--- /dev/null
+/*
+ * rculfhash-mm-mmap.c
+ *
+ * mmap/reservation based memory management for Lock-Free RCU Hash Table
+ *
+ * Copyright 2011 - Lai Jiangshan <laijs@cn.fujitsu.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include "rculfhash-internal.h"
+
+#ifndef MAP_ANONYMOUS
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+
+/*
+ * The allocation scheme used by the mmap based RCU hash table is to make a
+ * large unaccessible mapping to reserve memory without allocating it.
+ * Then smaller chunks are allocated by overlapping read/write mappings which
+ * do allocate memory. Deallocation is done by an overlapping unaccessible
+ * mapping.
+ *
+ * This scheme was tested on Linux, macOS and Solaris. However, on Cygwin the
+ * mmap wrapper is based on the Windows NtMapViewOfSection API which doesn't
+ * support overlapping mappings.
+ *
+ * An alternative to the overlapping mappings is to use mprotect to change the
+ * protection on chunks of the large mapping, read/write to allocate and none
+ * to deallocate. This works perfecty on Cygwin and Solaris but on Linux a
+ * call to madvise is also required to deallocate and it just doesn't work on
+ * macOS.
+ *
+ * For this reason, we keep to original scheme on all platforms except Cygwin.
+ */
+
+
+/* Reserve inaccessible memory space without allocating it */
+static
+void *memory_map(size_t length)
+{
+ void *ret;
+
+ ret = mmap(NULL, length, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (ret == MAP_FAILED) {
+ perror("mmap");
+ abort();
+ }
+ return ret;
+}
+
+static
+void memory_unmap(void *ptr, size_t length)
+{
+ if (munmap(ptr, length)) {
+ perror("munmap");
+ abort();
+ }
+}
+
+#ifdef __CYGWIN__
+/* Set protection to read/write to allocate a memory chunk */
+static
+void memory_populate(void *ptr, size_t length)
+{
+ if (mprotect(ptr, length, PROT_READ | PROT_WRITE)) {
+ perror("mprotect");
+ abort();
+ }
+}
+
+/* Set protection to none to deallocate a memory chunk */
+static
+void memory_discard(void *ptr, size_t length)
+{
+ if (mprotect(ptr, length, PROT_NONE)) {
+ perror("mprotect");
+ abort();
+ }
+}
+
+#else /* __CYGWIN__ */
+
+static
+void memory_populate(void *ptr, size_t length)
+{
+ if (mmap(ptr, length, PROT_READ | PROT_WRITE,
+ MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
+ -1, 0) != ptr) {
+ perror("mmap");
+ abort();
+ }
+}
+
+/*
+ * Discard garbage memory and avoid system save it when try to swap it out.
+ * Make it still reserved, inaccessible.
+ */
+static
+void memory_discard(void *ptr, size_t length)
+{
+ if (mmap(ptr, length, PROT_NONE,
+ MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
+ -1, 0) != ptr) {
+ perror("mmap");
+ abort();
+ }
+}
+#endif /* __CYGWIN__ */
+
+static
+void lttng_ust_lfht_alloc_bucket_table(struct lttng_ust_lfht *ht, unsigned long order)
+{
+ if (order == 0) {
+ if (ht->min_nr_alloc_buckets == ht->max_nr_buckets) {
+ /* small table */
+ ht->tbl_mmap = calloc(ht->max_nr_buckets,
+ sizeof(*ht->tbl_mmap));
+ assert(ht->tbl_mmap);
+ return;
+ }
+ /* large table */
+ ht->tbl_mmap = memory_map(ht->max_nr_buckets
+ * sizeof(*ht->tbl_mmap));
+ memory_populate(ht->tbl_mmap,
+ ht->min_nr_alloc_buckets * sizeof(*ht->tbl_mmap));
+ } else if (order > ht->min_alloc_buckets_order) {
+ /* large table */
+ unsigned long len = 1UL << (order - 1);
+
+ assert(ht->min_nr_alloc_buckets < ht->max_nr_buckets);
+ memory_populate(ht->tbl_mmap + len,
+ len * sizeof(*ht->tbl_mmap));
+ }
+ /* Nothing to do for 0 < order && order <= ht->min_alloc_buckets_order */
+}
+
+/*
+ * lttng_ust_lfht_free_bucket_table() should be called with decreasing order.
+ * When lttng_ust_lfht_free_bucket_table(0) is called, it means the whole
+ * lfht is destroyed.
+ */
+static
+void lttng_ust_lfht_free_bucket_table(struct lttng_ust_lfht *ht, unsigned long order)
+{
+ if (order == 0) {
+ if (ht->min_nr_alloc_buckets == ht->max_nr_buckets) {
+ /* small table */
+ poison_free(ht->tbl_mmap);
+ return;
+ }
+ /* large table */
+ memory_unmap(ht->tbl_mmap,
+ ht->max_nr_buckets * sizeof(*ht->tbl_mmap));
+ } else if (order > ht->min_alloc_buckets_order) {
+ /* large table */
+ unsigned long len = 1UL << (order - 1);
+
+ assert(ht->min_nr_alloc_buckets < ht->max_nr_buckets);
+ memory_discard(ht->tbl_mmap + len, len * sizeof(*ht->tbl_mmap));
+ }
+ /* Nothing to do for 0 < order && order <= ht->min_alloc_buckets_order */
+}
+
+static
+struct lttng_ust_lfht_node *bucket_at(struct lttng_ust_lfht *ht, unsigned long index)
+{
+ return &ht->tbl_mmap[index];
+}
+
+static
+struct lttng_ust_lfht *alloc_lttng_ust_lfht(unsigned long min_nr_alloc_buckets,
+ unsigned long max_nr_buckets)
+{
+ unsigned long page_bucket_size;
+
+ page_bucket_size = getpagesize() / sizeof(struct lttng_ust_lfht_node);
+ if (max_nr_buckets <= page_bucket_size) {
+ /* small table */
+ min_nr_alloc_buckets = max_nr_buckets;
+ } else {
+ /* large table */
+ min_nr_alloc_buckets = max(min_nr_alloc_buckets,
+ page_bucket_size);
+ }
+
+ return __default_alloc_lttng_ust_lfht(
+ <tng_ust_lfht_mm_mmap, sizeof(struct lttng_ust_lfht),
+ min_nr_alloc_buckets, max_nr_buckets);
+}
+
+const struct lttng_ust_lfht_mm_type lttng_ust_lfht_mm_mmap = {
+ .alloc_lttng_ust_lfht = alloc_lttng_ust_lfht,
+ .alloc_bucket_table = lttng_ust_lfht_alloc_bucket_table,
+ .free_bucket_table = lttng_ust_lfht_free_bucket_table,
+ .bucket_at = bucket_at,
+};
projects / deliverable / lttng-ust.git / blobdiff