VFS FIFO: Enlarge FIFO buffer sizes

* Increase FIFO buffer capacity from 32 to 64 KiB and the FIFO atomic
  write size ({BUF_SIZE}) from 512 bytes to 4 KiB (both like Linux).
* Fix *pathconf(..., _PC_PIPE_BUF). It was returning 4 KiB although the
  implemented atomic write size was 512 bytes only. Now both *pathconf()
  and the FIFO implementation refer to the same constant.

headers/private/system/vfs_defs.h

@@ -1,6 +1,7 @@
 /*
- * Copyright 2002-2008, Axel Dörfler, [email protected]. All rights reserved.
+ * Copyright 2002-2008, Axel Dörfler, [email protected].
- * Distributed under the terms of the MIT License.
+ * Copyright 2013, Ingo Weinhold, [email protected]e.
+ * All rights reserved. Distributed under the terms of the MIT License.
  *
  * Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
  * Distributed under the terms of the NewOS License.
@@ -8,6 +9,8 @@
 #ifndef _SYSTEM_VFS_DEFS_H
 #define _SYSTEM_VFS_DEFS_H
 
+
+#include <limits.h>
 #include <sys/stat.h>
 
 #include <SupportDefs.h>
@@ -20,4 +23,18 @@ struct fd_info {
 	ino_t	node;
 };
 
+
+/* maximum write size to a pipe/FIFO that is guaranteed not to be interleaved
+   with other writes (aka {PIPE_BUF}; must be >= _POSIX_PIPE_BUF) */
+#define VFS_FIFO_ATOMIC_WRITE_SIZE	(4 * 1024)
+
+/* pipe/FIFO buffer capacity */
+#define VFS_FIFO_BUFFER_CAPACITY	(64 * 1024)
+
+// make sure the constant values are sane
+#if VFS_FIFO_ATOMIC_WRITE_SIZE < _POSIX_PIPE_BUF
+#	error VFS_FIFO_ATOMIC_WRITE_SIZE < _POSIX_PIPE_BUF!
+#endif
+
+
 #endif	/* _SYSTEM_VFS_DEFS_H */

src/system/kernel/fs/fifo.cpp

@@ -30,6 +30,7 @@
 #include <util/AutoLock.h>
 #include <util/ring_buffer.h>
 #include <vfs.h>
+#include <vfs_defs.h>
 #include <vm/vm.h>
 
 
@@ -42,11 +43,6 @@
 
 
 #define PIPEFS_HASH_SIZE		16
-#define PIPEFS_MAX_BUFFER_SIZE	32768
-
-
-// TODO: PIPE_BUF is supposed to be defined somewhere else.
-#define PIPE_BUF	_POSIX_PIPE_BUF
 
 
 namespace fifo {
@@ -252,7 +248,7 @@ RingBuffer::CreateBuffer()
 	if (fBuffer != NULL)
 		return B_OK;
 
-	fBuffer = create_ring_buffer(PIPEFS_MAX_BUFFER_SIZE);
+	fBuffer = create_ring_buffer(VFS_FIFO_BUFFER_CAPACITY);
 	return fBuffer != NULL ? B_OK : B_NO_MEMORY;
 }
 
@@ -376,10 +372,10 @@ Inode::WriteDataToBuffer(const void* _data, size_t* _length, bool nonBlocking)
 	TRACE("Inode %p::WriteDataToBuffer(data = %p, bytes = %zu)\n", this, data,
 		dataSize);
 
-	// According to the standard, request up to PIPE_BUF bytes shall not be
+	// A request up to VFS_FIFO_ATOMIC_WRITE_SIZE bytes shall not be
 	// interleaved with other writer's data.
 	size_t minToWrite = 1;
-	if (dataSize <= PIPE_BUF)
+	if (dataSize <= VFS_FIFO_ATOMIC_WRITE_SIZE)
 		minToWrite = dataSize;
 
 	while (dataSize > 0) {

src/system/libroot/posix/unistd/conf.cpp

@@ -24,6 +24,7 @@
 #include <thread_defs.h>
 #include <user_group.h>
 #include <user_timer_defs.h>
+#include <vfs_defs.h>
 
 #include <errno_private.h>
 #include <libroot_private.h>
@@ -257,7 +258,7 @@ __pathconf_common(struct statvfs *fs, struct stat *st,
 			return PATH_MAX;
 
 		case _PC_PIPE_BUF:
-			return 4096;
+			return VFS_FIFO_ATOMIC_WRITE_SIZE;
 
 		case _PC_LINK_MAX:
 			return LINK_MAX;