src: cache continuation_data pointer in MKDirpSync

benchmark/fs/bench-mkdirpSync.js

@@ -0,0 +1,27 @@
+'use strict';
+
+// Benchmarks MKDirpSync (fs.mkdirSync with recursive: true), which iterates
+// over a continuation_data path queue. Varying depth exercises the inner loop
+// more, making the continuation_data pointer cache more impactful.
+
+const common = require('../common');
+const fs = require('fs');
+const path = require('path');
+const tmpdir = require('../../test/common/tmpdir');
+tmpdir.refresh();
+
+const bench = common.createBenchmark(main, {
+  n: [1e3],
+  depth: [4, 8, 16],
+});
+
+let dirc = 0;
+
+function main({ n, depth }) {
+  bench.start();
+  for (let i = 0; i < n; i++) {
+    const parts = Array.from({ length: depth }, () => String(++dirc));
+    fs.mkdirSync(path.join(tmpdir.path, ...parts), { recursive: true });
+  }
+  bench.end(n);
+}

benchmark/streams/writable-writev-string.js

@@ -0,0 +1,42 @@
+'use strict';
+
+const common = require('../common.js');
+const { Writable } = require('stream');
+
+// Benchmarks StreamBase::Writev with string chunks, exercising the chunk
+// cache that avoids redundant V8 array accesses, ToString, and ParseEncoding
+// calls between the sizing pass and the write pass.
+const bench = common.createBenchmark(main, {
+  n: [1e4],
+  chunks: [4, 16, 64],
+  encoding: ['utf8', 'latin1'],
+  type: ['string', 'buffer', 'mixed'],
+});
+
+function main({ n, chunks, encoding, type }) {
+  const str = 'Hello, benchmark! '.repeat(4);
+  const buf = Buffer.from(str, encoding);
+
+  const wr = new Writable({
+    writev(chunks, cb) { cb(); },
+    write(chunk, enc, cb) { cb(); },
+  });
+
+  bench.start();
+  for (let i = 0; i < n; i++) {
+    wr.cork();
+    for (let j = 0; j < chunks; j++) {
+      if (type === 'buffer') {
+        wr.write(buf);
+      } else if (type === 'string') {
+        wr.write(str, encoding);
+      } else {
+        // Alternate buffer and string to hit the mixed (non-all_buffers) path.
+        if (j % 2 === 0) wr.write(buf);
+        else wr.write(str, encoding);
+      }
+    }
+    wr.uncork();
+  }
+  bench.end(n);
+}

src/node_file.cc

@@ -1866,16 +1866,17 @@ int MKDirpSync(uv_loop_t* loop,
     req_wrap->continuation_data()->PushPath(std::move(path));
   }
 
-  while (req_wrap->continuation_data()->paths().size() > 0) {
-    std::string next_path = req_wrap->continuation_data()->PopPath();
+  FSContinuationData* cont_data = req_wrap->continuation_data();
+  while (cont_data->paths().size() > 0) {
+    std::string next_path = cont_data->PopPath();
     int err = uv_fs_mkdir(loop, req, next_path.c_str(), mode, nullptr);
     while (true) {
       switch (err) {
         // Note: uv_fs_req_cleanup in terminal paths will be called by
         // ~FSReqWrapSync():
         case 0:
-          req_wrap->continuation_data()->MaybeSetFirstPath(next_path);
-          if (req_wrap->continuation_data()->paths().empty()) {
+          cont_data->MaybeSetFirstPath(next_path);
+          if (cont_data->paths().empty()) {
             return 0;
           }
           break;
@@ -1889,9 +1890,9 @@ int MKDirpSync(uv_loop_t* loop,
           std::string dirname =
               next_path.substr(0, next_path.find_last_of(kPathSeparator));
           if (dirname != next_path) {
-            req_wrap->continuation_data()->PushPath(std::move(next_path));
-            req_wrap->continuation_data()->PushPath(std::move(dirname));
-          } else if (req_wrap->continuation_data()->paths().empty()) {
+            cont_data->PushPath(std::move(next_path));
+            cont_data->PushPath(std::move(dirname));
+          } else if (cont_data->paths().empty()) {
             err = UV_EEXIST;
             continue;
           }
@@ -1903,8 +1904,7 @@ int MKDirpSync(uv_loop_t* loop,
           err = uv_fs_stat(loop, req, next_path.c_str(), nullptr);
           if (err == 0 && !S_ISDIR(req->statbuf.st_mode)) {
             uv_fs_req_cleanup(req);
-            if (orig_err == UV_EEXIST &&
-                req_wrap->continuation_data()->paths().size() > 0) {
+            if (orig_err == UV_EEXIST && cont_data->paths().size() > 0) {
               return UV_ENOTDIR;
             }
             return UV_EEXIST;

src/stream_base.cc

@@ -201,12 +201,24 @@ int StreamBase::Writev(const FunctionCallbackInfo<Value>& args) {
   size_t offset;
 
   if (!all_buffers) {
+    // Cache per-chunk data from the first pass so the second pass avoids
+    // redundant V8 array accesses, ToString conversions, and ParseEncoding
+    // calls. Local<> handles remain valid for the duration of this scope.
+    struct CachedChunk {
+      Local<Value> value;
+      Local<String> string;  // empty for Buffer chunks
+      enum encoding enc;
+    };
+    MaybeStackBuffer<CachedChunk, 16> chunk_cache(count);
+
     // Determine storage size first
     for (size_t i = 0; i < count; i++) {
       Local<Value> chunk;
       if (!chunks->Get(context, i * 2).ToLocal(&chunk))
         return -1;
 
