[PATCH v4 2/3] fast-import: introduce mem_pool type

[Jameson Miller <jamill@microsoft.com>]

Introduce the mem_pool type which encapsulates all the information necessary to
manage a pool of memory. This change moves the existing variables in
fast-import used to support the global memory pool to use this structure. It
also renames variables that are no longer used by memory pools to reflect their
more scoped usage.

These changes allow for the multiple instances of a memory pool to
exist and be reused outside of fast-import. In a future commit the
mem_pool type will be moved to its own file.

Signed-off-by: Jameson Miller <jamill@microsoft.com>
---
 fast-import.c | 81 ++++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 52 insertions(+), 29 deletions(-)

diff --git a/fast-import.c b/fast-import.c
index 38af0a294b..48d4797ab5 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -218,6 +218,19 @@ struct mp_block {
 	uintmax_t space[FLEX_ARRAY]; /* more */
 };
 
+struct mem_pool {
+	struct mp_block *mp_block;
+
+	/*
+	 * The amount of available memory to grow the pool by.
+	 * This size does not include the overhead for the mp_block.
+	 */
+	size_t block_alloc;
+
+	/* The total amount of memory allocated by the pool. */
+	size_t pool_alloc;
+};
+
 struct atom_str {
 	struct atom_str *next_atom;
 	unsigned short str_len;
@@ -306,9 +319,8 @@ static int global_argc;
 static const char **global_argv;
 
 /* Memory pools */
-static size_t mem_pool_alloc = 2*1024*1024 - sizeof(struct mp_block);
-static size_t total_allocd;
-static struct mp_block *mp_block_head;
+static struct mem_pool fi_mem_pool =  {NULL, 2*1024*1024 -
+				       sizeof(struct mp_block), 0 };
 
 /* Atom management */
 static unsigned int atom_table_sz = 4451;
@@ -343,6 +355,7 @@ static unsigned int tree_entry_alloc = 1000;
 static void *avail_tree_entry;
 static unsigned int avail_tree_table_sz = 100;
 static struct avail_tree_content **avail_tree_table;
+static size_t tree_entry_allocd;
 static struct strbuf old_tree = STRBUF_INIT;
 static struct strbuf new_tree = STRBUF_INIT;
 
@@ -636,7 +649,21 @@ static unsigned int hc_str(const char *s, size_t len)
 	return r;
 }
 
-static void *pool_alloc(size_t len)
+static struct mp_block *mem_pool_alloc_block(struct mem_pool *mem_pool, size_t block_alloc)
+{
+	struct mp_block *p;
+
+	mem_pool->pool_alloc += sizeof(struct mp_block) + block_alloc;
+	p = xmalloc(st_add(sizeof(struct mp_block), block_alloc));
+	p->next_block = mem_pool->mp_block;
+	p->next_free = (char *)p->space;
+	p->end = p->next_free + block_alloc;
+	mem_pool->mp_block = p;
+
+	return p;
+}
+
+static void *mem_pool_alloc(struct mem_pool *mem_pool, size_t len)
 {
 	struct mp_block *p;
 	void *r;
@@ -645,21 +672,17 @@ static void *pool_alloc(size_t len)
 	if (len & (sizeof(uintmax_t) - 1))
 		len += sizeof(uintmax_t) - (len & (sizeof(uintmax_t) - 1));
 
-	for (p = mp_block_head; p; p = p->next_block)
-		if ((p->end - p->next_free >= len))
+	for (p = mem_pool->mp_block; p; p = p->next_block)
+		if (p->end - p->next_free >= len)
 			break;
 
 	if (!p) {
-		if (len >= (mem_pool_alloc/2)) {
-			total_allocd += len;
+		if (len >= (mem_pool->block_alloc / 2)) {
+			mem_pool->pool_alloc += len;
 			return xmalloc(len);
 		}
-		total_allocd += sizeof(struct mp_block) + mem_pool_alloc;
-		p = xmalloc(st_add(sizeof(struct mp_block), mem_pool_alloc));
-		p->next_block = mp_block_head;
-		p->next_free = (char *) p->space;
-		p->end = p->next_free + mem_pool_alloc;
-		mp_block_head = p;
+
+		p = mem_pool_alloc_block(mem_pool, mem_pool->block_alloc);
 	}
 
 	r = p->next_free;
@@ -667,10 +690,10 @@ static void *pool_alloc(size_t len)
 	return r;
 }
 
-static void *pool_calloc(size_t count, size_t size)
+static void *mem_pool_calloc(struct mem_pool *mem_pool, size_t count, size_t size)
 {
-	size_t len = count * size;
-	void *r = pool_alloc(len);
+	size_t len = st_mult(count, size);
+	void *r = mem_pool_alloc(mem_pool, len);
 	memset(r, 0, len);
 	return r;
 }
@@ -678,7 +701,7 @@ static void *pool_calloc(size_t count, size_t size)
 static char *pool_strdup(const char *s)
 {
 	size_t len = strlen(s) + 1;
-	char *r = pool_alloc(len);
+	char *r = mem_pool_alloc(&fi_mem_pool, len);
 	memcpy(r, s, len);
 	return r;
 }
@@ -687,7 +710,7 @@ static void insert_mark(uintmax_t idnum, struct object_entry *oe)
 {
 	struct mark_set *s = marks;
 	while ((idnum >> s->shift) >= 1024) {
-		s = pool_calloc(1, sizeof(struct mark_set));
+		s = mem_pool_calloc(&fi_mem_pool, 1, sizeof(struct mark_set));
 		s->shift = marks->shift + 10;
 		s->data.sets[0] = marks;
 		marks = s;
@@ -696,7 +719,7 @@ static void insert_mark(uintmax_t idnum, struct object_entry *oe)
 		uintmax_t i = idnum >> s->shift;
 		idnum -= i << s->shift;
 		if (!s->data.sets[i]) {
-			s->data.sets[i] = pool_calloc(1, sizeof(struct mark_set));
+			s->data.sets[i] = mem_pool_calloc(&fi_mem_pool, 1, sizeof(struct mark_set));
 			s->data.sets[i]->shift = s->shift - 10;
 		}
 		s = s->data.sets[i];
@@ -734,7 +757,7 @@ static struct atom_str *to_atom(const char *s, unsigned short len)
 		if (c->str_len == len && !strncmp(s, c->str_dat, len))
 			return c;
 
