[ltt-dev] [PATCH 07/10 round10] add LFHT_MEMORY_RESERVED low level memory management

[Lai Jiangshan]

Signed-off-by: Lai Jiangshan <laijs at cn.fujitsu.com>
---
 rculfhash.c |  119 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 118 insertions(+), 1 deletions(-)

diff --git a/rculfhash.c b/rculfhash.c
index ae1177f..b764dc1 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -155,6 +155,7 @@
 #include <stdio.h>
 #include <stdint.h>
 #include <string.h>
+#include <sys/mman.h>
 
 #include "config.h"
 #include <urcu.h>
@@ -172,7 +173,7 @@
 #define dbg_printf(fmt, args...)
 #endif
 
-#if !defined(LFHT_MEMORY_ORDER) && !defined(LFHT_MEMORY_CHUNK)
+#if !defined(LFHT_MEMORY_ORDER) && !defined(LFHT_MEMORY_CHUNK) && !defined(LFHT_MEMORY_RESERVED)
 #define LFHT_MEMORY_ORDER
 #endif
 
@@ -262,6 +263,13 @@ struct rcu_table {
 	 * levels to improve cache locality for small index orders.
 	 */
 	struct cds_lfht_node *tbl[MAX_TABLE_ORDER];
+#elif defined(LFHT_MEMORY_RESERVED)
+	/*
+	 * Contains all the room of buckets without memory allocated.
+	 * All the per order-index-level bucket node tables will be allocated
+	 * inside it when used. It achieves extreme simple bucket indexing.
+	 */
+	struct cds_lfht_node *tbl;
 #endif
 };
 
@@ -840,6 +848,115 @@ struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
 	offset = index & (ht->min_alloc_size - 1);
 	return &ht->tbl[chunk][offset];
 }
+#elif defined(LFHT_MEMORY_RESERVED)
+static
+struct cds_lfht *_cds_lfht_alloc(unsigned long min_alloc_size,
+		unsigned long max_size)
+{
+	struct cds_lfht *ht;
+	unsigned long page_bucket_size = getpagesize() / sizeof(*ht->t.tbl);
+
+	if (max_size <= page_bucket_size) /* small table */
+		min_alloc_size = max_size;
+	else /* large table */
+		min_alloc_size = max(min_alloc_size, page_bucket_size);
+
+	ht = calloc(1, sizeof(struct cds_lfht));
+	assert(ht);
+
+	ht->min_alloc_size = min_alloc_size;
+	ht->min_alloc_order = get_count_order_ulong(min_alloc_size);
+	ht->max_size = max_size;
+
+	return ht;
+}
+
+/* reserve inaccessible memory space without allocation any memory */
+static void *memory_reserve(size_t length)
+{
+	void *ret = mmap(NULL, length, PROT_NONE, MAP_ANONYMOUS, -1, 0);
+
+	assert(ret != MAP_FAILED);
+	return ret;
+}
+
+static void memory_dereserve(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_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_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_alloc_size == ht->max_size) { /* small table */
+			ht->t.tbl = calloc(ht->max_size, sizeof(*ht->t.tbl));
+			assert(ht->t.tbl);
+			return;
+		}
+		/* large table */
+		ht->t.tbl = memory_reserve(ht->max_size * sizeof(*ht->t.tbl));
+		memory_populate(ht->t.tbl, ht->min_alloc_size * sizeof(*ht->t.tbl));
+	} else if (order > ht->min_alloc_order) { /* large table */
+		unsigned long len = 1UL << (order - 1);
+
+		assert(ht->min_alloc_size < ht->max_size);
+		memory_populate(ht->t.tbl + len, len * sizeof(*ht->t.tbl));
+	}
+	/* Nothing to do for 0 < order && order <= ht->min_alloc_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_alloc_size == ht->max_size) { /* small table */
+			poison_free(ht->t.tbl);
+			return;
+		}
+		/* large table */
+		memory_dereserve(ht->t.tbl, ht->max_size * sizeof(*ht->t.tbl));
+	} else if (order > ht->min_alloc_order) { /* large table */
+		unsigned long len = 1UL << (order - 1);
+
+		assert(ht->min_alloc_size < ht->max_size);
+		memory_discard(ht->t.tbl + len, len * sizeof(*ht->t.tbl));
+	}
+	/* Nothing to do for 0 < order && order <= ht->min_alloc_order */
+}
+
+static inline
+struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
+{
+	return &ht->t.tbl[index];
+}
 #else
 /* LFHT_MEMORY_ORDER */
 static
-- 
1.7.4.4