Re: [f2fs-dev] [PATCH 2/3] f2fs crypto: use bounce pages from mempool first

[Jaegeuk Kim]

Hi Chao,

On Mon, May 25, 2015 at 06:00:47PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk@xxxxxxxxxx]
> > Sent: Friday, May 22, 2015 8:40 AM
> > To: linux-kernel@xxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx;
> > linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
> > Cc: Jaegeuk Kim
> > Subject: [f2fs-dev] [PATCH 2/3] f2fs crypto: use bounce pages from mempool first
> > 
> > If a lot of write streams are triggered, alloc_page and __free_page are
> > costly called, resulting in high memory pressure.
> > 
> > In order to avoid that, let's reuse mempool pages for writeback pages.
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > ---
> >  fs/f2fs/crypto.c | 16 ++++------------
> >  1 file changed, 4 insertions(+), 12 deletions(-)
> > 
> > diff --git a/fs/f2fs/crypto.c b/fs/f2fs/crypto.c
> > index 2c7819a..2ceee68 100644
> > --- a/fs/f2fs/crypto.c
> > +++ b/fs/f2fs/crypto.c
> > @@ -408,20 +408,12 @@ struct page *f2fs_encrypt(struct inode *inode,
> >  		return (struct page *)ctx;
> > 
> >  	/* The encryption operation will require a bounce page. */
> > -	ciphertext_page = alloc_page(GFP_NOFS);
> > +	ciphertext_page = mempool_alloc(f2fs_bounce_page_pool, GFP_NOFS);
> >  	if (!ciphertext_page) {
> > -		/*
> > -		 * This is a potential bottleneck, but at least we'll have
> > -		 * forward progress.
> > -		 */
> > -		ciphertext_page = mempool_alloc(f2fs_bounce_page_pool,
> > -							GFP_NOFS);
> > -		if (WARN_ON_ONCE(!ciphertext_page))
> > -			ciphertext_page = mempool_alloc(f2fs_bounce_page_pool,
> > -						GFP_NOFS | __GFP_WAIT);
> > -		ctx->flags &= ~F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
> > -	} else {
> > +		ciphertext_page = alloc_page(GFP_NOFS);
> 
> Using alloc_page(GFP_NOFS | __GFP_WAIT) to avoid failure?

#define GFP_NOFS	(__GFP_WAIT | __GFP_IO)

Thanks,

> 
> Thanks,
> 
> >  		ctx->flags |= F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
> > +	} else {
> > +		ctx->flags &= ~F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
> >  	}
> >  	ctx->flags |= F2FS_WRITE_PATH_FL;
> >  	ctx->w.bounce_page = ciphertext_page;
> > --
> > 2.1.1
> > 
> > 
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