linux-kernel - Re: [f2fs-dev] [PATCH v6] f2fs: compress: add compress

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Message-ID: <09fa74d3-a9df-028f-3ebc-2b845e5cd609@kernel.org>
Date:   Wed, 2 Jun 2021 19:49:59 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     Chao Yu <yuchao0@...wei.com>, linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v6] f2fs: compress: add compress_inode to cache
 compressed blocks

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.

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 */
>   };
>   
>