config: make delta_base_cache_limit a non-global variable

The `delta_base_cache_limit` variable is a global config variable used
by multiple subsystems. Let's make this non-global, by adding this
variable to the stack of each of the subsystems where it is used.

In `gc.c` we add it to the `gc_config` struct and also the constructor
function. In `index-pack.c` we add it to the `pack_idx_option` struct
and its constructor. Finally, in `packfile.c` we dynamically retrieve
this value from the repository config, since the value is only used once
in the entire subsystem.

These changes are made to remove the usage of `delta_base_cache_limit`
as a global variable in `packfile.c`. This brings us one step closer to
removing the `USE_THE_REPOSITORY_VARIABLE` definition in `packfile.c`
which we complete in the next patch.

Signed-off-by: Karthik Nayak <[email protected]>
Signed-off-by: Taylor Blau <[email protected]>

Author: KarthikNayak

builtin/gc.c

@@ -138,6 +138,7 @@ struct gc_config {
 	char *repack_filter_to;
 	unsigned long big_pack_threshold;
 	unsigned long max_delta_cache_size;
+	unsigned long delta_base_cache_limit;
 };
 
 #define GC_CONFIG_INIT { \
@@ -153,6 +154,7 @@ struct gc_config {
 	.prune_expire = xstrdup("2.weeks.ago"), \
 	.prune_worktrees_expire = xstrdup("3.months.ago"), \
 	.max_delta_cache_size = DEFAULT_DELTA_CACHE_SIZE, \
+	.delta_base_cache_limit = DEFAULT_DELTA_BASE_CACHE_LIMIT, \
 }
 
 static void gc_config_release(struct gc_config *cfg)
@@ -205,6 +207,7 @@ static void gc_config(struct gc_config *cfg)
 
 	git_config_get_ulong("gc.bigpackthreshold", &cfg->big_pack_threshold);
 	git_config_get_ulong("pack.deltacachesize", &cfg->max_delta_cache_size);
+	git_config_get_ulong("core.deltabasecachelimit", &cfg->delta_base_cache_limit);
 
 	if (!git_config_get_string("gc.repackfilter", &owned)) {
 		free(cfg->repack_filter);
@@ -416,7 +419,7 @@ static uint64_t estimate_repack_memory(struct gc_config *cfg,
 	 * read_sha1_file() (either at delta calculation phase, or
 	 * writing phase) also fills up the delta base cache
 	 */
-	heap += delta_base_cache_limit;
+	heap += cfg->delta_base_cache_limit;
 	/* and of course pack-objects has its own delta cache */
 	heap += cfg->max_delta_cache_size;
 

builtin/index-pack.c

@@ -1238,7 +1238,7 @@ static void parse_pack_objects(unsigned char *hash)
  *   recursively checking if the resulting object is used as a base
  *   for some more deltas.
  */
-static void resolve_deltas(void)
+static void resolve_deltas(struct pack_idx_option *opts)
 {
 	int i;
 
@@ -1254,7 +1254,7 @@ static void resolve_deltas(void)
 					  nr_ref_deltas + nr_ofs_deltas);
 
 	nr_dispatched = 0;
-	base_cache_limit = delta_base_cache_limit * nr_threads;
+	base_cache_limit = opts->delta_base_cache_limit * nr_threads;
 	if (nr_threads > 1 || getenv("GIT_FORCE_THREADS")) {
 		init_thread();
 		work_lock();
@@ -1604,6 +1604,10 @@ static int git_index_pack_config(const char *k, const char *v,
 		else
 			opts->flags &= ~WRITE_REV;
 	}
+	if (!strcmp(k, "core.deltabasecachelimit")) {
+		opts->delta_base_cache_limit = git_config_ulong(k, v, ctx->kvi);
+		return 0;
+	}
 	return git_default_config(k, v, ctx, cb);
 }
 
@@ -1930,7 +1934,7 @@ int cmd_index_pack(int argc,
 	parse_pack_objects(pack_hash);
 	if (report_end_of_input)
 		write_in_full(2, "\0", 1);
-	resolve_deltas();
+	resolve_deltas(&opts);
 	conclude_pack(fix_thin_pack, curr_pack, pack_hash);
 	free(ofs_deltas);
 	free(ref_deltas);

config.c

@@ -1515,11 +1515,6 @@ static int git_default_core_config(const char *var, const char *value,
 		return 0;
 	}
 
