[PATCH] D115416: [lld-macho] Prevent writing map files on the critical path

[Vincent Lee via Phabricator via llvm-commits]

thevinster updated this revision to Diff 394103.
thevinster added a comment.

Show two different ways of using threadPool


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D115416/new/

https://reviews.llvm.org/D115416

Files:
  lld/MachO/Writer.cpp


Index: lld/MachO/Writer.cpp
===================================================================
--- lld/MachO/Writer.cpp
+++ lld/MachO/Writer.cpp
@@ -29,6 +29,7 @@
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/Parallel.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/ThreadPool.h"
 #include "llvm/Support/TimeProfiler.h"
 #include "llvm/Support/xxhash.h"
 
@@ -64,6 +65,7 @@
 
   template <class LP> void run();
 
+  ThreadPool writerThreadPool;
   std::unique_ptr<FileOutputBuffer> &buffer;
   uint64_t addr = 0;
   uint64_t fileOff = 0;
@@ -1035,10 +1037,17 @@
       dataInCodeSection,
       functionStartsSection,
   };
-  parallelForEach(linkEditSections, [](LinkEditSection *osec) {
-    if (osec)
-      osec->finalizeContents();
-  });
+  SmallVector<std::shared_future<void>> threadFutures;
+  for (LinkEditSection *osec : linkEditSections) {
+    threadFutures.emplace_back(writerThreadPool.async(
+        [](LinkEditSection *osec) {
+          if (osec)
+            osec->finalizeContents();
+        },
+        osec));
+  }
+  for (std::shared_future<void> &future : threadFutures)
+    future.wait();
 
   // Now that __LINKEDIT is filled out, do a proper calculation of its
   // addresses and offsets.
@@ -1091,14 +1100,19 @@
 // values.
 void Writer::writeUuid() {
   TimeTraceScope timeScope("Computing UUID");
+  ThreadPool writeUuidThreadPool;
+
   ArrayRef<uint8_t> data{buffer->getBufferStart(), buffer->getBufferEnd()};
   unsigned chunkCount = parallel::strategy.compute_thread_count() * 10;
   // Round-up integer division
   size_t chunkSize = (data.size() + chunkCount - 1) / chunkCount;
   std::vector<ArrayRef<uint8_t>> chunks = split(data, chunkSize);
   std::vector<uint64_t> hashes(chunks.size());
-  parallelForEachN(0, chunks.size(),
-                   [&](size_t i) { hashes[i] = xxHash64(chunks[i]); });
+  for (size_t i = 0; i < chunks.size(); ++i)
+    writeUuidThreadPool.async(
+        [&](size_t i) { hashes[i] = xxHash64(chunks[i]); }, i);
+  writeUuidThreadPool.wait();
+
   uint64_t digest = xxHash64({reinterpret_cast<uint8_t *>(hashes.data()),
                               hashes.size() * sizeof(uint64_t)});
   uuidCommand->writeUuid(digest);
@@ -1147,8 +1161,8 @@
   sortSegmentsAndSections();
   createLoadCommands<LP>();
   finalizeAddresses();
+  writerThreadPool.async(writeMapFile);
   finalizeLinkEditSegment();
-  writeMapFile();
   writeOutputFile();
 }
 


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