## Summary
This PR consolidates the concurrency limits used throughout `uv` and
exposes two limits, `UV_CONCURRENT_DOWNLOADS` and
`UV_CONCURRENT_BUILDS`, as environment variables.
Currently, `uv` has a number of concurrent streams that it buffers using
relatively arbitrary limits for backpressure. However, many of these
limits are conflated. We run a relatively small number of tasks overall
and should start most things as soon as possible. What we really want to
limit are three separate operations:
- File I/O. This is managed by tokio's blocking pool and we should not
really have to worry about it.
- Network I/O.
- Python build processes.
Because the current limits span a broad range of tasks, it's possible
that a limit meant for network I/O is occupied by tasks performing
builds, reading from the file system, or even waiting on a `OnceMap`. We
also don't limit build processes that end up being required to perform a
download. While this may not pose a performance problem because our
limits are relatively high, it does mean that the limits do not do what
we want, making it tricky to expose them to users
(https://github.com/astral-sh/uv/issues/1205,
https://github.com/astral-sh/uv/issues/3311).
After this change, the limits on network I/O and build processes are
centralized and managed by semaphores. All other tasks are unbuffered
(note that these tasks are still bounded, so backpressure should not be
a problem).
Scott schafer got me the idea: We can avoid repeating the path for
workspaces dependencies everywhere if we declare them in the virtual
package once and treat them as workspace dependencies from there on.
First, replace all usages in files in-place. I used my editor for this.
If someone wants to add a one-liner that'd be fun.
Then, update directory and file names:
```
# Run twice for nested directories
find . -type d -print0 | xargs -0 rename s/puffin/uv/g
find . -type d -print0 | xargs -0 rename s/puffin/uv/g
# Update files
find . -type f -print0 | xargs -0 rename s/puffin/uv/g
```
Then add all the files again
```
# Add all the files again
git add crates
git add python/uv
# This one needs a force-add
git add -f crates/uv-trampoline
```
This PR tweaks the representation of `Tags` in order to offer a
faster implementation of `WheelFilename::is_compatible`. We now use a
nested map of tags that lets us avoid looping over every supported
platform tag. As the code comments suggest, that is the essential gain.
We still do not mind looping over the tags in each wheel name since they
tend to be quite small. And pushing our thumb on that side of things can
make things worse overall since it would likely slow down WheelFilename
construction itself.
For micro-benchmarks, we improve considerably for compatibility
checking:
$ critcmp base test3
group base test3
----- ---- -----
build_platform_tags/burntsushi-archlinux 1.00 46.2±0.28µs ? ?/sec 2.48
114.8±0.45µs ? ?/sec
wheelname_parsing/flyte-long-compatible 1.00 624.8±3.31ns 174.0 MB/sec
1.01 629.4±4.30ns 172.7 MB/sec
wheelname_parsing/flyte-long-incompatible 1.00 743.6±4.23ns 165.4 MB/sec
1.00 746.9±4.62ns 164.7 MB/sec
wheelname_parsing/flyte-short-compatible 1.00 526.7±4.76ns 54.3 MB/sec
1.01 530.2±5.81ns 54.0 MB/sec
wheelname_parsing/flyte-short-incompatible 1.00 540.4±4.93ns 60.0 MB/sec
1.01 545.7±5.31ns 59.4 MB/sec
wheelname_parsing_failure/flyte-long-extension 1.00 13.6±0.13ns 3.2
GB/sec 1.01 13.7±0.14ns 3.2 GB/sec
wheelname_parsing_failure/flyte-short-extension 1.00 14.0±0.20ns 1160.4
MB/sec 1.01 14.1±0.14ns 1146.5 MB/sec
wheelname_tag_compatibility/flyte-long-compatible 11.33 159.8±2.79ns
680.5 MB/sec 1.00 14.1±0.23ns 7.5 GB/sec
wheelname_tag_compatibility/flyte-long-incompatible 237.60
1671.8±37.99ns 73.6 MB/sec 1.00 7.0±0.08ns 17.1 GB/sec
wheelname_tag_compatibility/flyte-short-compatible 16.07 223.5±8.60ns
128.0 MB/sec 1.00 13.9±0.30ns 2.0 GB/sec
wheelname_tag_compatibility/flyte-short-incompatible 149.83 628.3±2.13ns
51.6 MB/sec 1.00 4.2±0.10ns 7.6 GB/sec
We do regress slightly on the time it takes for `Tags::new` to run, but
this is somewhat expected. And in absolute terms, 114us is perfectly
acceptable given that it's only executed ~once for each `puffin`
invocation.
Ad hoc benchmarks indicate an overall 25% perf improvement in `puffin
pip-compile` times. This roughly corresponds with how much time
`is_compatible` was taking. Indeed, profiling confirms that it has
virtually disappeared from the profile.
Fixes#157
Ibraheem Ahmed