Use build tag requiring Linux on EN for fadvise

ledger/complete/wal/fadvise.go

@@ -1,44 +1,25 @@
-package wal
-
-import (
-	"runtime"
+//go:build !linux
+// +build !linux
 
-	"golang.org/x/sys/unix"
-)
+package wal
 
-// fadviseNoLinuxPageCache advises Linux to evict
+// fadviseNoLinuxPageCache does nothing if GOOS != "linux".
+// Otherwise, fadviseNoLinuxPageCache advises Linux to evict
 // a file from Linux page cache.  This calls unix.Fadvise which
 // in turn calls posix_fadvise with POSIX_FADV_DONTNEED.
-// If GOOS != "linux" then this function does nothing.
 // CAUTION: If fsync=true, this will call unix.Fsync which
 // can cause performance hit especially when used inside a loop.
 func fadviseNoLinuxPageCache(fd uintptr, fsync bool) error {
-	return fadviseSegmentNoLinuxPageCache(fd, 0, 0, fsync)
+	return nil
 }
 
-// fadviseSegmentNoLinuxPageCache advises Linux to evict the
+// fadviseNoLinuxPageCache does nothing if GOOS != "linux".
+// Otherwise, fadviseSegmentNoLinuxPageCache advises Linux to evict
 // file segment from Linux page cache.  This calls unix.Fadvise
 // which in turn calls posix_fadvise with POSIX_FADV_DONTNEED.
 // If GOOS != "linux" then this function does nothing.
 // CAUTION: If fsync=true, this will call unix.Fsync which
 // can cause performance hit especially when used inside a loop.
 func fadviseSegmentNoLinuxPageCache(fd uintptr, off, len int64, fsync bool) error {
-	if runtime.GOOS != "linux" {
-		return nil
-	}
-
-	// Optionally call fsync because dirty pages won't be evicted.
-	if fsync {
-		_ = unix.Fsync(int(fd)) // ignore error because this is optional
-	}
-
-	// Fadvise under the hood calls posix_fadvise.
-	// posix_fadvise doc from man page says:
-	// "posix_fadvise - predeclare an access pattern for file data"
-	// "The advice applies to a (not necessarily existent) region
-	// starting at offset and extending for len bytes (or until
-	// the end of the file if len is 0) within the file referred
-	// to by fd.  The advice is not binding; it merely constitutes
-	// an expectation on behalf of the application."
-	return unix.Fadvise(int(fd), off, len, unix.FADV_DONTNEED)
+	return nil
 }

ledger/complete/wal/fadvise_linux.go

@@ -0,0 +1,41 @@
+//go:build linux
+// +build linux
+
+package wal
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+// fadviseNoLinuxPageCache advises Linux to evict
+// a file from Linux page cache.  This calls unix.Fadvise which
+// in turn calls posix_fadvise with POSIX_FADV_DONTNEED.
+// If GOOS != "linux" then this function does nothing.
+// CAUTION: If fsync=true, this will call unix.Fsync which
+// can cause performance hit especially when used inside a loop.
+func fadviseNoLinuxPageCache(fd uintptr, fsync bool) error {
+	return fadviseSegmentNoLinuxPageCache(fd, 0, 0, fsync)
+}
+
+// fadviseSegmentNoLinuxPageCache advises Linux to evict the
+// file segment from Linux page cache.  This calls unix.Fadvise
+// which in turn calls posix_fadvise with POSIX_FADV_DONTNEED.
+// If GOOS != "linux" then this function does nothing.
+// CAUTION: If fsync=true, this will call unix.Fsync which
+// can cause performance hit especially when used inside a loop.
+func fadviseSegmentNoLinuxPageCache(fd uintptr, off, len int64, fsync bool) error {
+	// Optionally call fsync because dirty pages won't be evicted.
+	if fsync {
+		_ = unix.Fsync(int(fd)) // ignore error because this is optional
+	}
+
+	// Fadvise under the hood calls posix_fadvise.
+	// posix_fadvise doc from man page says:
+	// "posix_fadvise - predeclare an access pattern for file data"
+	// "The advice applies to a (not necessarily existent) region
+	// starting at offset and extending for len bytes (or until
+	// the end of the file if len is 0) within the file referred
+	// to by fd.  The advice is not binding; it merely constitutes
+	// an expectation on behalf of the application."
+	return unix.Fadvise(int(fd), off, len, unix.FADV_DONTNEED)
+}