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f2fs: give a chance to merge IOs by IO scheduler

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Previously, background GC submits many 4KB read requests to load victim blocks
and/or its (i)node blocks.

...
f2fs_gc : f2fs_readpage: ino = 1, page_index = 0xb61, blkaddr = 0x3b964ed
f2fs_gc : block_rq_complete: 8,16 R () 499854968 + 8 [0]
f2fs_gc : f2fs_readpage: ino = 1, page_index = 0xb6f, blkaddr = 0x3b964ee
f2fs_gc : block_rq_complete: 8,16 R () 499854976 + 8 [0]
f2fs_gc : f2fs_readpage: ino = 1, page_index = 0xb79, blkaddr = 0x3b964ef
f2fs_gc : block_rq_complete: 8,16 R () 499854984 + 8 [0]
...

However, by the fact that many IOs are sequential, we can give a chance to merge
the IOs by IO scheduler.
In order to do that, let's use blk_plug.

...
f2fs_gc : f2fs_iget: ino = 143
f2fs_gc : f2fs_readpage: ino = 143, page_index = 0x1c6, blkaddr = 0x2e6ee
f2fs_gc : f2fs_iget: ino = 143
f2fs_gc : f2fs_readpage: ino = 143, page_index = 0x1c7, blkaddr = 0x2e6ef
<idle> : block_rq_complete: 8,16 R () 1519616 + 8 [0]
<idle> : block_rq_complete: 8,16 R () 1519848 + 8 [0]
<idle> : block_rq_complete: 8,16 R () 1520432 + 96 [0]
<idle> : block_rq_complete: 8,16 R () 1520536 + 104 [0]
<idle> : block_rq_complete: 8,16 R () 1521008 + 112 [0]
<idle> : block_rq_complete: 8,16 R () 1521440 + 152 [0]
<idle> : block_rq_complete: 8,16 R () 1521688 + 144 [0]
<idle> : block_rq_complete: 8,16 R () 1522128 + 192 [0]
<idle> : block_rq_complete: 8,16 R () 1523256 + 328 [0]
...

Note that this issue should be addressed in checkpoint, and some readahead
flows too.

Reviewed-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
This commit is contained in:
Jaegeuk Kim
2013-04-24 13:19:56 +09:00
parent 6cb968d9b0
commit c718379b6b
7 changed files with 36 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
fs/f2fs/gc.c
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@@ -386,6 +386,7 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
next_step:
entry = sum;
for (off = 0; off < sbi->blocks_per_seg; off++, entry++) {
nid_t nid = le32_to_cpu(entry->nid);
struct page *node_page;
@@ -417,6 +418,7 @@ next_step:
f2fs_put_page(node_page, 1);
stat_inc_node_blk_count(sbi, 1);
}
if (initial) {
initial = false;
goto next_step;
@@ -545,6 +547,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
next_step:
entry = sum;
for (off = 0; off < sbi->blocks_per_seg; off++, entry++) {
struct page *data_page;
struct inode *inode;
@@ -582,7 +585,7 @@ next_step:
continue;
data_page = find_data_page(inode,
start_bidx + ofs_in_node);
start_bidx + ofs_in_node, false);
if (IS_ERR(data_page))
goto next_iput;
@@ -603,6 +606,7 @@ next_step:
next_iput:
iput(inode);
}
if (++phase < 4)
goto next_step;
@@ -636,12 +640,15 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
{
struct page *sum_page;
struct f2fs_summary_block *sum;
struct blk_plug plug;
/* read segment summary of victim */
sum_page = get_sum_page(sbi, segno);
if (IS_ERR(sum_page))
return;
blk_start_plug(&plug);
sum = page_address(sum_page);
switch (GET_SUM_TYPE((&sum->footer))) {
@@ -652,6 +659,8 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
gc_data_segment(sbi, sum->entries, ilist, segno, gc_type);
break;
}
blk_finish_plug(&plug);
stat_inc_seg_count(sbi, GET_SUM_TYPE((&sum->footer)));
stat_inc_call_count(sbi->stat_info);