Re: 48 bit ext3 testing

Mingming Cao wrote:
> 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.
>
>   
I ran tiobench with this fix, mounted with extents, and did not get any 
regression.  Looks like the missing reservation window initialization 
was the problem

Thanks!
Avantika
> ---
>
>  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);
>
> _
>
>
>   
---
Avantika Mathur
IBM Linux Technology Center
503-578-3484
[email protected]


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