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* [PATCH v2] Btrfs: add skeleton code for compression heuristic
@ 2017-07-14 12:00 Timofey Titovets
  2017-07-14 12:24 ` David Sterba
  0 siblings, 1 reply; 2+ messages in thread
From: Timofey Titovets @ 2017-07-14 12:00 UTC (permalink / raw)
  To: linux-btrfs; +Cc: Timofey Titovets

For now that code just return true
Later more complex heuristic code will be added

Changes v1 -> v2:
 - Heuristic call moved into inode_need_compress() function

Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
---
 fs/btrfs/compression.c | 22 ++++++++++++++++++++++
 fs/btrfs/compression.h |  2 ++
 fs/btrfs/inode.c       | 18 ++++++++++++------
 3 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 2c0b7b57fcd5..d0cf2024def7 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1046,3 +1046,25 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
 
 	return 1;
 }
+
+/*
+ * Heuristic skeleton
+ * For now just would be a naive and very optimistic 'return true'.
+ */
+int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end)
+{
+	u64 index = start >> PAGE_SHIFT;
+	u64 end_index = end >> PAGE_SHIFT;
+	struct page *page;
+	int ret = 1;
+
+	while (index <= end_index) {
+		page = find_get_page(inode->i_mapping, index);
+		kmap(page);
+		kunmap(page);
+		put_page(page);
+		index++;
+	}
+
+	return ret;
+}
diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index 87f6d3332163..8508ba6b9aef 100644
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -129,4 +129,6 @@ struct btrfs_compress_op {
 extern const struct btrfs_compress_op btrfs_zlib_compress;
 extern const struct btrfs_compress_op btrfs_lzo_compress;
 
+int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end);
+
 #endif
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 06dea7c89bbd..27922b29fa4e 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -392,20 +392,26 @@ static noinline int add_async_extent(struct async_cow *cow,
 	return 0;
 }
 
-static inline int inode_need_compress(struct inode *inode)
+static inline int inode_need_compress(struct inode *inode, u64 start, u64 end)
 {
+	int ret = 0;
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 
 	/* force compress */
 	if (btrfs_test_opt(fs_info, FORCE_COMPRESS))
-		return 1;
+		goto try_compress;
 	/* bad compression ratios */
 	if (BTRFS_I(inode)->flags & BTRFS_INODE_NOCOMPRESS)
-		return 0;
+		goto skip_compress;
 	if (btrfs_test_opt(fs_info, COMPRESS) ||
 	    BTRFS_I(inode)->flags & BTRFS_INODE_COMPRESS ||
 	    BTRFS_I(inode)->force_compress)
-		return 1;
+		goto try_compress;
+	goto skip_compress;
+try_compress:
+	ret = btrfs_compress_heuristic(inode, start, end);
+	return ret;
+skip_compress:
 	return 0;
 }
 
@@ -503,7 +509,7 @@ static noinline void compress_file_range(struct inode *inode,
 	 * inode has not been flagged as nocompress.  This flag can
 	 * change at any time if we discover bad compression ratios.
 	 */
-	if (inode_need_compress(inode)) {
+	if (inode_need_compress(inode, start, end)) {
 		WARN_ON(pages);
 		pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
 		if (!pages) {
@@ -1576,7 +1582,7 @@ static int run_delalloc_range(void *private_data, struct page *locked_page,
 	} else if (BTRFS_I(inode)->flags & BTRFS_INODE_PREALLOC && !force_cow) {
 		ret = run_delalloc_nocow(inode, locked_page, start, end,
 					 page_started, 0, nr_written);
-	} else if (!inode_need_compress(inode)) {
+	} else if (!inode_need_compress(inode, start, end)) {
 		ret = cow_file_range(inode, locked_page, start, end, end,
 				      page_started, nr_written, 1, NULL);
 	} else {
-- 
2.13.2


^ permalink raw reply related	[flat|nested] 2+ messages in thread
* Re: [PATCH v2] Btrfs: add skeleton code for compression heuristic
  2017-07-14 12:00 [PATCH v2] Btrfs: add skeleton code for compression heuristic Timofey Titovets
@ 2017-07-14 12:24 ` David Sterba
  0 siblings, 0 replies; 2+ messages in thread
From: David Sterba @ 2017-07-14 12:24 UTC (permalink / raw)
  To: Timofey Titovets; +Cc: linux-btrfs

