Add more profiling traces

Someone suggested I look at
[zed](https://github.com/zed-industries/zed).
It has some interesting performance characteristics compared to projects
I looked at before:
- A lot of workspace members
- git dependencies
- patches

This adds traces that help provide more context for those scenarios when
looking at them.

Some of these areas might be of interest for
optimizing:
- On every invocation, we do a git2 `copy_to` call for each git checkout
- On every invocation, we do a `du` on each git checkout
- It'd be great to avoid parsing every manifest in a git checkout but we
  need to do a full parse to make sure we find all packages (see
  https://rust-lang.zulipchat.com/#narrow/stream/246057-t-cargo/topic/Redundant.20code.20in.20.60GitSouce.60.3F)
- Its suspicious how much time we spend in the "poison" step of
  resolving when its a no-op

Author: epage

src/cargo/core/global_cache_tracker.rs

@@ -1799,6 +1799,7 @@ pub fn is_silent_error(e: &anyhow::Error) -> bool {
 }
 
 /// Returns the disk usage for a git checkout directory.
+#[tracing::instrument]
 pub fn du_git_checkout(path: &Path) -> CargoResult<u64> {
     // !.git is used because clones typically use hardlinks for the git
     // contents. TODO: Verify behavior on Windows.

src/cargo/core/registry.rs

@@ -336,6 +336,7 @@ impl<'gctx> PackageRegistry<'gctx> {
     /// The return value is a `Vec` of patches that should *not* be locked.
     /// This happens when the patch is locked, but the patch has been updated
     /// so the locked value is no longer correct.
+    #[tracing::instrument(skip(self, patch_deps))]
     pub fn patch(
         &mut self,
         url: &Url,
@@ -784,6 +785,7 @@ impl<'gctx> Registry for PackageRegistry<'gctx> {
         }
     }
 
+    #[tracing::instrument(skip_all)]
     fn block_until_ready(&mut self) -> CargoResult<()> {
         if cfg!(debug_assertions) {
             // Force borrow to catch invalid borrows, regardless of which source is used and how it

src/cargo/core/workspace.rs

@@ -723,6 +723,7 @@ impl<'gctx> Workspace<'gctx> {
     /// verifies that those are all valid packages to point to. Otherwise, this
     /// will transitively follow all `path` dependencies looking for members of
     /// the workspace.
+    #[tracing::instrument(skip_all)]
     fn find_members(&mut self) -> CargoResult<()> {
         let Some(workspace_config) = self.load_workspace_config()? else {
             debug!("find_members - only me as a member");
@@ -886,6 +887,7 @@ impl<'gctx> Workspace<'gctx> {
     /// 1. A workspace only has one root.
     /// 2. All workspace members agree on this one root as the root.
     /// 3. The current crate is a member of this workspace.
+    #[tracing::instrument(skip_all)]
     fn validate(&mut self) -> CargoResult<()> {
         // The rest of the checks require a VirtualManifest or multiple members.
         if self.root_manifest.is_none() {
@@ -954,6 +956,7 @@ impl<'gctx> Workspace<'gctx> {
         }
     }
 
+    #[tracing::instrument(skip_all)]
     fn validate_members(&mut self) -> CargoResult<()> {
         for member in self.members.clone() {
             let root = self.find_root(&member)?;
@@ -1812,6 +1815,7 @@ impl WorkspaceRootConfig {
         self.members.is_some()
     }
 
+    #[tracing::instrument(skip_all)]
     fn members_paths(&self, globs: &[String]) -> CargoResult<Vec<PathBuf>> {
         let mut expanded_list = Vec::new();
 

src/cargo/ops/cargo_read_manifest.rs

@@ -34,6 +34,7 @@ pub fn read_package(
     Ok(Package::new(manifest, path))
 }
 
+#[tracing::instrument(skip(source_id, gctx))]
 pub fn read_packages(
     path: &Path,
     source_id: SourceId,

src/cargo/ops/resolve.rs

@@ -386,6 +386,8 @@ pub fn resolve_with_previous<'gctx>(
         register_previous_locks(ws, registry, r, &keep, dev_deps);
 
