From 42eca38f51d0dd5af50d0e97685c04ac5f621468 Mon Sep 17 00:00:00 2001 From: Arijit Banerjee Date: Thu, 28 May 2026 14:59:28 -0700 Subject: [PATCH] index-pack: retain child bases in delta cache When resolving a delta whose result has children of its own, index-pack adds the result to work_head, accounts its data in base_cache_used, and calls prune_base_data(). It then immediately frees that same data. This bypasses the existing delta base cache policy and can force later descendants to reconstruct the queued base again. Let the existing delta_base_cache_limit pruning policy decide whether to keep or evict the data instead. This does not add a new cache or increase the cache limit. The object data is already accounted in base_cache_used before prune_base_data() runs, and the existing pruning and base cleanup paths still release it. On a quiet Ubuntu 24.04 VM with 16 vCPUs, 32 GiB RAM, and local SSD, direct index-pack timings on single-pack Linux fixtures improved as follows: linux blobless: 69.17s -> 57.98s (16.2% faster), RSS flat linux full: 280.72s -> 236.32s (15.8% faster), RSS +1.9% Five-repeat medians on public repositories also improved: git.git: 12.31s -> 10.70s (13.1% faster) libgit2: 3.35s -> 2.88s (14.0% faster) redis: 6.52s -> 5.64s (13.5% faster) cpython: 33.02s -> 31.44s (4.8% faster) The standard p5302 perf test on a smaller git.git fixture was neutral: 5302.9 index-pack default threads: 11.21(38.07+1.33) -> 11.16(37.90+1.31), -0.4% t/t5302-pack-index.sh passed, and GitGitGadget's linux-leaks CI also exercised that test under SANITIZE=leak. Signed-off-by: Arijit Banerjee --- builtin/index-pack.c | 1 - 1 file changed, 1 deletion(-) diff --git a/builtin/index-pack.c b/builtin/index-pack.c index cf0bd8280dca83..027c64b522ebb2 100644 --- a/builtin/index-pack.c +++ b/builtin/index-pack.c @@ -1212,7 +1212,6 @@ static void *threaded_second_pass(void *data) list_add(&child->list, &work_head); base_cache_used += child->size; prune_base_data(NULL); - free_base_data(child); } else if (child) { /* * This child does not have its own children. It may be