This was lost after 2.32 while making the accessor lazy. We can restore the support
for it pretty easily. Also this is significant optimization for nix nar cat.
E.g. with a NAR of a linux repo this speeds up by ~3x:
Benchmark 1: nix nar cat /tmp/linux.nar README
Time (mean ± σ): 737.2 ms ± 5.6 ms [User: 298.1 ms, System: 435.7 ms]
Range (min … max): 728.6 ms … 746.9 ms 10 runs
Benchmark 2: build/src/nix/nix nar cat /tmp/linux.nar README
Time (mean ± σ): 253.5 ms ± 2.9 ms [User: 56.4 ms, System: 196.3 ms]
Range (min … max): 248.1 ms … 258.7 ms 12 runs
The whole NarAccessor -> listing -> lazy NarAccessor is very weird. Source
can now be seek-ed over when supported, so we can support it pretty easily.
Alternatively we could also make it single-pass very easily with a custom
FileSystemObjectSink. It will get removed in a follow-up commit anyway.
This somehow fails https://hydra.nixos.org/build/315675349/nixlog/1. I don't know the exact
details, but it seems that something goes very wrong with LTO and sanitizers that lead to the
string literal to be moved? Instead of relying on the string literal deduplication to provide
a consistent address we can use a global. That should have a single address (modulo wonky copy
relocations).
I didn't do things quite right in 496e43ec72:
- Forgot to remove the now-redundant `isAllowed` check.
- Called the non-virtual, not the superclass's impl, in
`addDependencyPrep`, causing bad recursion / UB.
Doing this fixes a crash I encountered with manual testing an Nix Ninja
--- hopefully we will get Nix Ninja or similar in a NixOS test longer
term to defend against this thing happening again.
We have the machinery to make a more informative error, telling the
user what format was actually encountered, and not just that it is not
the format that was requested.
The S3BinaryCacheStoreConfig::doc() function was returning a minimal
hardcoded 3-line string instead of including the comprehensive
documentation from s3-binary-cache-store.md.
This was introduced in PR #13752 which moved the prose documentation to
the markdown file but forgot to update the doc() function to use it.
The previous commit hacked it into the output of `nix path-info --json`,
this cleans that up my making it an actual field of that data type, and
part of the canonical JSON serializers for it (and `ValidPathInfo` and
`NarInfo`).
Beyond cleaning up the JSON code, this also opens the doors to things
like:
- Binary caches that contain store objects that don't all belong in the
same store directory
- Relocatable store objects which carefully don't mention any store
directory by absolute path, and instead use relative paths for
anything. (#9549)
As discussed today at great length in the Nix meeting, we don't want to
break the format, but we also don't want to impede the improvement of
JSON formats. The solution is to add a new flag for control the output
format.
Note that prior to the release, we may want to replace `--json
--json-format N` with `--json=N`, but this is being left for a separate
PR, as we don't yet have `=` support for CLI flags.
Fix#14532.
As discussed on the call today:
1. We'll stick with `format = "base16"` and `hash = "<hash>"`, not do
`base16 = "<hash>"`, in order to be forward compatible with
supporting more versioning formats.
The motivation we discussed for someday *possibly* doing this is
making it easier to write very slap-dash lang2nix tools that create
(not consume) derivations with dynamic derivations.
2. We will remove support for non-base16 (and make that the default, not
base64) in `Hash`, so this is strictly forward contingency, *not*
yet something we support. (And also not something we have concrete
plans to start supporting.)
This leads to incredibly wasteful refreshes (see [^]) when oids are not found.
Since we are writing the pack files only once per unpacking we should not bother
with this refreshing at all.
This brings down the number of syscalls during `nix flake metadata "https://releases.nixos.org/nixos/25.05/nixos-25.05.813095.1c8ba8d3f763/nixexprs.tar.xz" --store "dummy://?read-only=false"`
Down from 576334 to just 6235 (100x less syscalls):
(Before)
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ------------------
32.98 0.625288 3 162898 getdents64
29.58 0.560686 3 163514 81917 openat
15.01 0.284509 3 81819 186 newfstatat
10.99 0.208349 2 81601 close
10.56 0.200145 2 81552 fstat
All these are coming from [2] and are totally useless.
(After)
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ------------------
76.47 0.108558 247 438 20 futex
6.55 0.009292 18 513 munmap
3.30 0.004680 7 639 492 openat
2.68 0.003803 10 359 write
2.30 0.003268 2 1146 read
2.26 0.003215 3 870 mmap
[^]: 58d9363f02/include/git2/sys/odb_backend.h (L68-L75)
[2]: 58d9363f02/src/libgit2/odb_pack.c (L517-L546)
The interrupting code is no longer relevant. Since
054be50257 logging no longer checks for interrupts
and in general logging should be noexcept.
Co-authored-by: Alois Wohlschlager <alois1@gmx-topmail.de>
Cherry-picked-from: https://gerrit.lix.systems/c/lix/+/1097
