Added a small test application that uses the same allocation group algorithm

as (our) BFS, so that you can play with it.


git-svn-id: file:///srv/svn/repos/haiku/trunk/current@6340 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/tests/add-ons/kernel/file_systems/bfs/mkbfs/Jamfile

@@ -20,8 +20,7 @@ UsePrivateHeaders [ FDirName kernel util ] ;
 	SubDirC++Flags $(defines) -fno-exceptions -fno-rtti $(malloc_debug_flags) ;
 }
 
-SimpleTest mkbfs
-	:
+SimpleTest mkbfs :
 	mkbfs.cpp
 
 	cache.c
@@ -36,6 +35,10 @@ SimpleTest mkbfs
 	:
 	;
 
+SimpleTest allocationGroups :
+	allocationGroups.cpp
+	;
+
 # Tell Jam where to find these sources
 SEARCH on [ FGristFiles
 		Volume.cpp BPlusTree.cpp Inode.cpp Index.cpp Query.cpp Journal.cpp

src/tests/add-ons/kernel/file_systems/bfs/mkbfs/allocationGroups.cpp

@@ -0,0 +1,70 @@
+/* 
+** Copyright 2004, Axel Dörfler, [email protected]. All rights reserved.
+** Distributed under the terms of the OpenBeOS License.
+*/
+
+
+#include <SupportDefs.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+
+static const uint32 kDesiredAllocationGroups = 56;
+
+
+int
+main(int argc, char **argv)
+{
+	if (argc != 3 || !isdigit(argv[1][0]) || !isdigit(argv[2][0])) {
+		const char *name = strrchr(argv[0], '/');
+		name = name ? name + 1 : argv[0];
+
+		fprintf(stderr, "usage: %s <num blocks> <block size>\n", name);
+		return -1;
+	}
+
+	off_t numBlocks = atoll(argv[1]);
+	uint32 blockSize = (uint32)atol(argv[2]);
+
+	if (blockSize != 1024 && blockSize != 2048 && blockSize != 4096 && blockSize != 8192) {
+		fprintf(stderr, "valid values for <block size> are: 1024, 2048, 4096, 8192\n");
+		return -1;
+	}
+
+	uint32 blocks_per_ag = 1;
+	uint32 ag_shift = 13;
+	uint32 num_ags = 0;
+
+	uint32 bitsPerBlock = blockSize << 3;
+	off_t bitmapBlocks = (numBlocks + bitsPerBlock - 1) / bitsPerBlock;
+	for (uint32 i = 8192; i < bitsPerBlock; i *= 2) {
+		ag_shift++;
+	}
+
+	// Many allocation groups help applying allocation policies, but if
+	// they are too small, we will need to many block_runs to cover large
+	// files
+
+	while (true) {
+		num_ags = bitmapBlocks / blocks_per_ag;
+		if (num_ags > kDesiredAllocationGroups) {
+			if (ag_shift == 16)
+				break;
+
+			ag_shift++;
+			blocks_per_ag++;
+		} else
+			break;
+	}
+
+	printf("bitmap blocks = %Ld\n", bitmapBlocks);
+	printf("allocation groups = %lu\n", num_ags);
+	printf("shift = %lu (%lu)\n", ag_shift, 1UL << ag_shift);
+	printf("blocks per group = %lu\n", blocks_per_ag);
+
+	return 0;
+}
+