Re: [f2fs-dev] f2fs compress performance problem

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 07/02, Fengnan Chang wrote:
> Yes, I had enable compress_cache and extent_cache, compress_cache indeed can
> improve random read performance, but couldn't improve other test case.And
> extent_cache was default enabled in my test.

Sorry, we enabled extent_cache for RO partition only.

static inline bool f2fs_may_extent_tree(struct inode *inode)
{
	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);

	if (!test_opt(sbi, EXTENT_CACHE) ||
			is_inode_flag_set(inode, FI_NO_EXTENT) ||
			(is_inode_flag_set(inode, FI_COMPRESSED_FILE) &&
			 !f2fs_sb_has_readonly(sbi)))
		return false;
...


> 
> 
> Fix the description of the previous email:
>  4. 4K random overwrite 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. If I set write size
> equal to cluster size,  it can up to 35% of original. And I think major
> reason of this is we need read whole cluster and rewrite it , I've been
> trying to get around this restriction recently, but haven't made any
> progress yet.
> 
> Thanks.
> 
> On 2021/7/2 1:06, Jaegeuk Kim wrote:
> > 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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