         // Prefer to use anything in the previous lock file, aka we want to have conservative updates.
+        let span = tracing::span!(tracing::Level::TRACE, "prefer_package_id");
+        let _enter = span.enter();
         for id in r.iter().filter(keep) {
             debug!("attempting to prefer {}", id);
             version_prefs.prefer_package_id(id);
@@ -396,20 +398,23 @@ pub fn resolve_with_previous<'gctx>(
         registry.lock_patches();
     }
 
-    let summaries: Vec<(Summary, ResolveOpts)> = ws
-        .members_with_features(specs, cli_features)?
-        .into_iter()
-        .map(|(member, features)| {
-            let summary = registry.lock(member.summary().clone());
-            (
-                summary,
-                ResolveOpts {
-                    dev_deps,
-                    features: RequestedFeatures::CliFeatures(features),
-                },
-            )
-        })
-        .collect();
+    let summaries: Vec<(Summary, ResolveOpts)> = {
+        let span = tracing::span!(tracing::Level::TRACE, "registry.lock");
+        let _enter = span.enter();
+        ws.members_with_features(specs, cli_features)?
+            .into_iter()
+            .map(|(member, features)| {
+                let summary = registry.lock(member.summary().clone());
+                (
+                    summary,
+                    ResolveOpts {
+                        dev_deps,
+                        features: RequestedFeatures::CliFeatures(features),
+                    },
+                )
+            })
+            .collect()
+    };
 
     let replace = lock_replacements(ws, previous, &keep);
 
@@ -497,6 +502,7 @@ pub fn get_resolved_packages<'gctx>(
 ///
 /// Note that this function, at the time of this writing, is basically the
 /// entire fix for issue #4127.
+#[tracing::instrument(skip_all)]
 fn register_previous_locks(
     ws: &Workspace<'_>,
     registry: &mut PackageRegistry<'_>,
@@ -577,60 +583,64 @@ fn register_previous_locks(
     // crates from crates.io* are not locked (aka added to `avoid_locking`).
     // For dependencies like `log` their previous version in the lock file will
     // come up first before newer version, if newer version are available.
-    let mut path_deps = ws.members().cloned().collect::<Vec<_>>();
-    let mut visited = HashSet::new();
-    while let Some(member) = path_deps.pop() {
-        if !visited.insert(member.package_id()) {
-            continue;
-        }
-        let is_ws_member = ws.is_member(&member);
-        for dep in member.dependencies() {
-            // If this dependency didn't match anything special then we may want
-            // to poison the source as it may have been added. If this path
-            // dependencies is **not** a workspace member, however, and it's an
-            // optional/non-transitive dependency then it won't be necessarily
-            // be in our lock file. If this shows up then we avoid poisoning
-            // this source as otherwise we'd repeatedly update the registry.
-            //
-            // TODO: this breaks adding an optional dependency in a
-            // non-workspace member and then simultaneously editing the
-            // dependency on that crate to enable the feature. For now,
-            // this bug is better than the always-updating registry though.
-            if !is_ws_member && (dep.is_optional() || !dep.is_transitive()) {
+    {
+        let span = tracing::span!(tracing::Level::TRACE, "poison");
+        let _enter = span.enter();
+        let mut path_deps = ws.members().cloned().collect::<Vec<_>>();
+        let mut visited = HashSet::new();
+        while let Some(member) = path_deps.pop() {
+            if !visited.insert(member.package_id()) {
                 continue;
             }
+            let is_ws_member = ws.is_member(&member);
+            for dep in member.dependencies() {
+                // If this dependency didn't match anything special then we may want
+                // to poison the source as it may have been added. If this path
+                // dependencies is **not** a workspace member, however, and it's an
+                // optional/non-transitive dependency then it won't be necessarily
+                // be in our lock file. If this shows up then we avoid poisoning
+                // this source as otherwise we'd repeatedly update the registry.
+                //
+                // TODO: this breaks adding an optional dependency in a
+                // non-workspace member and then simultaneously editing the
+                // dependency on that crate to enable the feature. For now,
+                // this bug is better than the always-updating registry though.
+                if !is_ws_member && (dep.is_optional() || !dep.is_transitive()) {
+                    continue;
+                }
 
-            // If dev-dependencies aren't being resolved, skip them.
-            if !dep.is_transitive() && !dev_deps {
-                continue;
-            }
+                // If dev-dependencies aren't being resolved, skip them.
+                if !dep.is_transitive() && !dev_deps {
+                    continue;
+                }
 
