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Date:   Thu, 3 Jun 2021 09:13:53 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     Chao Yu <yuchao0@huawei.com>, linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v6] f2fs: compress: add compress_inode to
 cache compressed blocks
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On 06/03, Chao Yu wrote:
> On 2021/6/2 23:34, Jaegeuk Kim wrote:
> > On 06/02, Chao Yu wrote:
> > > On 2021/6/2 1:27, Jaegeuk Kim wrote:
> > > > On 06/01, Jaegeuk Kim wrote:
> > > > > On 05/26, Chao Yu wrote:
> > > > > > On 2021/5/26 21:26, Jaegeuk Kim wrote:
> > > > > > > On 05/26, Chao Yu wrote:
> > > > > > > > On 2021/5/25 22:01, Jaegeuk Kim wrote:
> > > > > > > > > On 05/25, Chao Yu wrote:
> > > > > > > > > > On 2021/5/25 21:02, Jaegeuk Kim wrote:
> > > > > > > > > > > On 05/25, Jaegeuk Kim wrote:
> > > > > > > > > > > > On 05/25, Chao Yu wrote:
> > > > > > > > > > > > > Also, and queue this?
> > > > > > > > > > > > 
> > > > > > > > > > > > Easy to get this?
> > > > > > > > > > > 
> > > > > > > > > > > need GFP_NOFS?
> > > > > > > > > > 
> > > > > > > > > > Not sure, I use __GFP_IO intentionally here to avoid __GFP_RECLAIM from
> > > > > > > > > > GFP_NOFS, because in low memory case, I don't want to instead page cache
> > > > > > > > > > of normal file with page cache of sbi->compress_inode.
> > > > > > > > > > 
> > > > > > > > > > What is memory size in your vm?
> > > > > > > > > 
> > > > > > > > > 4GB. If I set GFP_NOFS, I don't see the error anymore, at least.
> > > > > > > > 
> > > > > > > > I applied below patch and don't see the warning message anymore.
> > > > > > > > 
> > > > > > > > ---
> > > > > > > >     fs/f2fs/compress.c | 2 +-
> > > > > > > >     1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > > > > 
> > > > > > > > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> > > > > > > > index 701dd0f6f4ec..ed5b7fabc604 100644
> > > > > > > > --- a/fs/f2fs/compress.c
> > > > > > > > +++ b/fs/f2fs/compress.c
> > > > > > > > @@ -1703,7 +1703,7 @@ void f2fs_cache_compressed_page(struct f2fs_sb_info *sbi, struct page *page,
> > > > > > > >     	avail_ram = si.totalram - si.totalhigh;
> > > > > > > > 
> > > > > > > >     	/* free memory is lower than watermark, deny caching compress page */
> > > > > > > > -	if (free_ram <= sbi->compress_watermark / 100 * avail_ram)
> > > > > > 
> > > > > > This is buggy, because sbi->compress_watermark equals to 20, so that
> > > > > > sbi->compress_watermark / 100 * avail_ram always be zero...
> > > > > > 
> > > > > > After this change, if free ram is lower, we may just skip caching
> > > > > > compressed blocks here.
> > > > > 
> > > > > Can we move this in f2fs_available_free_memory()?
> > > 
> > > More clean.
> > > 
> > > One comment below:
> > > 
> > > > 
> > > > Testing this.
> > > > 
> > > > ---
> > > >    fs/f2fs/compress.c | 14 +-------------
> > > >    fs/f2fs/node.c     | 11 ++++++++++-
> > > >    fs/f2fs/node.h     |  1 +
> > > >    3 files changed, 12 insertions(+), 14 deletions(-)
> > > > 
> > > > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> > > > index 9fd62a0a646b..455561826c7d 100644
> > > > --- a/fs/f2fs/compress.c
> > > > +++ b/fs/f2fs/compress.c
> > > > @@ -1688,8 +1688,6 @@ void f2fs_cache_compressed_page(struct f2fs_sb_info *sbi, struct page *page,
> > > >    {
> > > >    	struct page *cpage;
> > > >    	int ret;
> > > > -	struct sysinfo si;
> > > > -	unsigned long free_ram, avail_ram;
> > > >    	if (!test_opt(sbi, COMPRESS_CACHE))
> > > >    		return;
> > > > @@ -1697,17 +1695,7 @@ void f2fs_cache_compressed_page(struct f2fs_sb_info *sbi, struct page *page,
> > > >    	if (!f2fs_is_valid_blkaddr(sbi, blkaddr, DATA_GENERIC_ENHANCE_READ))
> > > >    		return;
> > > > -	si_meminfo(&si);
> > > > -	free_ram = si.freeram;
> > > > -	avail_ram = si.totalram - si.totalhigh;
> > > > -
> > > > -	/* free memory is lower than watermark, deny caching compress page */
> > > > -	if (free_ram <= sbi->compress_watermark / 100 * avail_ram)
> > > > -		return;
> > > > -
> > > > -	/* cached page count exceed threshold, deny caching compress page */
> > > > -	if (COMPRESS_MAPPING(sbi)->nrpages >=
> > > 
> > > Need to cover COMPRESS_MAPPING() with CONFIG_F2FS_FS_COMPRESSION.
