Re: 48 bit ext3 testing

On Tue, 2006-07-18 at 11:09 -0700, Avantika Mathur LTC wrote:
> Hi,
> 
> I have been testing the performance of the 48 bit patch set.
> As I had mentioned in an earlier ext3 interlock call, I've seen major 
> regression on tiobench for random and sequential writes.  The regression 
> occurs when mounting with extents, for greater than 1 thread.  These 
> results are on both an x86 and ppc64 machines.


The regression seems related to file fragmentation, which makes me
suspect that reservation feature is not turn on. I think I find why:
preciously the reservation window structure is statistically declared in
the in-core ext3 inode itself. Then later we changed it to dynamically:
allocating memory for reservation window only when the first time an
inode needs new blocks.

For the extent block allocation interface: ext3_ext_get_blocks(), we
seems missing this reservation window strucutre initialzation, thus why
reservation is not being turned on and result in file fragmentation.

Attached is a trival fix.

---

 linux-2.6.17-git13-ming/fs/ext3/extents.c |    6 ++++++
 1 files changed, 6 insertions(+)

diff -puN fs/ext3/extents.c~ext3-extent-init-rsv-window fs/ext3/extents.c
--- linux-2.6.17-git13/fs/ext3/extents.c~ext3-extent-init-rsv-window	2006-07-27 19:55:59.586566092 -0700
+++ linux-2.6.17-git13-ming/fs/ext3/extents.c	2006-07-27 20:07:33.370303760 -0700
@@ -1931,6 +1931,12 @@ int ext3_ext_get_blocks(handle_t *handle
 		ext3_ext_put_gap_in_cache(inode, path, iblock);
 		goto out2;
 	}
+	/*
+         * Okay, we need to do block allocation.  Lazily initialize the block
+         * allocation info here if necessary
+        */
+	if (S_ISREG(inode->i_mode) && (!EXT3_I(inode)->i_block_alloc_info))
+		ext3_init_block_alloc_info(inode);
 
 	/* allocate new block */
 	goal = ext3_ext_find_goal(inode, path, iblock);

_



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