-            // If this is a path dependency, then try to push it onto our
-            // worklist.
-            if let Some(pkg) = path_pkg(dep.source_id()) {
-                path_deps.push(pkg);
-                continue;
-            }
+                // If this is a path dependency, then try to push it onto our
+                // worklist.
+                if let Some(pkg) = path_pkg(dep.source_id()) {
+                    path_deps.push(pkg);
+                    continue;
+                }
 
-            // If we match *anything* in the dependency graph then we consider
-            // ourselves all ok, and assume that we'll resolve to that.
-            if resolve.iter().any(|id| dep.matches_ignoring_source(id)) {
-                continue;
-            }
+                // If we match *anything* in the dependency graph then we consider
+                // ourselves all ok, and assume that we'll resolve to that.
+                if resolve.iter().any(|id| dep.matches_ignoring_source(id)) {
+                    continue;
+                }
 
-            // Ok if nothing matches, then we poison the source of these
-            // dependencies and the previous lock file.
-            debug!(
-                "poisoning {} because {} looks like it changed {}",
-                dep.source_id(),
-                member.package_id(),
-                dep.package_name()
-            );
-            for id in resolve
-                .iter()
-                .filter(|id| id.source_id() == dep.source_id())
-            {
-                add_deps(resolve, id, &mut avoid_locking);
+                // Ok if nothing matches, then we poison the source of these
+                // dependencies and the previous lock file.
+                debug!(
+                    "poisoning {} because {} looks like it changed {}",
+                    dep.source_id(),
+                    member.package_id(),
+                    dep.package_name()
+                );
+                for id in resolve
+                    .iter()
+                    .filter(|id| id.source_id() == dep.source_id())
+                {
+                    add_deps(resolve, id, &mut avoid_locking);
+                }
             }
         }
     }
@@ -660,28 +670,32 @@ fn register_previous_locks(
     let keep = |id: &PackageId| keep(id) && !avoid_locking.contains(id);
 
     registry.clear_lock();
-    for node in resolve.iter().filter(keep) {
-        let deps = resolve
-            .deps_not_replaced(node)
-            .map(|p| p.0)
-            .filter(keep)
-            .collect::<Vec<_>>();
-
-        // In the v2 lockfile format and prior the `branch=master` dependency
-        // directive was serialized the same way as the no-branch-listed
-        // directive. Nowadays in Cargo, however, these two directives are
-        // considered distinct and are no longer represented the same way. To
-        // maintain compatibility with older lock files we register locked nodes
-        // for *both* the master branch and the default branch.
-        //
-        // Note that this is only applicable for loading older resolves now at
-        // this point. All new lock files are encoded as v3-or-later, so this is
-        // just compat for loading an old lock file successfully.
-        if let Some(node) = master_branch_git_source(node, resolve) {
-            registry.register_lock(node, deps.clone());
-        }
+    {
+        let span = tracing::span!(tracing::Level::TRACE, "register_lock");
+        let _enter = span.enter();
+        for node in resolve.iter().filter(keep) {
+            let deps = resolve
+                .deps_not_replaced(node)
+                .map(|p| p.0)
+                .filter(keep)
+                .collect::<Vec<_>>();
+
+            // In the v2 lockfile format and prior the `branch=master` dependency
+            // directive was serialized the same way as the no-branch-listed
+            // directive. Nowadays in Cargo, however, these two directives are
+            // considered distinct and are no longer represented the same way. To
+            // maintain compatibility with older lock files we register locked nodes
+            // for *both* the master branch and the default branch.
+            //
+            // Note that this is only applicable for loading older resolves now at
+            // this point. All new lock files are encoded as v3-or-later, so this is
+            // just compat for loading an old lock file successfully.
+            if let Some(node) = master_branch_git_source(node, resolve) {
+                registry.register_lock(node, deps.clone());
+            }
 
-        registry.register_lock(node, deps);
+            registry.register_lock(node, deps);
+        }
     }
 
     /// Recursively add `node` and all its transitive dependencies to `set`.

src/cargo/sources/git/utils.rs

@@ -164,6 +164,7 @@ impl GitRemote {
 
 impl GitDatabase {
     /// Checkouts to a revision at `dest`ination from this database.
+    #[tracing::instrument(skip(self, gctx))]
     pub fn copy_to(
         &self,
         rev: git2::Oid,