utilioprio: Add Windows support as ioprio_set_file_idle

configure.ac

@@ -983,6 +983,31 @@ else
 fi
 AC_DEFINE_UNQUOTED([HAVE_IOPRIO_SYSCALL], [$HAVE_IOPRIO_SYSCALL], [Define to 1 if Linux ioprio syscalls are usable.])
 
+AC_MSG_CHECKING(for Windows file I/O priority functions)
+AC_COMPILE_IFELSE([
+  AC_LANG_PROGRAM([[
+    #define _WIN32_WINNT 0x0600
+    #include <windows.h>
+    #include <io.h>
+    #include <stdio.h>
+  ]],[[
+    static const FILE_IO_PRIORITY_HINT_INFO priorityHint = {
+        .PriorityHint = IoPriorityHintLow,
+    };
+    FILE * const F = fopen("test", "r");
+    HANDLE hFile = _get_osfhandle(_fileno(F));
+
+    SetFileInformationByHandle(hFile, FileIoPriorityHintInfo, &priorityHint, sizeof(priorityHint));
+  ]])
+],[
+  have_windows_ioprio=yes
+  AC_DEFINE(HAVE_WINDOWS_IOPRIO,1,[Define this symbol if you have Windows I/O priority functions])
+],[
+  have_windows_ioprio=no
+])
+AC_MSG_RESULT($have_windows_ioprio)
+AM_CONDITIONAL([HAVE_WINDOWS_IOPRIO], [test "$have_windows_ioprio" = "yes"])
+
 dnl Check for different ways of gathering OS randomness
 AC_MSG_CHECKING([for Linux getrandom function])
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[

src/node/blockstorage.cpp

@@ -1049,6 +1049,8 @@ bool BlockManager::ReadBlockFromDisk(CBlock& block, const FlatFilePos& pos, cons
         return false;
     }
 
+    filein.SetIdlePriority();
+
     // Read block
     try {
         filein >> TX_WITH_WITNESS(block);

src/streams.cpp

@@ -5,6 +5,7 @@
 #include <span.h>
 #include <streams.h>
 #include <util/fs_helpers.h>
+#include <util/ioprio.h>
 
 #include <array>
 
@@ -106,6 +107,11 @@ bool AutoFile::Commit()
     return ::FileCommit(m_file);
 }
 
+void AutoFile::SetIdlePriority()
+{
+    ioprio_set_file_idle(m_file);
+}
+
 bool AutoFile::IsError()
 {
     return ferror(m_file);

src/streams.h

@@ -455,6 +455,7 @@ public:
     }
 
     bool Commit();
+    void SetIdlePriority();
     bool IsError();
     bool Truncate(unsigned size);
 };

src/util/ioprio.cpp

@@ -55,3 +55,25 @@ int ioprio_set_idle() {
 }
 
 #endif
+
+
+#ifdef HAVE_WINDOWS_IOPRIO
+
+#ifdef _WIN32_WINNT
+#undef _WIN32_WINNT
+#endif
+#define _WIN32_WINNT 0x0600
+
+#include <windows.h>
+#include <io.h>
+
+bool ioprio_set_file_idle(FILE * const F) {
+    static const FILE_IO_PRIORITY_HINT_INFO priorityHint = {
+        .PriorityHint = IoPriorityHintLow,
+    };
+    HANDLE hFile = _get_osfhandle(_fileno(F));
+
+    return SetFileInformationByHandle(hFile, FileIoPriorityHintInfo, &priorityHint, sizeof(priorityHint));
+}
+
+#endif

src/util/ioprio.h

@@ -54,4 +54,10 @@ public:
 #define IOPRIO_IDLER(lowprio)  (void)lowprio;
 #endif
 
+#ifdef HAVE_WINDOWS_IOPRIO
+bool ioprio_set_file_idle(FILE *);
+#else
+#define ioprio_set_file_idle(f)  ((void)false)
+#endif
+
 #endif // BITCOIN_UTIL_IOPRIO_H