From: Ben Peart Date: Tue, 09 Oct 2018 14:48:34 GMT Subject: Re: [PATCH] unpack-trees: allow missing CE_SKIP_WORKTREE objs Message-ID: <7ac4ea1d-596d-cffd-337f-bf1879d982e1@gmail.com> In-Reply-To: <20181008214816.42856-1-jonathantanmy@google.com> On 10/8/2018 5:48 PM, Jonathan Tan wrote: > Whenever a sparse checkout occurs, the existence of all blobs in the > index is verified, whether or not they are included or excluded by the > .git/info/sparse-checkout specification. This degrades performance, > significantly in the case of a partial clone, because a lazy fetch > occurs whenever the existence of a missing blob is checked. > > At the point of invoking cache_tree_update() in unpack_trees(), > CE_SKIP_WORKTREE is already set on all excluded blobs > (mark_new_skip_worktree() is called twice to set CE_NEW_SKIP_WORKTREE, > then apply_sparse_checkout() is called which copies over > CE_NEW_SKIP_WORKTREE to CE_SKIP_WORKTREE). cache_tree_update() can use > this information to know which blobs are excluded, and thus skip the > checking of these. > > Because cache_tree_update() is used from multiple places, this new > behavior is guarded by a new flag WRITE_TREE_SKIP_WORKTREE_MISSING_OK. > Implement this new flag, and teach unpack_trees() to invoke > cache_tree_update() with this new flag. > I wonder if preventing the download of all missing blobs should be limited to only the checkout command. When you looked at the other places that call cache_tree_update(), does it make sense that they trigger the download of all the missing blobs? For example, I suspect you would not want them all downloaded just to do a merge-recursive. In full disclosure, we implemented this a couple of years ago [1] for GVFS and opted to do the logic a little differently. We found that we didn't want to trigger the download of all missing blobs in cache_tree_update() for _any_ command that was executing in a partially cloned repo. This is safe because if any individual blob is actually needed, it will get downloaded "on demand" already. [1] https://github.com/Microsoft/git/commit/ec865500d98 > Signed-off-by: Jonathan Tan > --- > cache-tree.c | 6 +++++- > cache-tree.h | 4 ++++ > t/t1090-sparse-checkout-scope.sh | 33 ++++++++++++++++++++++++++++++++ > unpack-trees.c | 1 + > 4 files changed, 43 insertions(+), 1 deletion(-) > > diff --git a/cache-tree.c b/cache-tree.c > index 5ce51468f0..340caf2d34 100644 > --- a/cache-tree.c > +++ b/cache-tree.c > @@ -246,6 +246,8 @@ static int update_one(struct cache_tree *it, > int missing_ok = flags & WRITE_TREE_MISSING_OK; > int dryrun = flags & WRITE_TREE_DRY_RUN; > int repair = flags & WRITE_TREE_REPAIR; > + int skip_worktree_missing_ok = > + flags & WRITE_TREE_SKIP_WORKTREE_MISSING_OK; > int to_invalidate = 0; > int i; > > @@ -356,7 +358,9 @@ static int update_one(struct cache_tree *it, > } > > if (is_null_oid(oid) || > - (mode != S_IFGITLINK && !missing_ok && !has_object_file(oid))) { > + (mode != S_IFGITLINK && !missing_ok && > + !(skip_worktree_missing_ok && ce_skip_worktree(ce)) && > + !has_object_file(oid))) { > strbuf_release(&buffer); > if (expected_missing) > return -1; > diff --git a/cache-tree.h b/cache-tree.h > index 0ab6784ffe..655d487619 100644 > --- a/cache-tree.h > +++ b/cache-tree.h > @@ -40,6 +40,10 @@ void cache_tree_verify(struct index_state *); > #define WRITE_TREE_DRY_RUN 4 > #define WRITE_TREE_SILENT 8 > #define WRITE_TREE_REPAIR 16 > +/* > + * Do not check for the presence of cache entry objects with CE_SKIP_WORKTREE. > + */ > +#define WRITE_TREE_SKIP_WORKTREE_MISSING_OK 32 > > /* error return codes */ > #define WRITE_TREE_UNREADABLE_INDEX (-1) > diff --git a/t/t1090-sparse-checkout-scope.sh b/t/t1090-sparse-checkout-scope.sh > index 25d7c700f6..090b7fc3d3 100755 > --- a/t/t1090-sparse-checkout-scope.sh > +++ b/t/t1090-sparse-checkout-scope.sh > @@ -63,4 +63,37 @@ test_expect_success 'return to full checkout of master' ' > test "$(cat b)" = "modified" > ' > > +test_expect_success 'in partial clone, sparse checkout only fetches needed blobs' ' > + test_create_repo server && > + git clone "file://$(pwd)/server" client && > + > + test_config -C server uploadpack.allowfilter 1 && > + test_config -C server uploadpack.allowanysha1inwant 1 && > + echo a >server/a && > + echo bb >server/b && > + mkdir server/c && > + echo ccc >server/c/c && > + git -C server add a b c/c && > + git -C server commit -m message && > + > + test_config -C client core.sparsecheckout 1 && > + test_config -C client extensions.partialclone origin && > + echo "!/*" >client/.git/info/sparse-checkout && > + echo "/a" >>client/.git/info/sparse-checkout && > + git -C client fetch --filter=blob:none origin && > + git -C client checkout FETCH_HEAD && > + > + git -C client rev-list HEAD \ > + --quiet --objects --missing=print >unsorted_actual && > + ( > + printf "?" && > + git hash-object server/b && > + printf "?" && > + git hash-object server/c/c > + ) >unsorted_expect && > + sort unsorted_actual >actual && > + sort unsorted_expect >expect && > + test_cmp expect actual > +' > + > test_done > diff --git a/unpack-trees.c b/unpack-trees.c > index 51bfac6aa0..39e0e7a6c7 100644 > --- a/unpack-trees.c > +++ b/unpack-trees.c > @@ -1635,6 +1635,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options > o->result.cache_tree = cache_tree(); > if (!cache_tree_fully_valid(o->result.cache_tree)) > cache_tree_update(&o->result, > + WRITE_TREE_SKIP_WORKTREE_MISSING_OK | > WRITE_TREE_SILENT | > WRITE_TREE_REPAIR); > } >