-	if (!strcmp(var, "core.deltabasecachelimit")) {
-		delta_base_cache_limit = git_config_ulong(var, value, ctx->kvi);
-		return 0;
-	}
-
 	if (!strcmp(var, "core.autocrlf")) {
 		if (value && !strcasecmp(value, "input")) {
 			auto_crlf = AUTO_CRLF_INPUT;

environment.c

@@ -51,7 +51,6 @@ enum fsync_method fsync_method = FSYNC_METHOD_DEFAULT;
 enum fsync_component fsync_components = FSYNC_COMPONENTS_DEFAULT;
 size_t packed_git_window_size = DEFAULT_PACKED_GIT_WINDOW_SIZE;
 size_t packed_git_limit = DEFAULT_PACKED_GIT_LIMIT;
-size_t delta_base_cache_limit = 96 * 1024 * 1024;
 unsigned long big_file_threshold = 512 * 1024 * 1024;
 char *editor_program;
 char *askpass_program;

environment.h

@@ -165,7 +165,6 @@ extern int zlib_compression_level;
 extern int pack_compression_level;
 extern size_t packed_git_window_size;
 extern size_t packed_git_limit;
-extern size_t delta_base_cache_limit;
 extern unsigned long big_file_threshold;
 extern unsigned long pack_size_limit_cfg;
 extern int max_allowed_tree_depth;

pack-objects.h

@@ -7,7 +7,8 @@
 
 struct repository;
 
-#define DEFAULT_DELTA_CACHE_SIZE (256 * 1024 * 1024)
+#define DEFAULT_DELTA_CACHE_SIZE       (256 * 1024 * 1024)
+#define DEFAULT_DELTA_BASE_CACHE_LIMIT (96 * 1024 * 1024)
 
 #define OE_DFS_STATE_BITS	2
 #define OE_DEPTH_BITS		12

pack-write.c

@@ -21,6 +21,7 @@ void reset_pack_idx_option(struct pack_idx_option *opts)
 	memset(opts, 0, sizeof(*opts));
 	opts->version = 2;
 	opts->off32_limit = 0x7fffffff;
+	opts->delta_base_cache_limit = DEFAULT_DELTA_BASE_CACHE_LIMIT;
 }
 
 static int sha1_compare(const void *_a, const void *_b)

pack.h

@@ -58,6 +58,7 @@ struct pack_idx_option {
 	 */
 	int anomaly_alloc, anomaly_nr;
 	uint32_t *anomaly;
+	unsigned long delta_base_cache_limit;
 };
 
 void reset_pack_idx_option(struct pack_idx_option *);

packfile.c

@@ -24,6 +24,8 @@
 #include "commit-graph.h"
 #include "pack-revindex.h"
 #include "promisor-remote.h"
+#include "config.h"
+#include "pack-objects.h"
 
 char *odb_pack_name(struct repository *r, struct strbuf *buf,
 		    const unsigned char *hash, const char *ext)
@@ -1496,7 +1498,9 @@ void clear_delta_base_cache(void)
 }
 
 static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
-	void *base, unsigned long base_size, enum object_type type)
+				 void *base, unsigned long base_size,
+				 unsigned long delta_base_cache_limit,
+				 enum object_type type)
 {
 	struct delta_base_cache_entry *ent;
 	struct list_head *lru, *tmp;
@@ -1697,6 +1701,9 @@ void *unpack_entry(struct repository *r, struct packed_git *p, off_t obj_offset,
 	struct unpack_entry_stack_ent *delta_stack = small_delta_stack;
 	int delta_stack_nr = 0, delta_stack_alloc = UNPACK_ENTRY_STACK_PREALLOC;
 	int base_from_cache = 0;
+	unsigned long delta_base_cache_limit = DEFAULT_DELTA_BASE_CACHE_LIMIT;
+
+	repo_config_get_ulong(r, "core.deltabasecachelimit", &delta_base_cache_limit);
 
 	write_pack_access_log(p, obj_offset);
 
@@ -1878,7 +1885,9 @@ void *unpack_entry(struct repository *r, struct packed_git *p, off_t obj_offset,
 		 * before we are done using it.
 		 */
 		if (!external_base)
-			add_delta_base_cache(p, base_obj_offset, base, base_size, type);
+			add_delta_base_cache(p, base_obj_offset, base,
+					     base_size, delta_base_cache_limit,
+					     type);
 
 		free(delta_data);
 		free(external_base);