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Previously, Nix strings were represented as a Box (within Value)
pointing to a tuple of an optional context, and another Box pointing to
the actual string allocation itself. This is pretty inefficient, both in
terms of memory usage (we use 48 whole bytes for a None context!) and in
terms of the extra indirection required to get at the actual data. It
was necessary, however, because with native Rust DSTs if we had
something like `struct NixString(Option<NixContext>, BStr)` we could
only pass around *fat* pointers to that value (with the length in the
pointer) and that'd make Value need to be bigger (which is a waste of
both memory and cache space, since that memory would be unused for all
other Values).
Instead, this commit implements *manual* allocation of a packed string
representation, with the length *in the allocation* as a field past the
context. This requires a big old pile of unsafe Rust, but the payoff is
clear:
hello outpath time: [882.18 ms 897.16 ms 911.23 ms]
change: [-15.143% -13.819% -12.500%] (p = 0.00 < 0.05)
Performance has improved.
Fortunately this change can be localized entirely within
value/string.rs, since we were abstracting things out nicely.
Change-Id: Ibf56dd16c9c503884f64facbb7f0ac596463efb6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10852
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Autosubmit: aspen <root@gws.fyi>
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This reverts commit d9565a4d0af3bffd735a77aa6f1fd0ec0e03b14a.
Reason for revert: this was intentional - putting Rc::clone instead of
.clone is a common Rust idiom, and makes it explicit that we're cloning
a shared reference, not an underlying resource
Change-Id: I41a5f323ee35d7025dc7bb02f7d5d05d0051798d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10995
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
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We add a new set of builtins called `import_builtins`, which
will contain import-related builtins, such as `builtins.path` and
`builtins.filterSource`. Both can import paths into the store, with
various knobs to alter the result, e.g. filtering, renaming, expected
hashes.
We introduce `filtered_ingest` which will drive the filtered ingestion
via the Nix function via the generator machinery, and then we register
the root node to the path info service inside the store.
`builtins.filterSource` is very simple, `builtins.path` is a more
complicated model requiring the same logic albeit more sophisticated
with name customization, file ingestion method and expected SHA-256.
Change-Id: I1083f37808b35f7b37818c8ffb9543d9682b2de2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10654
Autosubmit: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
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