+      chunk_cache[i].value = chunk;
+
       if (Buffer::HasInstance(chunk))
         continue;
         // Buffer chunk, no additional storage required
@@ -219,6 +231,8 @@ int StreamBase::Writev(const FunctionCallbackInfo<Value>& args) {
       if (!chunks->Get(context, i * 2 + 1).ToLocal(&next_chunk))
         return -1;
       enum encoding encoding = ParseEncoding(isolate, next_chunk);
+      chunk_cache[i].string = string;
+      chunk_cache[i].enc = encoding;
       size_t chunk_size;
       if ((encoding == UTF8 &&
              string->Length() > 65535 &&
@@ -232,33 +246,20 @@ int StreamBase::Writev(const FunctionCallbackInfo<Value>& args) {
 
     if (storage_size > INT_MAX)
       return UV_ENOBUFS;
-  } else {
-    for (size_t i = 0; i < count; i++) {
-      Local<Value> chunk;
-      if (!chunks->Get(context, i).ToLocal(&chunk))
-        return -1;
-      bufs[i].base = Buffer::Data(chunk);
-      bufs[i].len = Buffer::Length(chunk);
-    }
-  }
 
-  std::unique_ptr<BackingStore> bs;
-  if (storage_size > 0) {
-    bs = ArrayBuffer::NewBackingStore(
-        isolate, storage_size, BackingStoreInitializationMode::kUninitialized);
-  }
+    std::unique_ptr<BackingStore> bs;
+    if (storage_size > 0) {
+      bs = ArrayBuffer::NewBackingStore(
+          isolate, storage_size, BackingStoreInitializationMode::kUninitialized);
+    }
 
-  offset = 0;
-  if (!all_buffers) {
+    offset = 0;
     for (size_t i = 0; i < count; i++) {
-      Local<Value> chunk;
-      if (!chunks->Get(context, i * 2).ToLocal(&chunk))
-        return -1;
-
-      // Write buffer
-      if (Buffer::HasInstance(chunk)) {
-        bufs[i].base = Buffer::Data(chunk);
-        bufs[i].len = Buffer::Length(chunk);
+      // string.IsEmpty() signals a Buffer chunk; enc is uninitialised in
+      // that case so we must not read it.
+      if (chunk_cache[i].string.IsEmpty()) {
+        bufs[i].base = Buffer::Data(chunk_cache[i].value);
+        bufs[i].len = Buffer::Length(chunk_cache[i].value);
         continue;
       }
 
@@ -268,28 +269,33 @@ int StreamBase::Writev(const FunctionCallbackInfo<Value>& args) {
           static_cast<char*>(bs ? bs->Data() : nullptr) + offset;
       size_t str_size = (bs ? bs->ByteLength() : 0) - offset;
 
-      Local<String> string;
-      if (!chunk->ToString(context).ToLocal(&string))
-        return -1;
-      Local<Value> next_chunk;
-      if (!chunks->Get(context, i * 2 + 1).ToLocal(&next_chunk))
-        return -1;
-      enum encoding encoding = ParseEncoding(isolate, next_chunk);
       str_size = StringBytes::Write(isolate,
                                     str_storage,
                                     str_size,
-                                    string,
-                                    encoding);
+                                    chunk_cache[i].string,
+                                    chunk_cache[i].enc);
       bufs[i].base = str_storage;
       bufs[i].len = str_size;
       offset += str_size;
     }
+
+    StreamWriteResult res = Write(*bufs, count, nullptr, req_wrap_obj);
+    SetWriteResult(res);
+    if (res.wrap != nullptr && storage_size > 0)
+      res.wrap->SetBackingStore(std::move(bs));
+    return res.err;
+  } else {
+    for (size_t i = 0; i < count; i++) {
+      Local<Value> chunk;
+      if (!chunks->Get(context, i).ToLocal(&chunk))
+        return -1;
+      bufs[i].base = Buffer::Data(chunk);
+      bufs[i].len = Buffer::Length(chunk);
+    }
   }
 
   StreamWriteResult res = Write(*bufs, count, nullptr, req_wrap_obj);
   SetWriteResult(res);
-  if (res.wrap != nullptr && storage_size > 0)
-    res.wrap->SetBackingStore(std::move(bs));
   return res.err;
 }