Optimizations for Windows

- Set opt_lg_chunk based on run-time OS setting
- Verify LG_PAGE is compatible with run-time OS setting
- When targeting Windows Vista or newer, use SRWLOCK instead of CRITICAL_SECTION
- When targeting Windows Vista or newer, statically initialize init_lock

src/chunk.c

@@ -5,7 +5,7 @@
 /* Data. */
 
 const char	*opt_dss = DSS_DEFAULT;
-size_t		opt_lg_chunk = LG_CHUNK_DEFAULT;
+size_t		opt_lg_chunk = 0;
 
 /* Used exclusively for gdump triggering. */
 static size_t	curchunks;
@@ -535,6 +535,21 @@ chunks_rtree_node_alloc(size_t nelms)
 bool
 chunk_boot(void)
 {
+#ifdef _WIN32
+	SYSTEM_INFO info;
+	GetSystemInfo(&info);
+
+	/* Verify actual page size is equal to or an integral multiple of configured page size */
+	if (info.dwPageSize & ((1U << LG_PAGE) - 1))
+		return (true);
+
+	/* Configure chunksize (if not set) to match granularity (usually 64K), so pages_map will always take fast path */
+	if (!opt_lg_chunk)
+		opt_lg_chunk = ffs((int)info.dwAllocationGranularity) - 1;
+#else
+	if (!opt_lg_chunk)
+		opt_lg_chunk = LG_CHUNK_DEFAULT;
+#endif
 
 	/* Set variables according to the value of opt_lg_chunk. */
 	chunksize = (ZU(1) << opt_lg_chunk);