[lld] [llvm] [lld][MachO] Follow-up to use madvise() for threaded file page-in. (PR #157917)

[Ellis Hoag via llvm-commits]

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@@ -330,61 +336,65 @@ class SerialBackgroundQueue {
   }
 };
 
+static SerialBackgroundWorkQueue pageInQueue;
+
 // Most input files have been mapped but not yet paged in.
 // This code forces the page-ins on multiple threads so
 // the process is not stalled waiting on disk buffer i/o.
 void multiThreadedPageInBackground(DeferredFiles &deferred) {
+  using namespace std::chrono;
   static const size_t pageSize = Process::getPageSizeEstimate();
   static const size_t largeArchive = 10 * 1024 * 1024;
-#ifndef NDEBUG
-  using namespace std::chrono;
-  std::atomic_int numDeferedFilesTouched = 0;
   static std::atomic_uint64_t totalBytes = 0;
+  std::atomic_int numDeferedFilesAdvised = 0;
   auto t0 = high_resolution_clock::now();
-#endif
 
   auto preloadDeferredFile = [&](const DeferredFile &deferredFile) {
     const StringRef &buff = deferredFile.buffer.getBuffer();
     if (buff.size() > largeArchive)
       return;
-#ifndef NDEBUG
+
     totalBytes += buff.size();
-    numDeferedFilesTouched += 1;
-#endif
+    numDeferedFilesAdvised += 1;
 
+#if _WIN32
     // Reference all file's mmap'd pages to load them into memory.
-    for (const char *page = buff.data(), *end = page + buff.size(); page < end;
-         page += pageSize) {
+    for (const char *page = buff.data(), *end = page + buff.size();
+         page < end && !pageInQueue.stopAllWork; page += pageSize) {
       LLVM_ATTRIBUTE_UNUSED volatile char t = *page;
       (void)t;
     }
+#else
+#define DEBUG_TYPE "lld-madvise"
+    auto aligned = llvm::alignAddr(buff.data(), Align(pageSize));
+    if (madvise((void *)aligned, buff.size(), MADV_WILLNEED) < 0)
+      LLVM_DEBUG(llvm::dbgs() << "madvise error: " << strerror(errno) << "\n");
+#undef DEBUG_TYPE
+#endif
   };
-#if LLVM_ENABLE_THREADS
-  { // Create scope for waiting for the taskGroup
+
+  if (llvm_is_multithreaded()) { // Create scope for waiting for the taskGroup
     std::atomic_size_t index = 0;
     llvm::parallel::TaskGroup taskGroup;
     for (int w = 0; w < config->readWorkers; w++)
       taskGroup.spawn([&index, &preloadDeferredFile, &deferred]() {
-        while (true) {
+        while (!pageInQueue.stopAllWork) {
           size_t localIndex = index.fetch_add(1);
           if (localIndex >= deferred.size())
             break;
           preloadDeferredFile(deferred[localIndex]);
         }
       });
   }
-#endif
-#ifndef NDEBUG
+
   auto dt = high_resolution_clock::now() - t0;
   if (Process::GetEnv("LLD_MULTI_THREAD_PAGE"))
     llvm::dbgs() << "multiThreadedPageIn " << totalBytes << "/"
-                 << numDeferedFilesTouched << "/" << deferred.size() << "/"
+                 << numDeferedFilesAdvised << "/" << deferred.size() << "/"
                  << duration_cast<milliseconds>(dt).count() / 1000. << "\n";
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ellishg wrote:

Shouldn't this still be guarded by `NDEBUG`? We don't want to waste time reading the environment on release builds.

https://github.com/llvm/llvm-project/pull/157917