On Mon, Apr 12, 2021 at 07:47:41PM -0400, Jeff King wrote:
> The patch below drops the peak heap to 165MB. Still quite a bit more,
> but I think it's a combination of delta-base cache (96MB) plus extra
> structs for all the non-commit objects whose flags we marked.
I think we can do even better than that, after looking into the "do we
really need to parse the objects?" comment I left (spoiler: the answer
is no, we do not need to, at least for that caller).
Here are some cleaned-up patches that I think improve the situation
quite a bit. This is just the low-hanging fruit from this part of the
discussion; I'm sure there's more to do to make using partial clones
pleasant. In particular:
- this does nothing for the "oops, we turned all of the promisor
objects loose and then deleted them" problem. Hopefully Rafael
will produce a nice patch for that
- In is_promisor_object(), we still call parse_object(), because it
really does look at the contents. But doing so for blobs is wasteful
(it's a lot of bytes we push through sha1, and we don't even look at
them). It might be worth using oid_object_info() to avoid this. This
introduces a little overhead, but I think would be a net win (it
would be really nice if we could amortize the object lookup work;
i.e., if there was a way to call oid_object_info_extended() and say
"open the object and look at the type; only return the contents if
it's a non-blob").
- I still think it's probably worth having a mode where we store the
set of pointed-to objects we don't have, rather than parsing on the
fly. This could easily be made optional (it's a good thing if you
_have_ a lot of objects that point to a small or moderate number of
missing objects, like a blob:limit or blob:none filter; it's a bad
thing if you have very few objects but they point to a very large
number).
I didn't explore any of those here, and I don't plan to look into them
anytime soon. I'm just documenting my findings for later.
Anyway, here are the patches.
[1/3]: is_promisor_object(): free tree buffer after parsing
[2/3]: lookup_unknown_object(): take a repository argument
[3/3]: revision: avoid parsing with --exclude-promisor-objects
builtin/fsck.c | 2 +-
builtin/pack-objects.c | 2 +-
http-push.c | 2 +-
object.c | 7 +++----
object.h | 2 +-
packfile.c | 1 +
refs.c | 2 +-
revision.c | 2 +-
t/helper/test-example-decorate.c | 6 +++---
t/perf/p5600-partial-clone.sh | 12 ++++++++++++
upload-pack.c | 2 +-
walker.c | 2 +-
12 files changed, 27 insertions(+), 15 deletions(-)
-Peff
