>From e5c6600d01c4462c4e1ee0c70ec1d9319862077d Mon Sep 17 00:00:00 2001
From: Chao Yu <[email protected]>
Date: Thu, 2 Jul 2015 18:52:46 +0800
Subject: [PATCH] f2fs: reduce lock overhead of extent node releasing
Open and close critical section for each extent node when traversing rb-tree
results in high overhead of cpu, slows thing down.
This patch alternates to batch mode for removing extent nodes under spin lock.
Signed-off-by: Chao Yu <[email protected]>
---
fs/f2fs/data.c | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 deletions(-)
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 6a706dd..7fb56a0 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -441,19 +441,31 @@ static unsigned int __free_extent_tree(struct f2fs_sb_info *sbi,
struct extent_node *en;
unsigned int count = et->count;
- node = rb_first(&et->root);
- while (node) {
- next = rb_next(node);
- en = rb_entry(node, struct extent_node, rb_node);
+ if (!et->count)
+ return 0;
+
+ /* 1. remove all extent nodes in global lru list */
+ if (free_all) {
+ spin_lock(&sbi->extent_lock);
+ node = rb_first(&et->root);
+ while (node) {
+ next = rb_next(node);
+ en = rb_entry(node, struct extent_node, rb_node);
- if (free_all) {
- spin_lock(&sbi->extent_lock);
if (!list_empty(&en->list))
list_del_init(&en->list);
- spin_unlock(&sbi->extent_lock);
+ node = next;
}
+ spin_unlock(&sbi->extent_lock);
+ }
+
+ /* 2. release all extent nodes which are not in global lru list */
+ node = rb_first(&et->root);
+ while (node) {
+ next = rb_next(node);
+ en = rb_entry(node, struct extent_node, rb_node);
- if (free_all || list_empty(&en->list)) {
+ if (list_empty(&en->list)) {
__detach_extent_node(sbi, et, en);
kmem_cache_free(extent_node_slab, en);
}
--
2.4.2
On Thu, Jul 02, 2015 at 08:40:12PM +0800, Chao Yu wrote:
> >From e5c6600d01c4462c4e1ee0c70ec1d9319862077d Mon Sep 17 00:00:00 2001
> From: Chao Yu <[email protected]>
> Date: Thu, 2 Jul 2015 18:52:46 +0800
> Subject: [PATCH] f2fs: reduce lock overhead of extent node releasing
>
> Open and close critical section for each extent node when traversing rb-tree
> results in high overhead of cpu, slows thing down.
>
> This patch alternates to batch mode for removing extent nodes under spin lock.
>
> Signed-off-by: Chao Yu <[email protected]>
> ---
> fs/f2fs/data.c | 28 ++++++++++++++++++++--------
> 1 file changed, 20 insertions(+), 8 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 6a706dd..7fb56a0 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -441,19 +441,31 @@ static unsigned int __free_extent_tree(struct f2fs_sb_info *sbi,
> struct extent_node *en;
> unsigned int count = et->count;
>
> - node = rb_first(&et->root);
> - while (node) {
> - next = rb_next(node);
> - en = rb_entry(node, struct extent_node, rb_node);
> + if (!et->count)
> + return 0;
> +
> + /* 1. remove all extent nodes in global lru list */
> + if (free_all) {
> + spin_lock(&sbi->extent_lock);
> + node = rb_first(&et->root);
> + while (node) {
> + next = rb_next(node);
> + en = rb_entry(node, struct extent_node, rb_node);
>
> - if (free_all) {
> - spin_lock(&sbi->extent_lock);
> if (!list_empty(&en->list))
> list_del_init(&en->list);
> - spin_unlock(&sbi->extent_lock);
> + node = next;
> }
> + spin_unlock(&sbi->extent_lock);
> + }
> +
> + /* 2. release all extent nodes which are not in global lru list */
Hmm,
Is there any overhead to traverse the rb_tree twice and any spin_lock delay
caused by contention?
Thanks,
> + node = rb_first(&et->root);
> + while (node) {
> + next = rb_next(node);
> + en = rb_entry(node, struct extent_node, rb_node);
>
> - if (free_all || list_empty(&en->list)) {
> + if (list_empty(&en->list)) {
> __detach_extent_node(sbi, et, en);
> kmem_cache_free(extent_node_slab, en);
> }
> --
> 2.4.2
> -----Original Message-----
> From: Jaegeuk Kim [mailto:[email protected]]
> Sent: Saturday, July 04, 2015 3:04 PM
> To: Chao Yu
> Cc: [email protected]; [email protected]
> Subject: Re: [f2fs-dev] [PATCH] f2fs: reduce lock overhead of extent node releasing
>
> On Thu, Jul 02, 2015 at 08:40:12PM +0800, Chao Yu wrote:
> > >From e5c6600d01c4462c4e1ee0c70ec1d9319862077d Mon Sep 17 00:00:00 2001
> > From: Chao Yu <[email protected]>
> > Date: Thu, 2 Jul 2015 18:52:46 +0800
> > Subject: [PATCH] f2fs: reduce lock overhead of extent node releasing
> >
> > Open and close critical section for each extent node when traversing rb-tree
> > results in high overhead of cpu, slows thing down.
> >
> > This patch alternates to batch mode for removing extent nodes under spin lock.
> >
> > Signed-off-by: Chao Yu <[email protected]>
> > ---
> > fs/f2fs/data.c | 28 ++++++++++++++++++++--------
> > 1 file changed, 20 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 6a706dd..7fb56a0 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -441,19 +441,31 @@ static unsigned int __free_extent_tree(struct f2fs_sb_info *sbi,
> > struct extent_node *en;
> > unsigned int count = et->count;
> >
> > - node = rb_first(&et->root);
> > - while (node) {
> > - next = rb_next(node);
> > - en = rb_entry(node, struct extent_node, rb_node);
> > + if (!et->count)
> > + return 0;
> > +
> > + /* 1. remove all extent nodes in global lru list */
> > + if (free_all) {
> > + spin_lock(&sbi->extent_lock);
> > + node = rb_first(&et->root);
> > + while (node) {
> > + next = rb_next(node);
> > + en = rb_entry(node, struct extent_node, rb_node);
> >
> > - if (free_all) {
> > - spin_lock(&sbi->extent_lock);
> > if (!list_empty(&en->list))
> > list_del_init(&en->list);
> > - spin_unlock(&sbi->extent_lock);
> > + node = next;
> > }
> > + spin_unlock(&sbi->extent_lock);
> > + }
> > +
> > + /* 2. release all extent nodes which are not in global lru list */
>
> Hmm,
> Is there any overhead to traverse the rb_tree twice and
Yes, it will cost us more time to traverse the rb tree twice, adding one more
shrink list may reduce the overhead.
> any spin_lock delay caused by contention?
Maybe, since our critical region is enlarged, but the overhead of operation
for re-entering the critical region will be decreased as we invoke spin_lock
only one time.
Thanks,
>
> Thanks,
>
> > + node = rb_first(&et->root);
> > + while (node) {
> > + next = rb_next(node);
> > + en = rb_entry(node, struct extent_node, rb_node);
> >
> > - if (free_all || list_empty(&en->list)) {
> > + if (list_empty(&en->list)) {
> > __detach_extent_node(sbi, et, en);
> > kmem_cache_free(extent_node_slab, en);
> > }
> > --
> > 2.4.2
>
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