[lttng-dev] [PATCH 12/12] add rculfhash-mm-mmap.c memory management

[Mathieu Desnoyers]

Merged as:

commit b0b5525153fce8abae07b9573da1d5169e02eb2b
Author: Lai Jiangshan <laijs at cn.fujitsu.com>
Date:   Mon Nov 28 08:41:10 2011 -0500

    add rculfhash-mm-mmap.c memory management
    
    [ Edit by Mathieu Desnoyers:
      - change "buckets" for "mmap" to better show the mapping between the
        union member and the mm plugin.
      - 80 col coding style fixups. ]
    
    Signed-off-by: Lai Jiangshan <laijs at cn.fujitsu.com>
    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>

diff --git a/Makefile.am b/Makefile.am
index 853ecd5..91a9fd1 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -35,7 +35,8 @@ if COMPAT_FUTEX
 COMPAT+=compat_futex.c
 endif
 
-RCULFHASH=rculfhash.c rculfhash-mm-order.c rculfhash-mm-chunk.c
+RCULFHASH = rculfhash.c rculfhash-mm-order.c rculfhash-mm-chunk.c \
+		rculfhash-mm-mmap.c
 
 lib_LTLIBRARIES = liburcu-common.la \
 		liburcu.la liburcu-qsbr.la \
diff --git a/rculfhash-internal.h b/rculfhash-internal.h
index f7c6590..cc14664 100644
--- a/rculfhash-internal.h
+++ b/rculfhash-internal.h
@@ -108,6 +108,12 @@ struct cds_lfht {
 		 * memory addressing.
 		 */
 		struct cds_lfht_node *tbl_chunk[0];
+
+		/*
+		 * Memory mapping with room for all possible buckets.
+		 * Their memory is allocated when needed.
+		 */
+		struct cds_lfht_node *tbl_mmap;
 	};
 };
 
diff --git a/rculfhash-mm-mmap.c b/rculfhash-mm-mmap.c
new file mode 100644
index 0000000..542c884
--- /dev/null
+++ b/rculfhash-mm-mmap.c
@@ -0,0 +1,160 @@
+/*
+ * rculfhash-mm-mmap.c
+ *
+ * mmap/reservation based memory management for Lock-Free RCU Hash Table
+ *
+ * Copyright 2011 - Lai Jiangshan <laijs at 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 <sys/mman.h>
+#include "rculfhash-internal.h"
+
+/* reserve inaccessible memory space without allocation any memory */
+static void *memory_map(size_t length)
+{
+	void *ret = mmap(NULL, length, PROT_NONE,
+			MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+	assert(ret != MAP_FAILED);
+	return ret;
+}
+
+static void memory_unmap(void *ptr, size_t length)
+{
+	int ret = munmap(ptr, length);
+
+	assert(ret == 0);
+}
+
+static void memory_populate(void *ptr, size_t length)
+{
+	void *ret = mmap(ptr, length, PROT_READ | PROT_WRITE,
+			MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+	assert(ret == ptr);
+}
+
+/*
+ * 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)
+{
+	void *ret = mmap(ptr, length, PROT_NONE,
+			MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+	assert(ret == ptr);
+}
+
+static
+void cds_lfht_alloc_bucket_table(struct cds_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 */
+}
+
+/*
+ * cds_lfht_free_bucket_table() should be called with decreasing order.
+ * When cds_lfht_free_bucket_table(0) is called, it means the whole
+ * lfht is destroyed.
+ */
+static
+void cds_lfht_free_bucket_table(struct cds_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 cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
+{
+	return &ht->tbl_mmap[index];
+}
+
+static
+struct cds_lfht *alloc_cds_lfht(unsigned long min_nr_alloc_buckets,
+		unsigned long max_nr_buckets)
+{
+	struct cds_lfht *ht;
+	unsigned long page_bucket_size = getpagesize() / sizeof(*ht->tbl_mmap);
+
+	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);
+	}
+
+	ht = calloc(1, sizeof(struct cds_lfht));
+	assert(ht);
+
+	ht->mm = &cds_lfht_mm_mmap;
+
+	ht->min_nr_alloc_buckets = min_nr_alloc_buckets;
+	ht->min_alloc_buckets_order =
+			get_count_order_ulong(min_nr_alloc_buckets);
+	ht->max_nr_buckets = max_nr_buckets;
+
+	ht->bucket_at = bucket_at;
+
+	return ht;
+}
+
+const struct cds_lfht_mm_type cds_lfht_mm_mmap = {
+	.alloc_cds_lfht = alloc_cds_lfht,
+	.alloc_bucket_table = cds_lfht_alloc_bucket_table,
+	.free_bucket_table = cds_lfht_free_bucket_table,
+	.bucket_at = bucket_at,
+};
diff --git a/urcu/rculfhash.h b/urcu/rculfhash.h
index 1224ea8..6ed7c8c 100644
--- a/urcu/rculfhash.h
+++ b/urcu/rculfhash.h
@@ -106,6 +106,7 @@ struct cds_lfht_mm_type {
 
 extern const struct cds_lfht_mm_type cds_lfht_mm_order;
 extern const struct cds_lfht_mm_type cds_lfht_mm_chunk;
+extern const struct cds_lfht_mm_type cds_lfht_mm_mmap;
 
 /*
  * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com