we'll retain the old coerceToString interface that returns a string, but callers
that don't need the returned value to outlive the Value it came from can save
copies by using the new interface instead. for values that weren't stringy we'll
pass a new buffer argument that'll be used for storage and shouldn't be
inspected.
It’s totally valid to have entries in `NIX_PATH` that aren’t valid paths
(they can even be arbitrary urls or `channel:<channel-name>`).
Fix#5998 and #5980
keeping it as a simple data member means it won't be scanned by the GC, so
eventually the GC will collect a cache that is still referenced (resulting in
use-after-free of cache elements).
fixes#5962
- Make passing the position to `forceValue` mandatory,
this way we remember people that the position is
important for better error messages
- Add pos to all `forceValue` calls
This no longer worked correctly because 'path' is uninitialised when
an exception occurs, leading to errors like
… while importing ''
at /nix/store/rrzz5b1pshvzh1437ac9nkl06br81lkv-source/flake.nix:352:13:
So move the adding of the error context into realisePath().
if we defer the duplicate argument check for lambda formals we can use more
efficient data structures for the formals set, and we can get rid of the
duplication of formals names to boot. instead of a list of formals we've seen
and a set of names we'll keep a vector instead and run a sort+dupcheck step
before moving the parsed formals into a newly created lambda. this improves
performance on search and rebuild by ~1%, pure parsing gains more (about 4%).
this does reorder lambda arguments in the xml output, but the output is still
stable. this shouldn't be a problem since argument order is not semantically
important anyway.
before
nix search --no-eval-cache --offline ../nixpkgs hello
Time (mean ± σ): 8.550 s ± 0.060 s [User: 6.470 s, System: 1.664 s]
Range (min … max): 8.435 s … 8.666 s 20 runs
nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 346.7 ms ± 2.1 ms [User: 312.4 ms, System: 34.2 ms]
Range (min … max): 343.8 ms … 353.4 ms 20 runs
nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.720 s ± 0.031 s [User: 2.415 s, System: 0.231 s]
Range (min … max): 2.662 s … 2.780 s 20 runs
after
nix search --no-eval-cache --offline ../nixpkgs hello
Time (mean ± σ): 8.462 s ± 0.063 s [User: 6.398 s, System: 1.661 s]
Range (min … max): 8.339 s … 8.542 s 20 runs
nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 329.1 ms ± 1.4 ms [User: 296.8 ms, System: 32.3 ms]
Range (min … max): 326.1 ms … 330.8 ms 20 runs
nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.687 s ± 0.035 s [User: 2.392 s, System: 0.228 s]
Range (min … max): 2.626 s … 2.754 s 20 runs
string expressions by and large do not need the benefits a Symbol gives us,
instead they pollute the symbol table and cause unnecessary overhead for almost
all strings. the one place we can think of that benefits from them (attrpaths
with expressions) extracts the benefit in the parser, which we'll have to touch
anyway when changing ExprString to hold strings.
this gives a sizeable improvement on of 3-5% on all benchmarks we've run.
before
nix search --no-eval-cache --offline ../nixpkgs hello
Time (mean ± σ): 8.844 s ± 0.045 s [User: 6.750 s, System: 1.663 s]
Range (min … max): 8.758 s … 8.922 s 20 runs
nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 367.4 ms ± 3.3 ms [User: 332.3 ms, System: 35.2 ms]
Range (min … max): 364.0 ms … 375.2 ms 20 runs
nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.810 s ± 0.030 s [User: 2.517 s, System: 0.225 s]
Range (min … max): 2.742 s … 2.854 s 20 runs
after
nix search --no-eval-cache --offline ../nixpkgs hello
Time (mean ± σ): 8.533 s ± 0.068 s [User: 6.485 s, System: 1.642 s]
Range (min … max): 8.404 s … 8.657 s 20 runs
nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 347.6 ms ± 3.1 ms [User: 313.1 ms, System: 34.5 ms]
Range (min … max): 343.3 ms … 354.6 ms 20 runs
nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.709 s ± 0.032 s [User: 2.414 s, System: 0.232 s]
Range (min … max): 2.655 s … 2.788 s 20 runs
it can be replaced with StringToken if we add another bit if information to
StringToken, namely whether this string should take part in indentation scanning
or not. since all escaping terminates indentation scanning we need to set this
bit only for the non-escaped IND_STRING rule.
