Re: [f2fs-dev] f2fs compress performance problem

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 06/04, changfengnan@vivo.com wrote:
> Hi:
> 
> I've been working on f2fs compression for a while, I'm confused on f2fs
> compression performance, after a while reserch, 
> I found some problem, maybe need some discuss.
> I use AndroBench test performance on mobile, after enable compression, the
> benchmark scores have dropped a lot.
> Specifically:
> 1. 32M sequential read has dropped to 50% of original. Test case open file
> with O_RDONLY|O_DIRECT, and set POSIX_FADV_RANDOM, the major resaon 
> is disable readahed. For now,I didn't found any patch can improve this. 
> 2. 4K random read has dropped to 40% of original, after merge `f2fs:
> compress: add compress_inode to cache compressed blocks`,
> significant improvement in random read performance, up to 90% of original,
> maybe more.
> 3. 32M sequential overwrite has dropped to 10% of original, after merge
> `f2fs: compress: remove unneeded read when rewrite whole cluster`
> up to 30% of original.
> 4. 4K random read has dropped to 1% of original, yes only 1% of original, I
> found  open file with O_WRONLY|O_DSYNC|O_DIRECT is  an important reason, 
> every time sync a compress inode need do checkpoint, after I remove
> checkpoint on compress inode, up to 10% of original. And I think major
> reason of this
> is we need read whole cluster and rewrite it ,but I did't think of any
> method to improve this.
> 
> I want to know is there any idea can help to improve this.
> And I want to know do we have goal for the performance of compression, is it
> possible to achieve the original performance?

Could you please check compress_cache and extent_cache that can improve read
performance? Both were done quite recently.

> 
> Thanks.


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