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Performance optimizations #314

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20af1c8
sdk/rust: Skip ensure_parent_dirs when parent is already in delta layer
penberg Feb 3, 2026
29cd8b7
sdk/rust: Skip base lookup for pure delta directories
penberg Feb 3, 2026
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66 changes: 50 additions & 16 deletions sdk/rust/src/filesystem/overlayfs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -626,7 +626,18 @@ impl FileSystem for OverlayFS {
return Ok(Some(stats));
}

// Try base
// If the parent is a "pure delta" directory (created in delta, not copied from base),
// there's no point checking the base layer - children can't exist there. This avoids
// unnecessary stat() syscalls when looking up entries in directories like node_modules/
// that were created entirely within the delta layer.
if let Some(delta_parent) = delta_parent_ino {
if self.get_origin_ino(delta_parent).is_none() {
// Parent exists in delta with no base origin - it's a pure delta directory
return Ok(None);
}
}

// Try base - parent either exists in base or was copied from base
let base_parent_ino = if parent_info.layer == Layer::Base {
parent_info.underlying_ino
} else {
Expand Down Expand Up @@ -909,14 +920,18 @@ impl FileSystem for OverlayFS {
// Remove whiteout if exists
self.remove_whiteout(&path).await?;

// Ensure parent dirs exist in delta
self.ensure_parent_dirs(&path, uid, gid).await?;

// Get delta parent inode
// Resolve the delta parent inode. When the parent is already in the delta layer,
// we can use it directly - all its ancestors are guaranteed to exist in delta
// (a directory can only be in delta if its parents are too). This avoids the
// expensive ensure_parent_dirs() walk which would otherwise check each path
// component against both delta and base layers.
let delta_parent_ino = if parent_info.layer == Layer::Delta {
parent_info.underlying_ino
} else {
// Walk delta to find parent
// Parent is in base layer - we need to create the directory hierarchy in
// delta before we can create the new entry. This walks the path and creates
// any missing directories.
self.ensure_parent_dirs(&path, uid, gid).await?;
let mut ino: i64 = 1;
for comp in parent_info.path.split('/').filter(|s| !s.is_empty()) {
if let Some(s) = FileSystem::lookup(&self.delta, ino, comp).await? {
Expand Down Expand Up @@ -954,13 +969,18 @@ impl FileSystem for OverlayFS {
// Remove whiteout if exists
self.remove_whiteout(&path).await?;

// Ensure parent dirs exist in delta
self.ensure_parent_dirs(&path, uid, gid).await?;

// Get delta parent inode
// Resolve the delta parent inode. When the parent is already in the delta layer,
// we can use it directly - all its ancestors are guaranteed to exist in delta
// (a directory can only be in delta if its parents are too). This avoids the
// expensive ensure_parent_dirs() walk which would otherwise check each path
// component against both delta and base layers.
let delta_parent_ino = if parent_info.layer == Layer::Delta {
parent_info.underlying_ino
} else {
// Parent is in base layer - we need to create the directory hierarchy in
// delta before we can create the new file. This walks the path and creates
// any missing directories.
self.ensure_parent_dirs(&path, uid, gid).await?;
let mut ino: i64 = 1;
for comp in parent_info.path.split('/').filter(|s| !s.is_empty()) {
if let Some(s) = FileSystem::lookup(&self.delta, ino, comp).await? {
Expand Down Expand Up @@ -993,11 +1013,15 @@ impl FileSystem for OverlayFS {
let path = self.build_path(parent_ino, name)?;

self.remove_whiteout(&path).await?;
self.ensure_parent_dirs(&path, uid, gid).await?;

// Resolve the delta parent inode. When the parent is already in the delta layer,
// we can use it directly - all its ancestors are guaranteed to exist in delta.
// This avoids the expensive ensure_parent_dirs() walk.
let delta_parent_ino = if parent_info.layer == Layer::Delta {
parent_info.underlying_ino
} else {
// Parent is in base layer - create the directory hierarchy in delta first.
self.ensure_parent_dirs(&path, uid, gid).await?;
let mut ino: i64 = 1;
for comp in parent_info.path.split('/').filter(|s| !s.is_empty()) {
if let Some(s) = FileSystem::lookup(&self.delta, ino, comp).await? {
Expand Down Expand Up @@ -1034,11 +1058,15 @@ impl FileSystem for OverlayFS {
let path = self.build_path(parent_ino, name)?;

self.remove_whiteout(&path).await?;
self.ensure_parent_dirs(&path, uid, gid).await?;

// Resolve the delta parent inode. When the parent is already in the delta layer,
// we can use it directly - all its ancestors are guaranteed to exist in delta.
// This avoids the expensive ensure_parent_dirs() walk.
let delta_parent_ino = if parent_info.layer == Layer::Delta {
parent_info.underlying_ino
} else {
// Parent is in base layer - create the directory hierarchy in delta first.
self.ensure_parent_dirs(&path, uid, gid).await?;
let mut ino: i64 = 1;
for comp in parent_info.path.split('/').filter(|s| !s.is_empty()) {
if let Some(s) = FileSystem::lookup(&self.delta, ino, comp).await? {
Expand Down Expand Up @@ -1172,12 +1200,15 @@ impl FileSystem for OverlayFS {
};

self.remove_whiteout(&new_path).await?;
self.ensure_parent_dirs(&new_path, 0, 0).await?;

// Get delta parent
// Resolve the delta parent inode for the new link location. When the parent is
// already in the delta layer, we can use it directly - all its ancestors are
// guaranteed to exist in delta. This avoids the expensive ensure_parent_dirs() walk.
let delta_parent_ino = if parent_info.layer == Layer::Delta {
parent_info.underlying_ino
} else {
// Parent is in base layer - create the directory hierarchy in delta first.
self.ensure_parent_dirs(&new_path, 0, 0).await?;
let mut ino: i64 = 1;
for comp in parent_info.path.split('/').filter(|s| !s.is_empty()) {
if let Some(s) = FileSystem::lookup(&self.delta, ino, comp).await? {
Expand Down Expand Up @@ -1246,12 +1277,15 @@ impl FileSystem for OverlayFS {

// Remove whiteout at destination
self.remove_whiteout(&new_path).await?;
self.ensure_parent_dirs(&new_path, 0, 0).await?;

// Get delta destination parent
// Resolve the delta destination parent inode. When the parent is already in the
// delta layer, we can use it directly - all its ancestors are guaranteed to exist
// in delta. This avoids the expensive ensure_parent_dirs() walk.
let delta_dst_parent_ino = if new_parent_info.layer == Layer::Delta {
new_parent_info.underlying_ino
} else {
// Destination parent is in base layer - create the directory hierarchy in delta first.
self.ensure_parent_dirs(&new_path, 0, 0).await?;
let mut ino: i64 = 1;
for comp in new_parent_info.path.split('/').filter(|s| !s.is_empty()) {
if let Some(s) = FileSystem::lookup(&self.delta, ino, comp).await? {
Expand Down
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