-	c = pool_alloc(sizeof(struct atom_str) + len + 1);
+	c = mem_pool_alloc(&fi_mem_pool, sizeof(struct atom_str) + len + 1);
 	c->str_len = len;
 	memcpy(c->str_dat, s, len);
 	c->str_dat[len] = 0;
@@ -765,7 +788,7 @@ static struct branch *new_branch(const char *name)
 	if (check_refname_format(name, REFNAME_ALLOW_ONELEVEL))
 		die("Branch name doesn't conform to GIT standards: %s", name);
 
-	b = pool_calloc(1, sizeof(struct branch));
+	b = mem_pool_calloc(&fi_mem_pool, 1, sizeof(struct branch));
 	b->name = pool_strdup(name);
 	b->table_next_branch = branch_table[hc];
 	b->branch_tree.versions[0].mode = S_IFDIR;
@@ -801,7 +824,7 @@ static struct tree_content *new_tree_content(unsigned int cnt)
 			avail_tree_table[hc] = f->next_avail;
 	} else {
 		cnt = cnt & 7 ? ((cnt / 8) + 1) * 8 : cnt;
-		f = pool_alloc(sizeof(*t) + sizeof(t->entries[0]) * cnt);
+		f = mem_pool_alloc(&fi_mem_pool, sizeof(*t) + sizeof(t->entries[0]) * cnt);
 		f->entry_capacity = cnt;
 	}
 
@@ -846,7 +869,7 @@ static struct tree_entry *new_tree_entry(void)
 
 	if (!avail_tree_entry) {
 		unsigned int n = tree_entry_alloc;
-		total_allocd += n * sizeof(struct tree_entry);
+		tree_entry_allocd += n * sizeof(struct tree_entry);
 		ALLOC_ARRAY(e, n);
 		avail_tree_entry = e;
 		while (n-- > 1) {
@@ -2867,7 +2890,7 @@ static void parse_new_tag(const char *arg)
 	enum object_type type;
 	const char *v;
 
-	t = pool_alloc(sizeof(struct tag));
+	t = mem_pool_alloc(&fi_mem_pool, sizeof(struct tag));
 	memset(t, 0, sizeof(struct tag));
 	t->name = pool_strdup(arg);
 	if (last_tag)
@@ -3466,12 +3489,12 @@ int cmd_main(int argc, const char **argv)
 	atom_table = xcalloc(atom_table_sz, sizeof(struct atom_str*));
 	branch_table = xcalloc(branch_table_sz, sizeof(struct branch*));
 	avail_tree_table = xcalloc(avail_tree_table_sz, sizeof(struct avail_tree_content*));
-	marks = pool_calloc(1, sizeof(struct mark_set));
+	marks = mem_pool_calloc(&fi_mem_pool, 1, sizeof(struct mark_set));
 
 	global_argc = argc;
 	global_argv = argv;
 
-	rc_free = pool_alloc(cmd_save * sizeof(*rc_free));
+	rc_free = mem_pool_alloc(&fi_mem_pool, cmd_save * sizeof(*rc_free));
 	for (i = 0; i < (cmd_save - 1); i++)
 		rc_free[i].next = &rc_free[i + 1];
 	rc_free[cmd_save - 1].next = NULL;
@@ -3545,8 +3568,8 @@ int cmd_main(int argc, const char **argv)
 		fprintf(stderr, "Total branches:  %10lu (%10lu loads     )\n", branch_count, branch_load_count);
 		fprintf(stderr, "      marks:     %10" PRIuMAX " (%10" PRIuMAX " unique    )\n", (((uintmax_t)1) << marks->shift) * 1024, marks_set_count);
 		fprintf(stderr, "      atoms:     %10u\n", atom_cnt);
-		fprintf(stderr, "Memory total:    %10" PRIuMAX " KiB\n", (total_allocd + alloc_count*sizeof(struct object_entry))/1024);
-		fprintf(stderr, "       pools:    %10lu KiB\n", (unsigned long)(total_allocd/1024));
+		fprintf(stderr, "Memory total:    %10" PRIuMAX " KiB\n", (tree_entry_allocd + fi_mem_pool.pool_alloc + alloc_count*sizeof(struct object_entry))/1024);
+		fprintf(stderr, "       pools:    %10lu KiB\n", (unsigned long)((tree_entry_allocd + fi_mem_pool.pool_alloc) /1024));
 		fprintf(stderr, "     objects:    %10" PRIuMAX " KiB\n", (alloc_count*sizeof(struct object_entry))/1024);
 		fprintf(stderr, "---------------------------------------------------------------------\n");
 		pack_report();
-- 
2.14.3