We only cache deltas when it's smaller than a certain limit. This limit
defaults to 1000 but save its compressed length in a 64-bit field.
Shrink that field down to 16 bits, so you can only cache 65kb deltas.
Larger deltas must be recomputed at when the pack is written down.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx>
---
Documentation/config.txt | 3 ++-
builtin/pack-objects.c | 22 ++++++++++++++++------
pack-objects.h | 3 ++-
3 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/Documentation/config.txt b/Documentation/config.txt
index 9bd3f5a789..00fa824448 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -2449,7 +2449,8 @@ pack.deltaCacheLimit::
The maximum size of a delta, that is cached in
linkgit:git-pack-objects[1]. This cache is used to speed up the
writing object phase by not having to recompute the final delta
- result once the best match for all objects is found. Defaults to 1000.
+ result once the best match for all objects is found.
+ Defaults to 1000. Maximum value is 65535.
pack.threads::
Specifies the number of threads to spawn when searching for best
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index f7d3f6a1a8..b3e19815f1 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -2100,12 +2100,19 @@ static void find_deltas(struct object_entry **list, unsigned *list_size,
* between writes at that moment.
*/
if (entry->delta_data && !pack_to_stdout) {
- entry->z_delta_size = do_compress(&entry->delta_data,
- entry->delta_size);
- cache_lock();
- delta_cache_size -= entry->delta_size;
- delta_cache_size += entry->z_delta_size;
- cache_unlock();
+ unsigned long size;
+
+ size = do_compress(&entry->delta_data, entry->delta_size);
+ if (size < (1 << OE_Z_DELTA_BITS)) {
+ entry->z_delta_size = size;
+ cache_lock();
+ delta_cache_size -= entry->delta_size;
+ delta_cache_size += entry->z_delta_size;
+ cache_unlock();
+ } else {
+ FREE_AND_NULL(entry->delta_data);
+ entry->z_delta_size = 0;
+ }
}
/* if we made n a delta, and if n is already at max
@@ -3084,6 +3091,9 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
if (depth >= (1 << OE_DEPTH_BITS))
die(_("delta chain depth %d is greater than maximum limit %d"),
depth, (1 << OE_DEPTH_BITS) - 1);
+ if (cache_max_small_delta_size >= (1 << OE_Z_DELTA_BITS))
+ die(_("pack.deltaCacheLimit is greater than maximum limit %d"),
+ (1 << OE_Z_DELTA_BITS) - 1);
argv_array_push(&rp, "pack-objects");
if (thin) {
diff --git a/pack-objects.h b/pack-objects.h
index 433c194ffe..415b961245 100644
--- a/pack-objects.h
+++ b/pack-objects.h
@@ -4,6 +4,7 @@
#define OE_DFS_STATE_BITS 2
#define OE_DEPTH_BITS 12
#define OE_IN_PACK_BITS 10
+#define OE_Z_DELTA_BITS 16
/*
* State flags for depth-first search used for analyzing delta cycles.
@@ -79,7 +80,7 @@ struct object_entry {
*/
void *delta_data; /* cached delta (uncompressed) */
unsigned long delta_size; /* delta data size (uncompressed) */
- unsigned long z_delta_size; /* delta data size (compressed) */
+ unsigned z_delta_size:OE_Z_DELTA_BITS;
unsigned type_:TYPE_BITS;
unsigned in_pack_type:TYPE_BITS; /* could be delta */
unsigned type_valid:1;
--
2.17.0.rc0.348.gd5a49e0b6f