On Fri, Jul 14, 2017 at 03:00:46PM +0300, Timofey Titovets wrote:
> For now that code just return true
> Later more complex heuristic code will be added
> 
> Changes v1 -> v2:
>  - Heuristic call moved into inode_need_compress() function
> 
> Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
> ---
>  fs/btrfs/compression.c | 22 ++++++++++++++++++++++
>  fs/btrfs/compression.h |  2 ++
>  fs/btrfs/inode.c       | 18 ++++++++++++------
>  3 files changed, 36 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index 2c0b7b57fcd5..d0cf2024def7 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -1046,3 +1046,25 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
>  
>  	return 1;
>  }
> +
> +/*
> + * Heuristic skeleton
> + * For now just would be a naive and very optimistic 'return true'.
> + */
> +int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end)
> +{
> +	u64 index = start >> PAGE_SHIFT;
> +	u64 end_index = end >> PAGE_SHIFT;
> +	struct page *page;
> +	int ret = 1;
> +
> +	while (index <= end_index) {
> +		page = find_get_page(inode->i_mapping, index);
> +		kmap(page);
> +		kunmap(page);
> +		put_page(page);
> +		index++;
> +	}
> +
> +	return ret;
> +}
> diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
> index 87f6d3332163..8508ba6b9aef 100644
> --- a/fs/btrfs/compression.h
> +++ b/fs/btrfs/compression.h
> @@ -129,4 +129,6 @@ struct btrfs_compress_op {
>  extern const struct btrfs_compress_op btrfs_zlib_compress;
>  extern const struct btrfs_compress_op btrfs_lzo_compress;
>  
> +int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end);
> +
>  #endif
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 06dea7c89bbd..27922b29fa4e 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -392,20 +392,26 @@ static noinline int add_async_extent(struct async_cow *cow,
>  	return 0;
>  }
>  
> -static inline int inode_need_compress(struct inode *inode)
> +static inline int inode_need_compress(struct inode *inode, u64 start, u64 end)
>  {
> +	int ret = 0;
>  	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
>  
>  	/* force compress */
>  	if (btrfs_test_opt(fs_info, FORCE_COMPRESS))
> -		return 1;
> +		goto try_compress;
>  	/* bad compression ratios */
>  	if (BTRFS_I(inode)->flags & BTRFS_INODE_NOCOMPRESS)
> -		return 0;
> +		goto skip_compress;
>  	if (btrfs_test_opt(fs_info, COMPRESS) ||
>  	    BTRFS_I(inode)->flags & BTRFS_INODE_COMPRESS ||
>  	    BTRFS_I(inode)->force_compress)
> -		return 1;
> +		goto try_compress;
> +	goto skip_compress;
> +try_compress:
> +	ret = btrfs_compress_heuristic(inode, start, end);
> +	return ret;
> +skip_compress:
>  	return 0;

That's a bit wilde goto skip_compress can be simple return 0. Also you
can drop ret and return btrfs_compress_heuristic(...);

Otherwise it looks ok, just the documentation side could be improved,
like describe the purpose and expected furure enhancements.

>  }
>  
> @@ -503,7 +509,7 @@ static noinline void compress_file_range(struct inode *inode,
>  	 * inode has not been flagged as nocompress.  This flag can
>  	 * change at any time if we discover bad compression ratios.
>  	 */
> -	if (inode_need_compress(inode)) {
> +	if (inode_need_compress(inode, start, end)) {
>  		WARN_ON(pages);
>  		pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
>  		if (!pages) {
> @@ -1576,7 +1582,7 @@ static int run_delalloc_range(void *private_data, struct page *locked_page,
>  	} else if (BTRFS_I(inode)->flags & BTRFS_INODE_PREALLOC && !force_cow) {
>  		ret = run_delalloc_nocow(inode, locked_page, start, end,
>  					 page_started, 0, nr_written);
> -	} else if (!inode_need_compress(inode)) {
> +	} else if (!inode_need_compress(inode, start, end)) {
>  		ret = cow_file_range(inode, locked_page, start, end, end,
>  				      page_started, nr_written, 1, NULL);
>  	} else {
> -- 
> 2.13.2
> 
> --
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2017-07-14 12:00 [PATCH v2] Btrfs: add skeleton code for compression heuristic Timofey Titovets
2017-07-14 12:24 ` David Sterba

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