linux-kernel - Re: [PATCH] erofs: enable large folio in device-based mode

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Date:   Fri, 11 Nov 2022 14:36:25 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     JeffleXu <jefflexu@...ux.alibaba.com>
Cc:     xiang@...nel.org, chao@...nel.org, linux-erofs@...ts.ozlabs.org,
        huyue2@...lpad.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] erofs: enable large folio in device-based mode

Hi,

On Thu, Nov 10, 2022 at 03:59:14PM +0800, JeffleXu wrote:
> 
> 
> On 11/10/22 3:40 PM, Jingbo Xu wrote:
> > Enable large folio in device-based mode. Then the radahead routine will
> > pass down large folio containing multiple pages.
> > 
> > Enable this feature for non-compressed format for now, until the
> > compression part supports large folio later.
> > 
> > Signed-off-by: Jingbo Xu <jefflexu@...ux.alibaba.com>
> > ---
> > I have tested it under workload of Linux compiling. I know it's not a
> > perfect workload testing this feature, because large folio is less
> > likely hit in this case since source files are generally small. But I
> > indeed observed large folios (e.g. 16 pages) by peeking
> > readahead_count(rac) in erofs_readahead().
> 
> Sorry, readahead_count(rac) returns the whole number of pages inside the
> rac, which can not prove large folio passed in.
> 
> I retired later and observed large folio (e.g. with order 2) by peeking
> folio_order(ctx->cur_folio) inside iomap_readahead_iter()

I will test it as well after I send out all bug fixes for this cycle.

Thanks,
Gao Xiang

> 
> > ---
> >  fs/erofs/inode.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
> > index ad2a82f2eb4c..e457b8a59ee7 100644
> > --- a/fs/erofs/inode.c
> > +++ b/fs/erofs/inode.c
> > @@ -295,6 +295,8 @@ static int erofs_fill_inode(struct inode *inode)
> >  		goto out_unlock;
> >  	}
> >  	inode->i_mapping->a_ops = &erofs_raw_access_aops;
> > +	if (!erofs_is_fscache_mode(inode->i_sb))
> > +		mapping_set_large_folios(inode->i_mapping);
> >  #ifdef CONFIG_EROFS_FS_ONDEMAND
> >  	if (erofs_is_fscache_mode(inode->i_sb))
> >  		inode->i_mapping->a_ops = &erofs_fscache_access_aops;
> 
> -- 
> Thanks,
> Jingbo