Re: Poor creat/delete files performance

[Miao Xie <miaox@cn.fujitsu.com>]

On Wed, 18 Aug 2010 08:09:41 -0400, Chris Mason wrote:
>> We did some performance test and found the create/delete files performance
>> of btrfs is very poor.
>>
>> The test is that we create 50000 files and measure the file-create time
>> first, and then delete these 50000 files and measure the file-delete time.
>> (The attached file is the reproduce program)
>>
>> The result is following:
>> (Unit: second)
>>    Create file performance
>> 		BtrFS		Ext4
>>    Total times:	2.462625	1.449550
>>    Average:	0.000049	0.000029
>>
>>    Delete file performance
>> 		BtrFS		Ext4
>>    Total times:	3.312796	0.997946
>>    Average:	0.000066	0.000020
>>
>> The results were measured on a x86_64 server with 4 cores and 2 SAS disks.
>> By debuging, we found the btrfs spent a lot of time on searching and
>> inserting/removing items in the ctree.
>>
>> Is anyone looking at this issue?
>
> I'm looking at it now, which kernel were you on?  We do spend some CPU
> time on the btree but it shouldn't be a big bottleneck compared to the
> disk.

I tested it on v2.6.35 kernel.

Regards
Miao Xie

>
> This should be very similar to the performance regression that Steve
> Pratt hit.  Our deletion time has always been slower than ext4, but the
> creation time should be the same or faster.
>
> -chris
>
>
>