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Date: Fri, 20 Apr 2018 17:35:54 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>
CC: <linux-f2fs-devel@...ts.sourceforge.net>,
<linux-kernel@...r.kernel.org>, <chao@...nel.org>
Subject: Re: [PATCH] f2fs: sepearte hot/cold in free nid
On 2018/4/20 12:04, Chao Yu wrote:
> On 2018/4/20 11:37, Jaegeuk Kim wrote:
>> On 04/20, Chao Yu wrote:
>>> As most indirect node, dindirect node, and xattr node won't be updated
>>> after they are created, but inode node and other direct node will change
>>> more frequently, so store their nat entries mixedly in whole nat table
>>> will suffer:
>>> - fragment nat table soon due to different update rate
>>> - more nat block update due to fragmented nat table
>>>
>>> In order to solve above issue, we're trying to separate whole nat table to
>>> two part:
>>> a. Hot free nid area:
>>> - range: [nid #0, nid #x)
>>> - store node block address for
>>> * inode node
>>> * other direct node
>>> b. Cold free nid area:
>>> - range: [nid #x, max nid)
>>> - store node block address for
>>> * indirect node
>>> * dindirect node
>>> * xattr node
>>>
>>> Allocation strategy example:
>>>
>>> Free nid: '-'
>>> Used nid: '='
>>>
>>> 1. Initial status:
>>> Free Nids: |-----------------------------------------------------------------------|
>>> ^ ^ ^ ^
>>> Alloc Range: |---------------| |---------------|
>>> hot_start hot_end cold_start cold_end
>>>
>>> 2. Free nids have ran out:
>>> Free Nids: |===============-----------------------------------------===============|
>>> ^ ^ ^ ^
>>> Alloc Range: |===============| |===============|
>>> hot_start hot_end cold_start cold_end
>>>
>>> 3. Expand hot/cold area range:
>>> Free Nids: |===============-----------------------------------------===============|
>>> ^ ^ ^ ^
>>> Alloc Range: |===============----------------| |----------------===============|
>>> hot_start hot_end cold_start cold_end
>>>
>>> 4. Hot free nids have ran out:
>>> Free Nids: |===============================-------------------------===============|
>>> ^ ^ ^ ^
>>> Alloc Range: |===============================| |----------------===============|
>>> hot_start hot_end cold_start cold_end
>>>
>>> 5. Expand hot area range, hot/cold area boundary has been fixed:
>>> Free Nids: |===============================-------------------------===============|
>>> ^ ^ ^
>>> Alloc Range: |===============================--------|----------------===============|
>>> hot_start hot_end(cold_start) cold_end
>>>
>>> Run xfstests with generic/*:
>>>
>>> before
>>> node_write: 169660
>>> cp_count: 60118
>>> node/cp 2.82
>>>
>>> after:
>>> node_write: 159145
>>> cp_count: 84501
>>> node/cp: 2.64
>>
>> Nice trial tho, I don't see much benefit on this huge patch. I guess we may be
>> able to find an efficient way to achieve this issue rather than changing whole
>> stable codes.
>
> IMO, based on this, later, we can add more allocation policy to manage free nid
> resource to get more benefit.
>
> If you worry about code stability, we can queue this patch in dev-test branch to
> test this longer time.
>
>>
>> How about getting a free nid in the list from head or tail separately?
>
> I don't think this can get benefit from long time used image, since nat table
> will be fragmented anyway, then we won't know free nid in head or in tail comes
> from hot nat block or cold nat block.
>
> Anyway, I will have a try.
