libext2fs: allow the default journal size to go as large as a gigabyte

Recent research has shown that for a metadata-heavy workload, a 128 MB
is journal be a bottleneck on HDD's, and that the optimal journal size
is proportional to number of unique metadata blocks that can be
modified (and written into the journal) in a 30 second window.  One
gigabyte should be sufficient for most workloads, which will be used
for file systems larger than 128 gigabytes.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/lib/ext2fs/mkjournal.c b/lib/ext2fs/mkjournal.c
index 43ffa53..7f78291 100644 (file)
--- a/lib/ext2fs/mkjournal.c
+++ b/lib/ext2fs/mkjournal.c
@@ -334,20 +334,28 @@ out2:
  * Find a reasonable journal file size (in blocks) given the number of blocks
  * in the filesystem.  For very small filesystems, it is not reasonable to
  * have a journal that fills more than half of the filesystem.
+ *
+ * n.b. comments assume 4k blocks
  */
 int ext2fs_default_journal_size(__u64 num_blocks)
 {
        if (num_blocks < 2048)
                return -1;
-       if (num_blocks < 32768)
-               return (1024);
-       if (num_blocks < 256*1024)
-               return (4096);
-       if (num_blocks < 512*1024)
-               return (8192);
-       if (num_blocks < 1024*1024)
-               return (16384);
-       return 32768;
+       if (num_blocks < 32768)         /* 128 MB */
+               return (1024);                  /* 4 MB */
+       if (num_blocks < 256*1024)      /* 1 GB */
+               return (4096);                  /* 16 MB */
+       if (num_blocks < 512*1024)      /* 2 GB */
+               return (8192);                  /* 32 MB */
+       if (num_blocks < 4096*1024)     /* 16 GB */
+               return (16384);                 /* 64 MB */
+       if (num_blocks < 8192*1024)     /* 32 GB */
+               return (32768);                 /* 128 MB */
+       if (num_blocks < 16384*1024)    /* 64 GB */
+               return (65536);                 /* 256 MB */
+       if (num_blocks < 32768*1024)    /* 128 GB */
+               return (131072);                /* 512 MB */
+       return 262144;                          /* 1 GB */
 }
 
 int ext2fs_journal_sb_start(int blocksize)

diff --git a/tests/d_dumpe2fs_group_only/expect b/tests/d_dumpe2fs_group_only/expect
index 78f97a2..52610e6 100644 (file)
--- a/tests/d_dumpe2fs_group_only/expect
+++ b/tests/d_dumpe2fs_group_only/expect
@@ -4,7 +4,7 @@ Superblock backups stored on blocks:
 
 Allocating group tables:      \b\b\b\b\bdone                            
 Writing inode tables:      \b\b\b\b\bdone                            
-Creating journal (32768 blocks): done
+Creating journal (16384 blocks): done
 Writing superblocks and filesystem accounting information:      \b\b\b\b\bdone
 
 Pass 1: Checking inodes, blocks, and sizes
@@ -12,7 +12,7 @@ Pass 2: Checking directory structure
 Pass 3: Checking directory connectivity
 Pass 4: Checking reference counts
 Pass 5: Checking group summary information
-test_filesys: 11/262144 files (0.0% non-contiguous), 51278/1048576 blocks
+test_filesys: 11/262144 files (0.0% non-contiguous), 34894/1048576 blocks
 Exit status is 0
 dumpe2fs output
 

diff --git a/tests/t_uninit_bg_rm/expect b/tests/t_uninit_bg_rm/expect
index 61e9eaa..68f8b51 100644 (file)
--- a/tests/t_uninit_bg_rm/expect
+++ b/tests/t_uninit_bg_rm/expect
@@ -7,7 +7,7 @@ Pass 2: Checking directory structure
 Pass 3: Checking directory connectivity
 Pass 4: Checking reference counts
 Pass 5: Checking group summary information
-test_filesys: 11/65536 files (0.0% non-contiguous), 52294/1048576 blocks
+test_filesys: 11/65536 files (0.0% non-contiguous), 35910/1048576 blocks
  
 mke2fs -q -t ext4 -O bigalloc -F -o Linux -b 1024 -C 8192 test.img 10G
 tune2fs -f -O ^uninit_bg test.img
@@ -18,4 +18,4 @@ Pass 2: Checking directory structure
 Pass 3: Checking directory connectivity
 Pass 4: Checking reference counts
 Pass 5: Checking group summary information
-test_filesys: 11/655360 files (0.0% non-contiguous), 199864/10485760 blocks
+test_filesys: 11/655360 files (0.0% non-contiguous), 232632/10485760 blocks