return NULL;
+ }
+ st->alloc_end = st->alloc_start + total_size;
+ st->pool_max_size = max_size;
+ memset((void *) st->alloc_start, 0, total_size);
+
+ for (i = 0, p = st->alloc_start; i < (int) NUM_POOLS; i++) {
+ pool_header *hdr = st->headers + i;
+
+ hdr->alloc_start = p;
+ hdr->alloc_end = p + pool_sizes[i].size * pool_sizes[i].count;
+ hdr->free = (pool_free_entry *) (void *) p;
+ hdr->size = pool_sizes[i].size;
+ hdr->count = pool_sizes[i].count;
+
+ for (j = 0; j < pool_sizes[i].count; j++) {
+ pool_free_entry *ent = (pool_free_entry *) (void *) p;
+ if (j == pool_sizes[i].count - 1) {
+ ent->next = (pool_free_entry *) NULL;
+ } else {
+ ent->next = (pool_free_entry *) (void *) (p + pool_sizes[i].size);
+ }
+ p += pool_sizes[i].size;
+ }
+ }
+
+ dump_pool_state(st);
+
+ /* Use 'st' as udata. */
+ return (void *) st;
+}
+
+void *duk_alloc_hybrid(void *udata, duk_size_t size) {
+ pool_state *st = (pool_state *) udata;
+ int i;
+ void *new_ptr;
+
+#if 0
+ dump_pool_state(st);
+#endif
+
+ if (size == 0) {
+ return NULL;
+ }
+ if (size > st->pool_max_size) {
+#ifdef DUK_ALLOC_HYBRID_DEBUG
+ printf("alloc fallback: %ld\n", (long) size);
+#endif
+ return malloc(size);
+ }
+
+ for (i = 0; i < (int) NUM_POOLS; i++) {
+ pool_header *hdr = st->headers + i;
+ if (hdr->size < size) {
+ continue;
+ }
+
+ if (hdr->free) {
+#if 0
+ printf("alloc from pool: %ld -> pool size %ld\n", (long) size, (long) hdr->size);
+#endif
+ new_ptr = (void *) hdr->free;
+ hdr->free = hdr->free->next;
+ return new_ptr;
+ } else {
+#ifdef DUK_ALLOC_HYBRID_DEBUG
+ printf("alloc out of pool entries: %ld -> pool size %ld\n", (long) size, (long) hdr->size);
+#endif
+ break;
+ }
+ }
+
+#ifdef DUK_ALLOC_HYBRID_DEBUG
+ printf("alloc fallback (out of pool): %ld\n", (long) size);
+#endif
+ return malloc(size);
+}
+
+void *duk_realloc_hybrid(void *udata, void *ptr, duk_size_t size) {
+ pool_state *st = (pool_state *) udata;
+ void *new_ptr;
+ int i;
+
+#if 0
+ dump_pool_state(st);
+#endif
+
+ if (ADDR_IN_STATE_ALLOC(st, ptr)) {
+ /* 'ptr' cannot be NULL. */
+ for (i = 0; i < (int) NUM_POOLS; i++) {
+ pool_header *hdr = st->headers + i;
+ if (ADDR_IN_HEADER_ALLOC(hdr, ptr)) {
+ if (size <= hdr->size) {
+ /* Still fits, no shrink support. */
+#if 0
+ printf("realloc original from pool: still fits, size %ld, pool size %ld\n",
+ (long) size, (long) hdr->size);
+#endif
+ return ptr;
+ }
+
+ new_ptr = duk_alloc_hybrid(udata, size);
+ if (!new_ptr) {
+#ifdef DUK_ALLOC_HYBRID_DEBUG
+ printf("realloc original from pool: needed larger size, failed to alloc\n");
+#endif
+ return NULL;
+ }
+ memcpy(new_ptr, ptr, hdr->size);
+
+ ((pool_free_entry *) ptr)->next = hdr->free;
+ hdr->free = (pool_free_entry *) ptr;
+#if 0
+ printf("realloc original from pool: size %ld, pool size %ld\n", (long) size, (long) hdr->size);
+#endif
+ return new_ptr;
+ }
+ }
+#ifdef DUK_ALLOC_HYBRID_DEBUG
+ printf("NEVER HERE\n");
+#endif
+ return NULL;
+ } else if (ptr != NULL) {
+ if (size == 0) {
+ free(ptr);
+ return NULL;
+ } else {
+#ifdef DUK_ALLOC_HYBRID_DEBUG
+ printf("realloc fallback: size %ld\n", (long) size);
+#endif
+ return realloc(ptr, size);
+ }
+ } else {
+#if 0
+ printf("realloc NULL ptr, call alloc: %ld\n", (long) size);
+#endif
+ return duk_alloc_hybrid(udata, size);
+ }
+}
+
+void duk_free_hybrid(void *udata, void *ptr) {
+ pool_state *st = (pool_state *) udata;
+ int i;
+
+#if 0
+ dump_pool_state(st);
+#endif
+
+ if (!ADDR_IN_STATE_ALLOC(st, ptr)) {
+ if (ptr == NULL) {
+ return;
+ }
+#if 0
+ printf("free out of pool: %p\n", (void *) ptr);
+#endif
+ free(ptr);
+ return;
+ }
+
+ for (i = 0; i < (int) NUM_POOLS; i++) {
+ pool_header *hdr = st->headers + i;
+ if (ADDR_IN_HEADER_ALLOC(hdr, ptr)) {
+ ((pool_free_entry *) ptr)->next = hdr->free;
+ hdr->free = (pool_free_entry *) ptr;
+#if 0
+ printf("free from pool: %p\n", ptr);
+#endif
+ return;
+ }
+ }
+
+#ifdef DUK_ALLOC_HYBRID_DEBUG
+ printf("NEVER HERE\n");
+#endif
+}
projects / ceph.git / blobdiff