this improves performance by about 1%.
before
nix search --no-eval-cache --offline ../nixpkgs hello
Time (mean ± σ): 8.880 s ± 0.048 s [User: 6.809 s, System: 1.643 s]
Range (min … max): 8.781 s … 8.993 s 20 runs
nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 375.0 ms ± 2.2 ms [User: 339.8 ms, System: 35.2 ms]
Range (min … max): 371.5 ms … 379.3 ms 20 runs
nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.831 s ± 0.040 s [User: 2.536 s, System: 0.225 s]
Range (min … max): 2.769 s … 2.912 s 20 runs
after
nix search --no-eval-cache --offline ../nixpkgs hello
Time (mean ± σ): 8.832 s ± 0.048 s [User: 6.757 s, System: 1.657 s]
Range (min … max): 8.743 s … 8.921 s 20 runs
nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 367.4 ms ± 3.2 ms [User: 332.7 ms, System: 34.7 ms]
Range (min … max): 364.6 ms … 374.6 ms 20 runs
nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.810 s ± 0.030 s [User: 2.517 s, System: 0.225 s]
Range (min … max): 2.742 s … 2.854 s 20 runs
gives about 1% improvement on system eval, a bit less on nix search.
# before
nix search --no-eval-cache --offline ../nixpkgs hello
Time (mean ± σ): 7.419 s ± 0.045 s [User: 6.362 s, System: 0.794 s]
Range (min … max): 7.335 s … 7.517 s 20 runs
nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.921 s ± 0.023 s [User: 2.626 s, System: 0.210 s]
Range (min … max): 2.883 s … 2.957 s 20 runs
# after
nix search --no-eval-cache --offline ../nixpkgs hello
Time (mean ± σ): 7.370 s ± 0.059 s [User: 6.333 s, System: 0.791 s]
Range (min … max): 7.286 s … 7.541 s 20 runs
nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.891 s ± 0.033 s [User: 2.606 s, System: 0.210 s]
Range (min … max): 2.823 s … 2.958 s 20 runs
mainly to avoid an allocation and a copy of a string that can be
modified in place (ever since EvalState holds on to the buffer, not the
generated parser itself).
# before
Benchmark 1: nix search --offline nixpkgs hello
Time (mean ± σ): 571.7 ms ± 2.4 ms [User: 563.3 ms, System: 8.0 ms]
Range (min … max): 566.7 ms … 579.7 ms 50 runs
Benchmark 2: nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 376.6 ms ± 1.0 ms [User: 345.8 ms, System: 30.5 ms]
Range (min … max): 374.5 ms … 379.1 ms 50 runs
Benchmark 3: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.922 s ± 0.006 s [User: 2.707 s, System: 0.215 s]
Range (min … max): 2.906 s … 2.934 s 50 runs
# after
Benchmark 1: nix search --offline nixpkgs hello
Time (mean ± σ): 570.4 ms ± 2.8 ms [User: 561.3 ms, System: 8.6 ms]
Range (min … max): 564.6 ms … 578.1 ms 50 runs
Benchmark 2: nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 375.4 ms ± 1.3 ms [User: 343.2 ms, System: 31.7 ms]
Range (min … max): 373.4 ms … 378.2 ms 50 runs
Benchmark 3: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.925 s ± 0.006 s [User: 2.704 s, System: 0.219 s]
Range (min … max): 2.910 s … 2.942 s 50 runs
when given a string yacc will copy the entire input to a newly allocated
location so that it can add a second terminating NUL byte. since the
parser is a very internal thing to EvalState we can ensure that having
two terminating NUL bytes is always possible without copying, and have
the parser itself merely check that the expected NULs are present.
