since `up` and `values` are both pointer-aligned the type field will
also be pointer-aligned, wasting 48 bits of space on most machines. we
can get away with removing the type field altogether by encoding some
information into the `with` expr that created the env to begin with,
reducing the GC load for the absolutely massive amount of single-entry
envs we create for lambdas. this reduces memory usage of system eval by
quite a bit (reducing heap size of our system eval from 8.4GB to 8.23GB)
and gives similar savings in eval time.
running `nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'`
before:
Time (mean ± σ): 5.576 s ± 0.003 s [User: 5.197 s, System: 0.378 s]
Range (min … max): 5.572 s … 5.581 s 10 runs
after:
Time (mean ± σ): 5.408 s ± 0.002 s [User: 5.019 s, System: 0.388 s]
Range (min … max): 5.405 s … 5.411 s 10 runs
There's no good reason to deprecate it:
- For consistency reasons it should continue to exist, such that all
primitive types have a corresponding `builtins.is*` primop.
- There's no implementation cost to continuing to have this function
- It costs users time to try to migrate away from it, e.g.
https://github.com/NixOS/nixpkgs/pull/219747 and https://github.com/NixOS/nixpkgs/pull/275548
- Using it can give easier-to-read code like `all isNull list`
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
this also reduces forceValue code size and removes the need for
hideInDiagnostics. coopting thunk forcing like this has the additional
benefit of clarifying how these errors can happen in the first place.
forceValue is extremely hot. interestingly adding likeliness annotations
to the branches does not seem to make a difference.
before:
Time (mean ± σ): 4.224 s ± 0.005 s [User: 3.711 s, System: 0.512 s]
Range (min … max): 4.218 s … 4.234 s 10 runs
after:
Time (mean ± σ): 4.140 s ± 0.009 s [User: 3.647 s, System: 0.492 s]
Range (min … max): 4.130 s … 4.152 s 10 runs
almost all uses of this are interactive, except for deepSeq. deepSeq is
going to be expensive and rare enough to not care much about, and
Value::determinePos should usually be cheap enough to not be too much of
a burden in any case.
~1% parser speedup from not using TLS indirections, less on system eval.
this could have also gone in flex yyextra data, but that's significantly
slower for some reason (albeit still faster than thread locals).
before:
Time (mean ± σ): 4.231 s ± 0.004 s [User: 3.725 s, System: 0.504 s]
Range (min … max): 4.226 s … 4.240 s 10 runs
after:
Time (mean ± σ): 4.224 s ± 0.005 s [User: 3.711 s, System: 0.512 s]
Range (min … max): 4.218 s … 4.234 s 10 runs
~2% speedup on parsing without eval, less (but still significant) on
system eval. having flex generate faster parsers leads to very strange
misparses. maybe re2c is worth investigating.
before:
Time (mean ± σ): 4.260 s ± 0.003 s [User: 3.754 s, System: 0.505 s]
Range (min … max): 4.257 s … 4.266 s 10 runs
after:
Time (mean ± σ): 4.231 s ± 0.004 s [User: 3.725 s, System: 0.504 s]
Range (min … max): 4.226 s … 4.240 s 10 runs
as written the comparisons generate copies, even though it looks as
though they shouldn't.
before:
Time (mean ± σ): 4.396 s ± 0.002 s [User: 3.894 s, System: 0.501 s]
Range (min … max): 4.393 s … 4.399 s 10 runs
after:
Time (mean ± σ): 4.260 s ± 0.003 s [User: 3.754 s, System: 0.505 s]
Range (min … max): 4.257 s … 4.266 s 10 runs
checking for isBlackhole in the forceValue hot path is rather more
expensive than necessary, and with a little bit of trickery we can move
such handling into the isApp case. small performance benefit, but under
some circumstances we've seen 2% improvement as well.
〉 nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
before:
Time (mean ± σ): 4.429 s ± 0.002 s [User: 3.929 s, System: 0.500 s]
Range (min … max): 4.427 s … 4.433 s 10 runs
after:
Time (mean ± σ): 4.396 s ± 0.002 s [User: 3.894 s, System: 0.501 s]
Range (min … max): 4.393 s … 4.399 s 10 runs
resizing a std::string clears the newly added bytes, which is not
necessary here and comes with a ~1.4% slowdown on our test nixos config.
