Re: [f2fs-dev] [PATCH V2] f2fs: more fast lookup for gc_inode list

[Changman Lee <cm224.lee@samsung.com>]

Hi Yu,

Thanks for your review.

Changes from V3
  o check if entry exists to avoid many kmem_cache_{alloc, free}

Changes from V2
  o rename iradix to iroot
  o declare gc_inode_list in gc.h

 Changes from V1
  o introduce gc_inode_list containing ilist and iradix
  o use local variable
  o call radix_tree_delete before iput
  o retry to add inode into radix_tree
  o call list_del explicitly

--> 8 --
>From 0c2c0d7da997ca90f3101e6195f3ed72fb1940d3 Mon Sep 17 00:00:00 2001
From: Changman Lee <cm224.lee@samsung.com>
Date: Fri, 28 Nov 2014 15:49:40 +0000
Subject: [PATCH] f2fs: more fast lookup for gc_inode list

If there are many inodes that have data blocks in victim segment,
it takes long time to find a inode in gc_inode list.
Let's use radix_tree to reduce lookup time.

Signed-off-by: Changman Lee <cm224.lee@samsung.com>
---
 fs/f2fs/gc.c | 48 +++++++++++++++++++++++++++++-------------------
 fs/f2fs/gc.h |  5 +++++
 2 files changed, 34 insertions(+), 19 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 29fc7e5..75b1d71 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -338,34 +338,42 @@ static const struct victim_selection default_v_ops = {
 	.get_victim = get_victim_by_default,
 };
 
-static struct inode *find_gc_inode(nid_t ino, struct list_head *ilist)
+static struct inode *find_gc_inode(struct gc_inode_list *gc_list, nid_t ino)
 {
 	struct inode_entry *ie;
 
-	list_for_each_entry(ie, ilist, list)
-		if (ie->inode->i_ino == ino)
-			return ie->inode;
+	ie = radix_tree_lookup(&gc_list->iroot, ino);
+	if (ie)
+		return ie->inode;
 	return NULL;
 }
 
-static void add_gc_inode(struct inode *inode, struct list_head *ilist)
+static void add_gc_inode(struct gc_inode_list *gc_list, struct inode *inode)
 {
 	struct inode_entry *new_ie;
+	int ret;
 
-	if (inode == find_gc_inode(inode->i_ino, ilist)) {
+	if (inode == find_gc_inode(gc_list, inode->i_ino)) {
 		iput(inode);
 		return;
 	}
-
+retry:
 	new_ie = f2fs_kmem_cache_alloc(winode_slab, GFP_NOFS);
 	new_ie->inode = inode;
-	list_add_tail(&new_ie->list, ilist);
+
+	ret = radix_tree_insert(&gc_list->iroot, inode->i_ino, new_ie);
+	if (ret) {
+		kmem_cache_free(winode_slab, new_ie);
+		goto retry;
+	}
+	list_add_tail(&new_ie->list, &gc_list->ilist);
 }
 
-static void put_gc_inode(struct list_head *ilist)
+static void put_gc_inode(struct gc_inode_list *gc_list)
 {
 	struct inode_entry *ie, *next_ie;
-	list_for_each_entry_safe(ie, next_ie, ilist, list) {
+	list_for_each_entry_safe(ie, next_ie, &gc_list->ilist, list) {
+		radix_tree_delete(&gc_list->iroot, ie->inode->i_ino);
 		iput(ie->inode);
 		list_del(&ie->list);
 		kmem_cache_free(winode_slab, ie);
@@ -551,7 +559,7 @@ out:
  * the victim data block is ignored.
  */
 static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
-		struct list_head *ilist, unsigned int segno, int gc_type)
+		struct gc_inode_list *gc_list, unsigned int segno, int gc_type)
 {
 	struct super_block *sb = sbi->sb;
 	struct f2fs_summary *entry;
@@ -609,12 +617,12 @@ next_step:
 			}
 
 			f2fs_put_page(data_page, 0);
-			add_gc_inode(inode, ilist);
+			add_gc_inode(gc_list, inode);
 			continue;
 		}
 
 		/* phase 3 */
-		inode = find_gc_inode(dni.ino, ilist);
+		inode = find_gc_inode(gc_list, dni.ino);
 		if (inode) {
 			start_bidx = start_bidx_of_node(nofs,
 							F2FS_I(inode));
@@ -658,7 +666,7 @@ static int __get_victim(struct f2fs_sb_info *sbi, unsigned int *victim,
 }
 
 static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
-				struct list_head *ilist, int gc_type)
+				struct gc_inode_list *gc_list, int gc_type)
 {
 	struct page *sum_page;
 	struct f2fs_summary_block *sum;
@@ -676,7 +684,7 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 		gc_node_segment(sbi, sum->entries, segno, gc_type);
 		break;
 	case SUM_TYPE_DATA:
-		gc_data_segment(sbi, sum->entries, ilist, segno, gc_type);
+		gc_data_segment(sbi, sum->entries, gc_list, segno, gc_type);
 		break;
 	}
 	blk_finish_plug(&plug);
@@ -689,16 +697,18 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 
 int f2fs_gc(struct f2fs_sb_info *sbi)
 {
-	struct list_head ilist;
 	unsigned int segno, i;
 	int gc_type = BG_GC;
 	int nfree = 0;
 	int ret = -1;
 	struct cp_control cpc;
+	struct gc_inode_list gc_list = {
+		.ilist = LIST_HEAD_INIT(gc_list.ilist),
+		.iroot = RADIX_TREE_INIT(GFP_ATOMIC),
+	};
 
 	cpc.reason = test_opt(sbi, FASTBOOT) ? CP_UMOUNT : CP_SYNC;
 
-	INIT_LIST_HEAD(&ilist);
 gc_more:
 	if (unlikely(!(sbi->sb->s_flags & MS_ACTIVE)))
 		goto stop;
@@ -720,7 +730,7 @@ gc_more:
 								META_SSA);
 
 	for (i = 0; i < sbi->segs_per_sec; i++)
-		do_garbage_collect(sbi, segno + i, &ilist, gc_type);
+		do_garbage_collect(sbi, segno + i, &gc_list, gc_type);
 
 	if (gc_type == FG_GC) {
 		sbi->cur_victim_sec = NULL_SEGNO;
@@ -736,7 +746,7 @@ gc_more:
 stop:
 	mutex_unlock(&sbi->gc_mutex);
 
-	put_gc_inode(&ilist);
+	put_gc_inode(&gc_list);
 	return ret;
 }
 
diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
index 16f0b2b..6ff7ad3 100644
--- a/fs/f2fs/gc.h
+++ b/fs/f2fs/gc.h
@@ -40,6 +40,11 @@ struct inode_entry {
 	struct inode *inode;
 };
 
+struct gc_inode_list {
+	struct list_head ilist;
+	struct radix_tree_root iroot;
+};
+
 /*
  * inline functions
  */
-- 
1.9.1