diff options
Diffstat (limited to '_support/git-patches/v2.35.1.gl1/0039-refs-files-backend-optimize-reading-of-symbolic-refs.patch')
| -rw-r--r-- | _support/git-patches/v2.35.1.gl1/0039-refs-files-backend-optimize-reading-of-symbolic-refs.patch | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/_support/git-patches/v2.35.1.gl1/0039-refs-files-backend-optimize-reading-of-symbolic-refs.patch b/_support/git-patches/v2.35.1.gl1/0039-refs-files-backend-optimize-reading-of-symbolic-refs.patch new file mode 100644 index 000000000..465257950 --- /dev/null +++ b/_support/git-patches/v2.35.1.gl1/0039-refs-files-backend-optimize-reading-of-symbolic-refs.patch @@ -0,0 +1,122 @@ +From 0a7b38707d5d5c8a7baeb88a85d6259cee4f4e4d Mon Sep 17 00:00:00 2001 +Message-Id: <0a7b38707d5d5c8a7baeb88a85d6259cee4f4e4d.1647334703.git.ps@pks.im> +In-Reply-To: <4de656263aa195080495fc0a103351b9eaac8160.1647334702.git.ps@pks.im> +References: <4de656263aa195080495fc0a103351b9eaac8160.1647334702.git.ps@pks.im> +From: Patrick Steinhardt <ps@pks.im> +Date: Tue, 1 Mar 2022 10:33:54 +0100 +Subject: [PATCH 39/39] refs/files-backend: optimize reading of symbolic refs +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +When reading references via `files_read_raw_ref()` we always consult +both the loose reference, and if that wasn't found, we also consult the +packed-refs file. While this makes sense to read a generic reference, it +is wasteful in the case where we only care about symbolic references: +the packed-refs backend does not support them, and thus it cannot ever +return one for us. + +Special-case reading of symbolic references for the files backend such +that we always skip asking the packed-refs backend. + +We use `refs_read_symbolic_ref()` extensively to determine whether we +need to skip updating local symbolic references during a fetch, which is +why the change results in a significant speedup when doing fetches in +repositories with huge numbers of references. The following benchmark +executes a mirror-fetch in a repository with about 2 million references +via `git fetch --prune --no-write-fetch-head +refs/*:refs/*`: + + Benchmark 1: HEAD~ + Time (mean ± σ): 68.372 s ± 2.344 s [User: 65.629 s, System: 8.786 s] + Range (min … max): 65.745 s … 70.246 s 3 runs + + Benchmark 2: HEAD + Time (mean ± σ): 60.259 s ± 0.343 s [User: 61.019 s, System: 7.245 s] + Range (min … max): 60.003 s … 60.649 s 3 runs + + Summary + 'HEAD' ran + 1.13 ± 0.04 times faster than 'HEAD~' + +Signed-off-by: Patrick Steinhardt <ps@pks.im> +Signed-off-by: Junio C Hamano <gitster@pobox.com> +--- + refs/files-backend.c | 34 ++++++++++++++++++++++++++++------ + 1 file changed, 28 insertions(+), 6 deletions(-) + +diff --git a/refs/files-backend.c b/refs/files-backend.c +index f3428a9f12..0457ecdb42 100644 +--- a/refs/files-backend.c ++++ b/refs/files-backend.c +@@ -338,9 +338,9 @@ static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs) + return refs->loose; + } + +-static int files_read_raw_ref(struct ref_store *ref_store, const char *refname, +- struct object_id *oid, struct strbuf *referent, +- unsigned int *type, int *failure_errno) ++static int read_ref_internal(struct ref_store *ref_store, const char *refname, ++ struct object_id *oid, struct strbuf *referent, ++ unsigned int *type, int *failure_errno, int skip_packed_refs) + { + struct files_ref_store *refs = + files_downcast(ref_store, REF_STORE_READ, "read_raw_ref"); +@@ -381,7 +381,7 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname, + if (lstat(path, &st) < 0) { + int ignore_errno; + myerr = errno; +- if (myerr != ENOENT) ++ if (myerr != ENOENT || skip_packed_refs) + goto out; + if (refs_read_raw_ref(refs->packed_ref_store, refname, oid, + referent, type, &ignore_errno)) { +@@ -425,7 +425,8 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname, + * ref is supposed to be, there could still be a + * packed ref: + */ +- if (refs_read_raw_ref(refs->packed_ref_store, refname, oid, ++ if (skip_packed_refs || ++ refs_read_raw_ref(refs->packed_ref_store, refname, oid, + referent, type, &ignore_errno)) { + myerr = EISDIR; + goto out; +@@ -470,6 +471,27 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname, + return ret; + } + ++static int files_read_raw_ref(struct ref_store *ref_store, const char *refname, ++ struct object_id *oid, struct strbuf *referent, ++ unsigned int *type, int *failure_errno) ++{ ++ return read_ref_internal(ref_store, refname, oid, referent, type, failure_errno, 0); ++} ++ ++static int files_read_symbolic_ref(struct ref_store *ref_store, const char *refname, ++ struct strbuf *referent) ++{ ++ struct object_id oid; ++ int failure_errno, ret; ++ unsigned int type; ++ ++ ret = read_ref_internal(ref_store, refname, &oid, referent, &type, &failure_errno, 1); ++ if (ret) ++ return ret; ++ ++ return !(type & REF_ISSYMREF); ++} ++ + int parse_loose_ref_contents(const char *buf, struct object_id *oid, + struct strbuf *referent, unsigned int *type, + int *failure_errno) +@@ -3286,7 +3308,7 @@ struct ref_storage_be refs_be_files = { + + files_ref_iterator_begin, + files_read_raw_ref, +- NULL, ++ files_read_symbolic_ref, + + files_reflog_iterator_begin, + files_for_each_reflog_ent, +-- +2.35.1 + |