〉 nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
before:
Time (mean ± σ): 4.486 s ± 0.003 s [User: 3.978 s, System: 0.507 s]
Range (min … max): 4.482 s … 4.492 s 10 runs
after:
Time (mean ± σ): 4.429 s ± 0.002 s [User: 3.929 s, System: 0.500 s]
Range (min … max): 4.427 s … 4.433 s 10 runs
On macOS in the `nix develop` shell, `make
tests/functional/logging.sh.test` errors:
++(logging.sh:18) mktemp
+(logging.sh:18) builder=/var/folders/z5/fclwwdms3r1gq4k4p3pkvvc00000gn/T/tmp.StuabKUhMh
+(logging.sh:19) echo -e '#!/bin/sh\nmkdir $out'
+++(logging.sh:22) mktemp -d
++(logging.sh:22) nix-build -E 'with import ./config.nix; mkDerivation { name = "fnord"; builder = /var/folders/z5/fclwwdms3r1gq4k4p3pkvvc00000gn/T/tmp.StuabKUhMh; }' --out-link /var/folders/z5/fclwwdms3r1gq4k4p3pkvvc00000gn/T/tmp.oaKcy0NXqC/result
error:
… while calling the 'derivationStrict' builtin
at <nix/derivation-internal.nix>:9:12:
8|
9| strict = derivationStrict drvAttrs;
| ^
10|
… while evaluating derivation 'fnord'
whose name attribute is located at «string»:1:42
… while evaluating attribute 'args' of derivation 'fnord'
at /Users/wiggles/nix/tests/functional/config.nix:23:7:
22| builder = shell;
23| args = ["-e" args.builder or (builtins.toFile "builder-${args.name}.sh" ''
| ^
24| if [ -e "$NIX_ATTRS_SH_FILE" ]; then source $NIX_ATTRS_SH_FILE; fi;
error: path '/var' is a symlink
+(logging.sh:22) outp=
++(logging.sh:22) onError
++(/Users/wiggles/nix/tests/functional/common/vars-and-functions.sh:237) set +x
logging.sh: test failed at:
main in logging.sh:22
This is because `mktemp` returns a path like
`/var/folders/z5/fclwwdms3r1gq4k4p3pkvvc00000gn/T/tmp.qDY24l6bIM`,
where `/var` is a symlink to `/private/var`.
Then, we attempt to use that path as a `builder`, which errors because
symlinks are impure or whatever.
Anyways, we can fix this by using `realpath "$(mktemp)"` instead of
`mktemp` directly.
NB: This error doesn't seem to happen when I run the tests through `nix
flake check`. I'm not sure if Nix does something to `TMP` in that case.
`nix flake check` had these warnings:
trace: warning: Module argument `nodes.client.config` is deprecated. Use `nodes.client` instead.
trace: warning: Module argument `nodes.client.config` is deprecated. Use `nodes.client` instead.
trace: warning: The option `services.openssh.permitRootLogin' defined in `/nix/store/3m3hfpmbjdf4w39qfjami7ljhvhczay1-source/tests/nixos/nix-copy.nix' has been renamed to `services.openssh.settings.PermitRootLogin'.
trace: warning: Module argument `nodes.http_dns.config` is deprecated. Use `nodes.http_dns` instead.
trace: warning: Module argument `nodes.github.config` is deprecated. Use `nodes.github` instead.
trace: warning: Module argument `nodes.sourcehut.config` is deprecated. Use `nodes.sourcehut` instead.
It might seem obnoxious to have yet more configure flags, but I found
controlling both the unit and functional tests with one flag was quite
confusing because they are so different:
- unit tests depending on building, functional tests don't (e.g. when
we test already-built Nix)
- unit tests can be installed, functional tests cannot
- unit tests neeed extra libraries (GTest, RapidCheck), functional
tests need extra executables (jq).
- unit tests are run by `make check`, functional tests are run by `make
installcheck`
Really on a technical level, they seem wholly independent. Only on a
human level ("they are both are tests") do they have anything in common.
I had messed up the logic in cross builds because of this. Now I
split the flag in two (and cleaned up a few other inconsistencies), and
the logic fixed itself.
Co-Authored-By: Robert Hensing <roberth@users.noreply.github.com>
* docs: add link to project board to PRs
* Update .github/PULL_REQUEST_TEMPLATE.md
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
* fix wording
* add note on the process
---------
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
