Merge branch 'mh/mmap-packed-refs'

Operations that do not touch (majority of) packed refs have been
optimized by making accesses to packed-refs file lazy; we no longer
pre-parse everything, and an access to a single ref in the
packed-refs does not touch majority of irrelevant refs, either.

* mh/mmap-packed-refs: (21 commits)
  packed-backend.c: rename a bunch of things and update comments
  mmapped_ref_iterator: inline into `packed_ref_iterator`
  ref_cache: remove support for storing peeled values
  packed_ref_store: get rid of the `ref_cache` entirely
  ref_store: implement `refs_peel_ref()` generically
  packed_read_raw_ref(): read the reference from the mmapped buffer
  packed_ref_iterator_begin(): iterate using `mmapped_ref_iterator`
  read_packed_refs(): ensure that references are ordered when read
  packed_ref_cache: keep the `packed-refs` file mmapped if possible
  packed-backend.c: reorder some definitions
  mmapped_ref_iterator_advance(): no peeled value for broken refs
  mmapped_ref_iterator: add iterator over a packed-refs file
  packed_ref_cache: remember the file-wide peeling state
  read_packed_refs(): read references with minimal copying
  read_packed_refs(): make parsing of the header line more robust
  read_packed_refs(): only check for a header at the top of the file
  read_packed_refs(): use mmap to read the `packed-refs` file
  die_unterminated_line(), die_invalid_line(): new functions
  packed_ref_cache: add a backlink to the associated `packed_ref_store`
  prefix_ref_iterator: break when we leave the prefix
  ...

1 files changed, 10 insertions, 45 deletions

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 4b46cd2e26..1b6141e718 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -641,43 +641,6 @@ out:
 	return ret;
 }
 
-static int files_peel_ref(struct ref_store *ref_store,
-			  const char *refname, unsigned char *sha1)
-{
-	struct files_ref_store *refs =
-		files_downcast(ref_store, REF_STORE_READ | REF_STORE_ODB,
-			       "peel_ref");
-	int flag;
-	unsigned char base[20];
-
-	if (current_ref_iter && current_ref_iter->refname == refname) {
-		struct object_id peeled;
-
-		if (ref_iterator_peel(current_ref_iter, &peeled))
-			return -1;
-		hashcpy(sha1, peeled.hash);
-		return 0;
-	}
-
-	if (refs_read_ref_full(ref_store, refname,
-			       RESOLVE_REF_READING, base, &flag))
-		return -1;
-
-	/*
-	 * If the reference is packed, read its ref_entry from the
-	 * cache in the hope that we already know its peeled value.
-	 * We only try this optimization on packed references because
-	 * (a) forcing the filling of the loose reference cache could
-	 * be expensive and (b) loose references anyway usually do not
-	 * have REF_KNOWS_PEELED.
-	 */
-	if (flag & REF_ISPACKED &&
-	    !refs_peel_ref(refs->packed_ref_store, refname, sha1))
-		return 0;
-
-	return peel_object(base, sha1);
-}
-
 struct files_ref_iterator {
 	struct ref_iterator base;
 
@@ -748,7 +711,7 @@ static struct ref_iterator *files_ref_iterator_begin(
 		const char *prefix, unsigned int flags)
 {
 	struct files_ref_store *refs;
-	struct ref_iterator *loose_iter, *packed_iter;
+	struct ref_iterator *loose_iter, *packed_iter, *overlay_iter;
 	struct files_ref_iterator *iter;
 	struct ref_iterator *ref_iterator;
 	unsigned int required_flags = REF_STORE_READ;
@@ -758,10 +721,6 @@ static struct ref_iterator *files_ref_iterator_begin(
 
 	refs = files_downcast(ref_store, required_flags, "ref_iterator_begin");
 
-	iter = xcalloc(1, sizeof(*iter));
-	ref_iterator = &iter->base;
-	base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable);
-
 	/*
 	 * We must make sure that all loose refs are read before
 	 * accessing the packed-refs file; this avoids a race
@@ -797,7 +756,13 @@ static struct ref_iterator *files_ref_iterator_begin(
 			refs->packed_ref_store, prefix, 0,
 			DO_FOR_EACH_INCLUDE_BROKEN);
 
-	iter->iter0 = overlay_ref_iterator_begin(loose_iter, packed_iter);
+	overlay_iter = overlay_ref_iterator_begin(loose_iter, packed_iter);
+
+	iter = xcalloc(1, sizeof(*iter));
+	ref_iterator = &iter->base;
+	base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable,
+			       overlay_iter->ordered);
+	iter->iter0 = overlay_iter;
 	iter->flags = flags;
 
 	return ref_iterator;
@@ -2094,7 +2059,7 @@ static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
 	struct ref_iterator *ref_iterator = &iter->base;
 	struct strbuf sb = STRBUF_INIT;
 
-	base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
+	base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
 	strbuf_addf(&sb, "%s/logs", gitdir);
 	iter->dir_iterator = dir_iterator_begin(sb.buf);
 	iter->ref_store = ref_store;
@@ -2138,6 +2103,7 @@ static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_st
 		return reflog_iterator_begin(ref_store, refs->gitcommondir);
 	} else {
 		return merge_ref_iterator_begin(
+			0,
 			reflog_iterator_begin(ref_store, refs->gitdir),
 			reflog_iterator_begin(ref_store, refs->gitcommondir),
 			reflog_iterator_select, refs);
@@ -3089,7 +3055,6 @@ struct ref_storage_be refs_be_files = {
 	files_initial_transaction_commit,
 
 	files_pack_refs,
-	files_peel_ref,
 	files_create_symref,
 	files_delete_refs,
 	files_rename_ref,