e2fsck: make default smallest RA size to 1M

If we have a smaller inodes per group, default ra size could
be very small(etc 128KiB), this hurts performances.

Tune above 128K to 1M, i see pass1 time drop down from
677.12 seconds to 246 secons with 32 threads.

E2fsprogs-commit: 9226b3264b74044013f4933280b1989c33be42f3

Change-Id: Ia503b4f73dc8f3d5e6be705c7311bdacc5b874a9
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/e2fsck/readahead.c b/e2fsck/readahead.c
index 38d4ec4..40b7366 100644 (file)
--- a/e2fsck/readahead.c
+++ b/e2fsck/readahead.c
@@ -234,6 +234,8 @@ int e2fsck_can_readahead(ext2_filsys fs)
        return err != EXT2_ET_OP_NOT_SUPPORTED;
 }
 
+#define MIN_DEFAULT_RA (1024 * 1024)
+
 unsigned long long e2fsck_guess_readahead(ext2_filsys fs)
 {
        unsigned long long guess;
@@ -245,6 +247,8 @@ unsigned long long e2fsck_guess_readahead(ext2_filsys fs)
         * in e2fsck runtime.
         */
        guess = 2ULL * fs->blocksize * fs->inode_blocks_per_group;
+       if (guess < MIN_DEFAULT_RA)
+               guess = MIN_DEFAULT_RA;
 
        /* Disable RA if it'd use more 1/50th of RAM. */
        if (get_memory_size() > (guess * 50))