# before
Benchmark 1: nix search --offline nixpkgs hello
Time (mean ± σ): 572.4 ms ± 2.3 ms [User: 563.4 ms, System: 8.6 ms]
Range (min … max): 566.9 ms … 579.1 ms 50 runs
Benchmark 2: nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 381.7 ms ± 1.0 ms [User: 348.3 ms, System: 33.1 ms]
Range (min … max): 380.2 ms … 387.7 ms 50 runs
Benchmark 3: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.936 s ± 0.005 s [User: 2.715 s, System: 0.221 s]
Range (min … max): 2.923 s … 2.946 s 50 runs
# after
Benchmark 1: nix search --offline nixpkgs hello
Time (mean ± σ): 571.7 ms ± 2.4 ms [User: 563.3 ms, System: 8.0 ms]
Range (min … max): 566.7 ms … 579.7 ms 50 runs
Benchmark 2: nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 376.6 ms ± 1.0 ms [User: 345.8 ms, System: 30.5 ms]
Range (min … max): 374.5 ms … 379.1 ms 50 runs
Benchmark 3: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.922 s ± 0.006 s [User: 2.707 s, System: 0.215 s]
Range (min … max): 2.906 s … 2.934 s 50 runs
speeds up parsing by ~3%, system builds by a bit more than 1%
# before
Benchmark 1: nix search --offline nixpkgs hello
Time (mean ± σ): 574.7 ms ± 2.8 ms [User: 566.3 ms, System: 8.0 ms]
Range (min … max): 569.2 ms … 580.7 ms 50 runs
Benchmark 2: nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 394.4 ms ± 0.8 ms [User: 361.8 ms, System: 32.3 ms]
Range (min … max): 392.7 ms … 395.7 ms 50 runs
Benchmark 3: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.976 s ± 0.005 s [User: 2.757 s, System: 0.218 s]
Range (min … max): 2.966 s … 2.990 s 50 runs
# after
Benchmark 1: nix search --offline nixpkgs hello
Time (mean ± σ): 572.4 ms ± 2.3 ms [User: 563.4 ms, System: 8.6 ms]
Range (min … max): 566.9 ms … 579.1 ms 50 runs
Benchmark 2: nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 381.7 ms ± 1.0 ms [User: 348.3 ms, System: 33.1 ms]
Range (min … max): 380.2 ms … 387.7 ms 50 runs
Benchmark 3: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.936 s ± 0.005 s [User: 2.715 s, System: 0.221 s]
Range (min … max): 2.923 s … 2.946 s 50 runs
every stringy token the lexer returns is turned into a Symbol and not
used further, so we don't have to strdup. using a string_view is
sufficient, but due to limitations of the current parser we have to use
a POD type that holds the same information.
gives ~2% on system build, 6% on search, 8% on parsing alone
# before
Benchmark 1: nix search --offline nixpkgs hello
Time (mean ± σ): 610.6 ms ± 2.4 ms [User: 602.5 ms, System: 7.8 ms]
Range (min … max): 606.6 ms … 617.3 ms 50 runs
Benchmark 2: nix eval -f hackage-packages.nix
Time (mean ± σ): 430.1 ms ± 1.4 ms [User: 393.1 ms, System: 36.7 ms]
Range (min … max): 428.2 ms … 434.2 ms 50 runs
Benchmark 3: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 3.032 s ± 0.005 s [User: 2.808 s, System: 0.223 s]
Range (min … max): 3.023 s … 3.041 s 50 runs
# after
Benchmark 1: nix search --offline nixpkgs hello
Time (mean ± σ): 574.7 ms ± 2.8 ms [User: 566.3 ms, System: 8.0 ms]
Range (min … max): 569.2 ms … 580.7 ms 50 runs
Benchmark 2: nix eval -f hackage-packages.nix
Time (mean ± σ): 394.4 ms ± 0.8 ms [User: 361.8 ms, System: 32.3 ms]
Range (min … max): 392.7 ms … 395.7 ms 50 runs
Benchmark 3: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.976 s ± 0.005 s [User: 2.757 s, System: 0.218 s]
Range (min … max): 2.966 s … 2.990 s 50 runs
there's a few symbols in primops we can create once and pick them out of
EvalState afterwards instead of creating them every time we need them. this
gives almost 1% speedup to an uncached nix search.
constructing an ostringstream for non-string concats (like integer addition) is
a small constant cost that we can avoid. for string concats we can keep all the
string temporaries we get from coerceToString and concatenate them in one go,
which saves a lot of intermediate temporaries and copies in ostringstream. we
can also avoid copying the concatenated string again by directly allocating it
in GC memory and moving ownership of the concatenated string into the target
value.
saves about 2% on system eval.
before:
Benchmark 1: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.837 s ± 0.031 s [User: 2.562 s, System: 0.191 s]
Range (min … max): 2.796 s … 2.892 s 20 runs
after:
Benchmark 1: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.790 s ± 0.035 s [User: 2.532 s, System: 0.187 s]
Range (min … max): 2.722 s … 2.836 s 20 runs