> > 
> > Added like this.
> > 
> > --- a/fs/f2fs/node.c
> > +++ b/fs/f2fs/node.c
> > @@ -99,6 +99,7 @@ bool f2fs_available_free_memory(struct f2fs_sb_info *sbi, int type)
> >                                  sizeof(struct discard_cmd)) >> PAGE_SHIFT;
> >                  res = mem_size < (avail_ram * nm_i->ram_thresh / 100);
> >          } else if (type == COMPRESS_PAGE) {
> > +#ifdef CONFIG_F2FS_FS_COMPRESSION
> 
> How about adding free_ram definition and assigment here?
> 
> unsigned long free_ram = val.freeram;

Done.

> 
> Thanks,
> 
> >                  /*
> >                   * free memory is lower than watermark or cached page count
> >                   * exceed threshold, deny caching compress page.
> > @@ -106,6 +107,9 @@ bool f2fs_available_free_memory(struct f2fs_sb_info *sbi, int type)
> >                  res = (free_ram > avail_ram * sbi->compress_watermark / 100) &&
> >                          (COMPRESS_MAPPING(sbi)->nrpages <
> >                           free_ram * sbi->compress_percent / 100);
> > +#else
> > +               res = false;
> > +#endif
> >          } else {
> >                  if (!sbi->sb->s_bdi->wb.dirty_exceeded)
> >                          return true;
> > 
> > > 
> > > Thanks,
> > > 
> > > > -			free_ram / 100 * sbi->compress_percent)
> > > > +	if (!f2fs_available_free_memory(sbi, COMPRESS_PAGE))
> > > >    		return;
> > > >    	cpage = find_get_page(COMPRESS_MAPPING(sbi), blkaddr);
> > > > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> > > > index 3a8f7afa5059..67093416ce9c 100644
> > > > --- a/fs/f2fs/node.c
> > > > +++ b/fs/f2fs/node.c
> > > > @@ -45,7 +45,7 @@ bool f2fs_available_free_memory(struct f2fs_sb_info *sbi, int type)
> > > >    	struct f2fs_nm_info *nm_i = NM_I(sbi);
> > > >    	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> > > >    	struct sysinfo val;
> > > > -	unsigned long avail_ram;
> > > > +	unsigned long avail_ram, free_ram;
> > > >    	unsigned long mem_size = 0;
> > > >    	bool res = false;
> > > > @@ -56,6 +56,7 @@ bool f2fs_available_free_memory(struct f2fs_sb_info *sbi, int type)
> > > >    	/* only uses low memory */
> > > >    	avail_ram = val.totalram - val.totalhigh;
> > > > +	free_ram = val.freeram;
> > > >    	/*
> > > >    	 * give 25%, 25%, 50%, 50%, 50% memory for each components respectively
> > > > @@ -97,6 +98,14 @@ bool f2fs_available_free_memory(struct f2fs_sb_info *sbi, int type)
> > > >    		mem_size = (atomic_read(&dcc->discard_cmd_cnt) *
> > > >    				sizeof(struct discard_cmd)) >> PAGE_SHIFT;
> > > >    		res = mem_size < (avail_ram * nm_i->ram_thresh / 100);
> > > > +	} else if (type == COMPRESS_PAGE) {
> > > > +		/*
> > > > +		 * free memory is lower than watermark or cached page count
> > > > +		 * exceed threshold, deny caching compress page.
> > > > +		 */
> > > > +		res = (free_ram > avail_ram * sbi->compress_watermark / 100) &&
> > > > +			(COMPRESS_MAPPING(sbi)->nrpages <
> > > > +			 free_ram * sbi->compress_percent / 100);
> > > >    	} else {
> > > >    		if (!sbi->sb->s_bdi->wb.dirty_exceeded)
> > > >    			return true;
> > > > diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
> > > > index d85e8659cfda..84d45385d1f2 100644
> > > > --- a/fs/f2fs/node.h
> > > > +++ b/fs/f2fs/node.h
> > > > @@ -148,6 +148,7 @@ enum mem_type {
> > > >    	EXTENT_CACHE,	/* indicates extent cache */
> > > >    	INMEM_PAGES,	/* indicates inmemory pages */
> > > >    	DISCARD_CACHE,	/* indicates memory of cached discard cmds */
> > > > +	COMPRESS_PAGE,	/* indicates memory of cached compressed pages */
> > > >    	BASE_CHECK,	/* check kernel status */
> > > >    };
> > > >