f2fs: throttle the memory footprint with a sysfs entry

This patch introduces ram_thresh, a sysfs entry, which controls the memory
footprint used by the free nid list and the nat cache.

Previously, the free nid list was controlled by MAX_FREE_NIDS, while the nat
cache was managed by NM_WOUT_THRESHOLD.
However, this approach cannot be applied dynamically according to the system.

So, this patch adds ram_thresh that users can specify the threshold, which is
in order of 1 / 1024.
For example, if the total ram size is 4GB and the value is set to 10 by default,
f2fs tries to control the number of free nids and nat caches not to consume over
10 * (4GB / 1024) = 10MB.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
index ee6d28684ee8..c97215432100 100644
--- a/fs/f2fs/node.h
+++ b/fs/f2fs/node.h
@@ -17,15 +17,15 @@
 /* # of pages to perform readahead before building free nids */
 #define FREE_NID_PAGES 4
 
-/* maximum # of free node ids to produce during build_free_nids */
-#define MAX_FREE_NIDS (NAT_ENTRY_PER_BLOCK * FREE_NID_PAGES)
-
 /* maximum readahead size for node during getting data blocks */
 #define MAX_RA_NODE		128
 
 /* maximum cached nat entries to manage memory footprint */
 #define NM_WOUT_THRESHOLD	(64 * NAT_ENTRY_PER_BLOCK)
 
+/* control the memory footprint threshold (10MB per 1GB ram) */
+#define DEF_RAM_THRESHOLD	10
+
 /* vector size for gang look-up from nat cache that consists of radix tree */
 #define NATVEC_SIZE	64
 
@@ -77,6 +77,11 @@ static inline void node_info_from_raw_nat(struct node_info *ni,
 	ni->version = raw_ne->version;
 }
 
+enum nid_type {
+	FREE_NIDS,	/* indicates the free nid list */
+	NAT_ENTRIES	/* indicates the cached nat entry */
+};
+
 /*
  * For free nid mangement
  */