Skip to content

Compilation_unit optimisations #1035

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged

Conversation

mshinwell
Copy link
Collaborator

@mshinwell mshinwell commented Dec 23, 2022

There is a problem with build artifact size at tag 4.14.0-0. All *.cm* files are about 25% bigger on the JS tree build under Closure. Much of this comes from the types used to represent cmi and cmx imports; we had to change these for the functor packs work (and in any case they weren't very efficient, marshalling as lists rather than arrays for example). We think there might also be some other changes causing cmi files to be larger, but will look at those later.

We have two changes to make to rectify this problem. This is the first, which uses an Obj trick to significantly improve the memory layout of values of type Compilation_unit.t (and makes sure that sharing isn't broken by functions like full_path_as_string). It seems likely that we will be able to remove this in due course given work on similar kinds of unboxing going on elsewhere.

The second replaces the tuple types that are scattered around the codebase with a single Import_info.t type which is abstract and whose memory layout is much better. This will be posted as a separate PR.

Joint work with @xclerc .

Includes #1034.

@mshinwell mshinwell changed the title Compilation unit optimisations Compilation_unit optimisations Dec 23, 2022
@mshinwell mshinwell mentioned this pull request Dec 23, 2022
Copy link
Contributor

@xclerc xclerc left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Using Obj here will be controversial,
but the size improvements are quite
probably worth the risk.

All comments below are minor and
can be safely ignored.

@mshinwell mshinwell merged commit 18c139c into ocaml-flambda:main Dec 27, 2022
mshinwell added a commit that referenced this pull request Dec 27, 2022
mshinwell added a commit to mshinwell/flambda-backend that referenced this pull request Dec 28, 2022
b11eea1 flambda-backend: Introduce Import_info (ocaml-flambda#1036)
bc5b135 flambda-backend: Fix `ocamlobjinfo` on flambda2 .cmx files (ocaml-flambda#1029)
c8babbd flambda-backend: Compilation_unit optimisations (ocaml-flambda#1035)
e8d3e22 flambda-backend: Use 4.14.0 opam switch for building (includes upgrading ocamlformat to 0.24.1) (ocaml-flambda#1030)
eb14a86 flambda-backend: Port PR81 from ocaml-jst (ocaml-flambda#1024)
131bc12 flambda-backend: Merge ocaml-jst 2022-12-13 (ocaml-flambda#1022)
06c189a flambda-backend: Make stack allocation the default (ocaml-flambda#1013)
98debd5 flambda-backend: Initial support for value slots not of value kind (ocaml-flambda#946)
deb1714 flambda-backend: Add is_last flag to closinfo words (ocaml-flambda#938)
d07fce1 flambda-backend: Disable poll insertion in Configure (ocaml-flambda#967)
0f1ce0e flambda-backend: Regenerate ocaml/configure autoconf 2.69 (instead of 2.71) (ocaml-flambda#1012)
27132d8 flambda-backend: Fix for spurious typing error related to expanding through functor arguments (ocaml-flambda#997)
724fb68 flambda-backend: Use `Compilation_unit.t` instead of `Ident.t` for globals (ocaml-flambda#871)
396d5b8 flambda-backend: Add a test for frametable setup in natdynlinked libraries (ocaml-flambda#983)
b73ab12 flambda-backend: Fix invocation of `caml_shared_startup` in native dynlink (ocaml-flambda#980)
7c7d75a flambda-backend: Fix split_default_wrapper which did not trigger anymore with flambda2 (ocaml-flambda#970)
8fb75bd flambda-backend: Port ocaml/ocaml#11727 and ocaml/ocaml#11732 (ocaml-flambda#965)
fdb7987 flambda-backend: Fix include functor issue after 4.14 merge. (ocaml-flambda#948)
9745cdb flambda-backend: Print -dprofile/-dtimings output to stdout like 4.12 (ocaml-flambda#943)
5f51f21 flambda-backend: Merge pull request ocaml-flambda#932 from mshinwell/4.14-upgrade
841687d flambda-backend: Run make alldepend in ocaml/ (ocaml-flambda#936)
72a7658 flambda-backend: Remove reformatting changes only in dynlink/dune (preserving PR889 and adjusting to minimise diff)
6d758cd flambda-backend: Revert whitespace changes in dune files, to match upstream
c86bf6e flambda-backend: Remove duplicate tests for polling
971dbeb flambda-backend: Testsuite fixes
32f8356 flambda-backend: Topeval fix for symbols patch
befea01 flambda-backend: Compilation fixes / rectify merge faults
a84543f flambda-backend: Merge ocaml-jst
8e65056 flambda-backend: Merge ocaml-jst
4d70045 flambda-backend: Remove filename from system frametable (amd64) (ocaml-flambda#920)
5e57b7d flambda-backend: Bugfix for runtime frame_descr logic for C frames (ocaml-flambda#918)
6423d5e flambda-backend: Merge pull request ocaml-flambda#914 from mshinwell/merge-ocaml-jst-2022-10-24
ead605c flambda-backend: Add a missing Extract_exception (ocaml-flambda#916)
c8f1481 flambda-backend: Resolve conflicts and add specialise/specialised attributes to Builtin_attributes
cf4d0d3 flambda-backend: Merge fixes (#21)
c2f742f flambda-backend: Re-enable some tests for Flambda2 (ocaml-flambda#881)
3d38d13 flambda-backend: Long frames in frametable (ocaml-flambda#797)
85aec7b flambda-backend: Add loop attribute to Builtin_attributes
c0f16e3 flambda-backend: Compilation fixes
90dea23 flambda-backend: Merge flambda-backend/main
5acc6ea flambda-backend: Fixes after merge
e501946 flambda-backend: Merge ocaml-jst
115083b flambda-backend: Merge ocaml-jst
9943b2e flambda-backend: Revert "Revert "Transform tail-recursive functions into recursive continuations (ocaml-flambda#893)"" (ocaml-flambda#909)
ce339f1 flambda-backend: Fix alloc modes and call kinds for overapplications (ocaml-flambda#902)
e6a317c flambda-backend: Revert "Transform tail-recursive functions into recursive continuations (ocaml-flambda#893)"
853c488 flambda-backend: Transform tail-recursive functions into recursive continuations (ocaml-flambda#893)
5a977e4 flambda-backend: Fix missing End_region primitives on switch arms (ocaml-flambda#898)
7fa7f9d flambda-backend: Add missing dependencies to Dune files (ocaml-flambda#889)
3cd36f0 flambda-backend: Have Lambda `Pgetglobal` and `Psetglobal` take `Compilation_unit.t` (ocaml-flambda#896)
7565915 flambda-backend: [@poll error] attribute (ocaml-flambda#745)
9eb9448 flambda-backend: Backport the main safepoints PRs (ocaml-flambda#740)
689bdda flambda-backend: Add strict mode for ocamldep (ocaml-flambda#892)

git-subtree-dir: ocaml
git-subtree-split: b11eea1
@stedolan
Copy link
Contributor

stedolan commented Feb 8, 2023

What is going on here? It sounds from the description that a large proportion of *.cm* is instances of Compilation_unit., otherwise shrinking them wouldn't have much effect. But that can't be right?

@mshinwell
Copy link
Collaborator Author

From what I recall, there are a lot of values of that type in the .cm* files, in particular in the import lists.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
None yet
Projects
None yet
Development

Successfully merging this pull request may close these issues.

3 participants