Ted and Darrick,
We're back with a Yocto Project use case. We use mkfs.ext4 to create our
root filesystems. For one of our larger images including an X desktop
and an SDK (toolchain, etc.), it took over 8 minutes to complete.
Richard Purdie noticed most of this time was in ext2fs_new_block2. He
provided this small hack to test an idea and it has reduced the runtime
to 35 seconds. The images function as expected.
Can you have a look and see if there some value in this approach, or if
perhaps it might lead to a more appropriate/correct solution?
Thanks!
Darren
(What follows is the test patch from Richard for the Yocto Project)
The comment to this function says:
"""
* Stupid algorithm --- we now just search forward starting from the
* goal. Should put in a smarter one someday....
"""
This adds in a rather hacky algorthim which starts where we finished
searching previously using a static variable rather than starting
from scratch if a hint isn't provided.
This was after noticing that mkfs.ext4 -F X -d Y was spending *lots*
of time in ext2fs_new_block2 called from ext2fs_bmap from
ext2fs_file_write().
Numbers wise, this took a core-image-sato-sdk mkfs time from over
8 minutes to around 35 seconds.
Upstream-Status: Pending
RP 2015/02/20
Index: e2fsprogs-1.42.9/lib/ext2fs/alloc.c
===================================================================
--- e2fsprogs-1.42.9.orig/lib/ext2fs/alloc.c
+++ e2fsprogs-1.42.9/lib/ext2fs/alloc.c
@@ -160,6 +160,8 @@ errcode_t ext2fs_new_inode(ext2_filsys f
return 0;
}
+static blk64_t last_goal = 0;
+
/*
* Stupid algorithm --- we now just search forward starting from the
* goal. Should put in a smarter one someday....
@@ -170,6 +172,9 @@ errcode_t ext2fs_new_block2(ext2_filsys
blk64_t i;
int c_ratio;
+ if (!goal)
+ goal = last_goal;
+
EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
if (!map)
@@ -194,6 +199,7 @@ errcode_t ext2fs_new_block2(ext2_filsys
if (!ext2fs_fast_test_block_bitmap2(map, i)) {
*ret = i;
+ last_goal = i;
return 0;
}
i = (i + c_ratio) & ~(c_ratio - 1);
--
Darren Hart
Intel Open Source Technology Center
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