[PATCH 09/15] pack-objects: shrink z_delta_size field in struct object_entry
- From
Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
- Date
- Apr 14, 2018, 15:35 UTC
- Message-ID
- <20180414153513.9902-10-pclouds@gmail.com>
- In-Reply-To
- <20180414153513.9902-1-pclouds@gmail.com>
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 20 bits, so you can only cache 1MB deltas. Larger deltas must be recomputed at when the pack is written down.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> --- Documentation/config.txt | 3 ++- builtin/pack-objects.c | 24 ++++++++++++++++++------ pack-objects.h | 3 ++- 3 files changed, 22 insertions(+), 8 deletions(-)
diff --git a/Documentation/config.txt b/Documentation/config.txt index d97f10722c..a62134264e 100644 --- a/Documentation/config.txt +++ b/Documentation/config.txt @@ -2459,7 +2459,8 @@ 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 ec02641d2e..211bb1ad0e 100644 --- a/builtin/pack-objects.c +++ b/builtin/pack-objects.c @@ -2099,12 +2099,19 @@ 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 < (1U << 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 @@ -3087,6 +3094,11 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) depth, (1 << OE_DEPTH_BITS) - 1); depth = (1 << OE_DEPTH_BITS) - 1; } + if (cache_max_small_delta_size >= (1U << OE_Z_DELTA_BITS)) { + warning(_("pack.deltaCacheLimit is too high, forcing %d"), + (1U << OE_Z_DELTA_BITS) - 1); + cache_max_small_delta_size = (1U << OE_Z_DELTA_BITS) - 1; + } argv_array_push(&rp, "pack-objects"); if (thin) { diff --git a/pack-objects.h b/pack-objects.h index e962dce3c0..9d0391c173 100644 --- a/pack-objects.h +++ b/pack-objects.h @@ -6,6 +6,7 @@ #define OE_DFS_STATE_BITS 2 #define OE_DEPTH_BITS 12 #define OE_IN_PACK_BITS 10 +#define OE_Z_DELTA_BITS 20 /* * State flags for depth-first search used for analyzing delta cycles. @@ -77,7 +78,7 @@ 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;
-- 2.17.0.367.g5dd2e386c3