linux.git/fs/f2fs/node.h, branch v3.17

f2fs: refactor flush_nat_entries codes for reducing NAT writes

2014-07-09T21:04:25+00:00

Although building NAT journal in cursum reduce the read/write work for NAT
block, but previous design leave us lower performance when write checkpoint
frequently for these cases:
1. if journal in cursum has already full, it's a bit of waste that we flush all
   nat entries to page for persistence, but not to cache any entries.
2. if journal in cursum is not full, we fill nat entries to journal util
   journal is full, then flush the left dirty entries to disk without merge
   journaled entries, so these journaled entries may be flushed to disk at next
   checkpoint but lost chance to flushed last time.

In this patch we merge dirty entries located in same NAT block to nat entry set,
and linked all set to list, sorted ascending order by entries' count of set.
Later we flush entries in sparse set into journal as many as we can, and then
flush merged entries to disk. In this way we can not only gain in performance,
but also save lifetime of flash device.

In my testing environment, it shows this patch can help to reduce NAT block
writes obviously. In hard disk test case: cost time of fsstress is stablely
reduced by about 5%.

1. virtual machine + hard disk:
fsstress -p 20 -n 200 -l 5
		node num	cp count	nodes/cp
based		4599.6		1803.0		2.551
patched		2714.6		1829.6		1.483

2. virtual machine + 32g micro SD card:
fsstress -p 20 -n 200 -l 1 -w -f chown=0 -f creat=4 -f dwrite=0
-f fdatasync=4 -f fsync=4 -f link=0 -f mkdir=4 -f mknod=4 -f rename=5
-f rmdir=5 -f symlink=0 -f truncate=4 -f unlink=5 -f write=0 -S

		node num	cp count	nodes/cp
based		84.5		43.7		1.933
patched		49.2		40.0		1.23

Our latency of merging op shows not bad when handling extreme case like:
merging a great number of dirty nats:
latency(ns)	dirty nat count
3089219		24922
5129423		27422
4000250		24523

change log from v1:
 o fix wrong logic in add_nat_entry when grab a new nat entry set.
 o swith to create slab cache in create_node_manager_caches.
 o use GFP_ATOMIC instead of GFP_NOFS to avoid potential long latency.

change log from v2:
 o make comment position more appropriate suggested by Jaegeuk Kim.

Signed-off-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: fix checkpatch warning

2014-05-07T01:21:59+00:00

fix the following checkpatch warning:
WARNING: do {} while (0) macros should not be semicolon terminated

Signed-off-by: Zhang Zhen 
Signed-off-by: Jaegeuk Kim

f2fs: split grab_cache_page and wait_on_page_writeback for node pages

2014-05-07T01:21:58+00:00

This patch splits grab_cache_page_write_begin into grab_cache_page and
wait_on_page_writeback for node pages.

This patch intends to enhance the latency to get node pages by alleviating
unnecessary wait_on_page_writeback.

Signed-off-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: adjust free mem size to flush dentry blocks

2014-05-07T01:21:55+00:00

If so many dirty dentry blocks are cached, not reached to the flush condition,
we should fall into livelock in balance_dirty_pages.
So, let's consider the mem size for the condition.

Signed-off-by: Jaegeuk Kim

f2fs: introduce raw_nat_from_node_info() to simplfy codes

2014-05-07T01:21:55+00:00

This patch introduce raw_nat_from_node_info() to simplfy some codes, and also
use exist function node_info_from_raw_nat() to do the same job.

Signed-off-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: skip unnecessary node writes during fsync

2014-03-20T13:10:11+00:00

If multiple redundant fsync calls are triggered, we don't need to write its
node pages with fsync mark continuously.

So, this patch adds FI_NEED_FSYNC to track whether the latest node block is
written with the fsync mark or not.
If the mark was set, a new fsync doesn't need to write a node block.
Otherwise, we should do a new node block with the mark for roll-forward
recovery.

Signed-off-by: Jaegeuk Kim

f2fs: remove unnecessary threshold

2014-03-20T13:10:09+00:00

The NM_WOUT_THRESHOLD is now obsolete since f2fs starts to control on a basis
of the memory footprint.

Signed-off-by: Jaegeuk Kim

f2fs: throttle the memory footprint with a sysfs entry

2014-03-20T13:10:09+00:00

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

f2fs: introduce f2fs_has_xattr_block for better readability

2014-03-18T00:29:46+00:00

This patch introduces a help function f2fs_has_xattr_block for better
readability.

Signed-off-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: fix to mark the checkpointed nat entry correctly

2014-02-24T07:00:40+00:00

The nat cache entry maintains a status whether it is checkpointed or not.
So, if a new cache entry is loaded from the last checkpoint,
nat_entry->checkpointed should be true.
If the cache entry is modified as being dirty, nat_entry->checkpoint should
be false.

Signed-off-by: Jaegeuk Kim