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Date: Thu, 14 Aug 2008 23:14:40 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: cmm@...ibm.com, tytso@....edu, sandeen@...hat.com
Cc: linux-ext4@...r.kernel.org,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH] ext4: Fix small file fragmentation
mballoc small file block allocation use per cpu prealloc
space. Use goal block when searching for the right prealloc
space. Also make sure ext4_da_writepages tries to write
all the pages for small files in single attempt
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
fs/ext4/inode.c | 21 +++++++++++++++------
fs/ext4/mballoc.c | 44 +++++++++++++++++++++++++++++++++++++-------
fs/inode.c | 1 +
3 files changed, 53 insertions(+), 13 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index e144896..0b34998 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2318,13 +2318,12 @@ static int ext4_writepages_trans_blocks(struct inode *inode)
static int ext4_da_writepages(struct address_space *mapping,
struct writeback_control *wbc)
{
- struct inode *inode = mapping->host;
handle_t *handle = NULL;
- int needed_blocks;
- int ret = 0;
- long to_write;
loff_t range_start = 0;
- long pages_skipped = 0;
+ struct inode *inode = mapping->host;
+ int needed_blocks, ret = 0, nr_to_writebump = 0;
+ long to_write, pages_skipped = 0;
+ struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
/*
* No pages to write? This is mainly a kludge to avoid starting
@@ -2333,6 +2332,16 @@ static int ext4_da_writepages(struct address_space *mapping,
*/
if (!mapping->nrpages || !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
return 0;
+ /*
+ * Make sure nr_to_write is >= sbi->s_mb_stream_request
+ * This make sure small files blocks are allocated in
+ * single attempt. This ensure that small files
+ * get less fragmented.
+ */
+ if (wbc->nr_to_write < sbi->s_mb_stream_request) {
+ nr_to_writebump = sbi->s_mb_stream_request - wbc->nr_to_write;
+ wbc->nr_to_write = sbi->s_mb_stream_request;
+ }
if (!wbc->range_cyclic)
/*
@@ -2413,7 +2422,7 @@ static int ext4_da_writepages(struct address_space *mapping,
}
out_writepages:
- wbc->nr_to_write = to_write;
+ wbc->nr_to_write = to_write - nr_to_writebump;
wbc->range_start = range_start;
return ret;
}
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index b14a7c7..1afcb11 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3286,6 +3286,29 @@ static void ext4_mb_use_group_pa(struct ext4_allocation_context *ac,
mb_debug("use %u/%u from group pa %p\n", pa->pa_lstart-len, len, pa);
}
+static struct ext4_prealloc_space *
+ext4_mb_check_group_pa(ext4_fsblk_t goal_block,
+ struct ext4_prealloc_space *pa,
+ struct ext4_prealloc_space *cpa)
+{
+ ext4_fsblk_t cur_distance, new_distance;
+
+ if (cpa == NULL) {
+ atomic_inc(&pa->pa_count);
+ return pa;
+ }
+ cur_distance = abs(goal_block - cpa->pa_pstart);
+ new_distance = abs(goal_block - pa->pa_pstart);
+
+ if (cur_distance < new_distance)
+ return cpa;
+
+ /* drop the previous reference */
+ atomic_dec(&cpa->pa_count);
+ atomic_inc(&pa->pa_count);
+ return pa;
+}
+
/*
* search goal blocks in preallocated space
*/
@@ -3295,7 +3318,8 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
int order, i;
struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
struct ext4_locality_group *lg;
- struct ext4_prealloc_space *pa;
+ struct ext4_prealloc_space *pa, *cpa = NULL;
+ ext4_fsblk_t goal_block;
/* only data can be preallocated */
if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
@@ -3338,6 +3362,10 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
/* The max size of hash table is PREALLOC_TB_SIZE */
order = PREALLOC_TB_SIZE - 1;
+ goal_block = ac->ac_g_ex.fe_group * EXT4_BLOCKS_PER_GROUP(ac->ac_sb) +
+ ac->ac_g_ex.fe_start +
+ le32_to_cpu(EXT4_SB(ac->ac_sb)->s_es->s_first_data_block);
+
for (i = order; i < PREALLOC_TB_SIZE; i++) {
rcu_read_lock();
list_for_each_entry_rcu(pa, &lg->lg_prealloc_list[i],
@@ -3345,17 +3373,19 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
spin_lock(&pa->pa_lock);
if (pa->pa_deleted == 0 &&
pa->pa_free >= ac->ac_o_ex.fe_len) {
- atomic_inc(&pa->pa_count);
- ext4_mb_use_group_pa(ac, pa);
- spin_unlock(&pa->pa_lock);
- ac->ac_criteria = 20;
- rcu_read_unlock();
- return 1;
+
+ cpa = ext4_mb_check_group_pa(goal_block,
+ pa, cpa);
}
spin_unlock(&pa->pa_lock);
}
rcu_read_unlock();
}
+ if (cpa) {
+ ext4_mb_use_group_pa(ac, cpa);
+ ac->ac_criteria = 20;
+ return 1;
+ }
return 0;
}
diff --git a/fs/inode.c b/fs/inode.c
index b6726f6..d77f0ee 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -163,6 +163,7 @@ static struct inode *alloc_inode(struct super_block *sb)
mapping->a_ops = &empty_aops;
mapping->host = inode;
mapping->flags = 0;
+ mapping->writeback_index = 0;
mapping_set_gfp_mask(mapping, GFP_HIGHUSER_PAGECACHE);
mapping->assoc_mapping = NULL;
mapping->backing_dev_info = &default_backing_dev_info;
--
1.6.0.rc0.42.g186458.dirty
--
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