A quick test result with below patch:
node_write:187837, cp_count:76431
>From 9f88ea8a36a74f1d3ed8df57ceffb1b8ae41a161 Mon Sep 17 00:00:00 2001
From: Chao Yu <yuchao0@...wei.com>
Date: Fri, 20 Apr 2018 16:18:26 +0800
Subject: [PATCH] f2fs: separate hot/cold free nid simply
Signed-off-by: Chao Yu <yuchao0@...wei.com>
---
fs/f2fs/f2fs.h | 2 +-
fs/f2fs/namei.c | 2 +-
fs/f2fs/node.c | 14 +++++++++-----
fs/f2fs/xattr.c | 2 +-
4 files changed, 12 insertions(+), 8 deletions(-)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 7651a118faa3..adca5e8bc19a 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2800,7 +2800,7 @@ int fsync_node_pages(struct f2fs_sb_info *sbi, struct
inode *inode,
int sync_node_pages(struct f2fs_sb_info *sbi, struct writeback_control *wbc,
bool do_balance, enum iostat_type io_type);
void build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount);
-bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid);
+bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid, bool hot);
void alloc_nid_done(struct f2fs_sb_info *sbi, nid_t nid);
void alloc_nid_failed(struct f2fs_sb_info *sbi, nid_t nid);
int try_to_free_nids(struct f2fs_sb_info *sbi, int nr_shrink);
diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index 3d59149590f7..bbf6edbb7298 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -37,7 +37,7 @@ static struct inode *f2fs_new_inode(struct inode *dir, umode_t
mode)
return ERR_PTR(-ENOMEM);
f2fs_lock_op(sbi);
- if (!alloc_nid(sbi, &ino)) {
+ if (!alloc_nid(sbi, &ino, true)) {
f2fs_unlock_op(sbi);
err = -ENOSPC;
goto fail;
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index ea231f8a0cce..bbaae2f3461e 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -631,7 +631,7 @@ int get_dnode_of_data(struct dnode_of_data *dn, pgoff_t
index, int mode)
if (!nids[i] && mode == ALLOC_NODE) {
/* alloc new node */
- if (!alloc_nid(sbi, &(nids[i]))) {
+ if (!alloc_nid(sbi, &(nids[i]), i == 1)) {
err = -ENOSPC;
goto release_pages;
}
@@ -2108,7 +2108,7 @@ void build_free_nids(struct f2fs_sb_info *sbi, bool sync,
bool mount)
* from second parameter of this function.
* The returned nid could be used ino as well as nid when inode is created.
*/
-bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid)
+bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid, bool hot)
{
struct f2fs_nm_info *nm_i = NM_I(sbi);
struct free_nid *i = NULL;
@@ -2129,8 +2129,12 @@ bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid)
/* We should not use stale free nids created by build_free_nids */
if (nm_i->nid_cnt[FREE_NID] && !on_build_free_nids(nm_i)) {
f2fs_bug_on(sbi, list_empty(&nm_i->free_nid_list));
- i = list_first_entry(&nm_i->free_nid_list,
- struct free_nid, list);
+ if (hot)
+ i = list_first_entry(&nm_i->free_nid_list,
+ struct free_nid, list);
+ else
+ i = list_last_entry(&nm_i->free_nid_list,
+ struct free_nid, list);
*nid = i->nid;
__move_free_nid(sbi, i, FREE_NID, PREALLOC_NID);
@@ -2275,7 +2279,7 @@ int recover_xattr_data(struct inode *inode, struct page *page)
recover_xnid:
/* 2: update xattr nid in inode */
- if (!alloc_nid(sbi, &new_xnid))
+ if (!alloc_nid(sbi, &new_xnid, false))
return -ENOSPC;
set_new_dnode(&dn, inode, NULL, NULL, new_xnid);
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
index d847b2b11659..46c090614563 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -398,7 +398,7 @@ static inline int write_all_xattrs(struct inode *inode,
__u32 hsize,
int err = 0;
if (hsize > inline_size && !F2FS_I(inode)->i_xattr_nid)
- if (!alloc_nid(sbi, &new_nid))
+ if (!alloc_nid(sbi, &new_nid, false))
return -ENOSPC;
/* write to inline xattr */
--
2.15.0.55.gc2ece9dc4de6
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