Re: [PATCH] Btrfs: skip setting path to blocking mode if balance is not needed

2018-09-14 Thread David Sterba 
On Wed, Sep 12, 2018 at 09:51:33AM +0300, Nikolay Borisov wrote:
> 
> 
> On 12.09.2018 01:06, Liu Bo wrote:
> > balance_level() may return early in some cases, but these checks don't
> > have to be done with blocking write lock.
> > 
> > This puts together these checks into a helper and the benefit is to
> > avoid switching spinning locks to blocking locks (in these paticular
> > cases) which slows down btrfs overall.
> 
> Performance patches without numbers are frowned upon. You need to
> substantiate your claims.
> 
> 
> > 
> > Signed-off-by: Liu Bo 
> > ---
> >  fs/btrfs/ctree.c | 41 ++---
> >  1 file changed, 30 insertions(+), 11 deletions(-)
> > 
> > diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
> > index 858085490e23..ba267a069ca1 100644
> > --- a/fs/btrfs/ctree.c
> > +++ b/fs/btrfs/ctree.c
> > @@ -1758,6 +1758,29 @@ static void root_sub_used(struct btrfs_root *root, 
> > u32 size)
> > return eb;
> >  }
> >  
> > +static bool need_balance_level(struct btrfs_fs_info *fs_info,
> 
> nit: I think should_balance_level seems more readable, but it could be
> just me so won't insist on that.

Quick grep shows that should_ is used more frequently, so I'd go with
that.

Re: [PATCH] Btrfs: skip setting path to blocking mode if balance is not needed

2018-09-12 Thread Nikolay Borisov 



On 12.09.2018 01:06, Liu Bo wrote:
> balance_level() may return early in some cases, but these checks don't
> have to be done with blocking write lock.
> 
> This puts together these checks into a helper and the benefit is to
> avoid switching spinning locks to blocking locks (in these paticular
> cases) which slows down btrfs overall.

Performance patches without numbers are frowned upon. You need to
substantiate your claims.


> 
> Signed-off-by: Liu Bo 
> ---
>  fs/btrfs/ctree.c | 41 ++---
>  1 file changed, 30 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
> index 858085490e23..ba267a069ca1 100644
> --- a/fs/btrfs/ctree.c
> +++ b/fs/btrfs/ctree.c
> @@ -1758,6 +1758,29 @@ static void root_sub_used(struct btrfs_root *root, u32 
> size)
>   return eb;
>  }
>  
> +static bool need_balance_level(struct btrfs_fs_info *fs_info,

nit: I think should_balance_level seems more readable, but it could be
just me so won't insist on that.

> +   struct btrfs_trans_handle *trans,
> +   struct btrfs_path *path, int level)
> +{
> + struct extent_buffer *mid;
> +
> + mid = path->nodes[level];
> +
> + WARN_ON(path->locks[level] != BTRFS_WRITE_LOCK &&
> + path->locks[level] != BTRFS_WRITE_LOCK_BLOCKING);
> + WARN_ON(btrfs_header_generation(mid) != trans->transid);
> +
> + /* If mid is the root node. */
> + if (level < BTRFS_MAX_LEVEL - 1 && path->nodes[level + 1] == NULL)
> + if (btrfs_header_nritems(mid) != 1)
> + return false;
> +
> + if (btrfs_header_nritems(mid) > BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 4)
> + return false;
> +
> + return true;
> +}
> +
>  /*
>   * node level balancing, used to make sure nodes are in proper order for
>   * item deletion.  We balance from the top down, so we have to make sure
> @@ -1780,10 +1803,6 @@ static noinline int balance_level(struct 
> btrfs_trans_handle *trans,
>  
>   mid = path->nodes[level];
>  
> - WARN_ON(path->locks[level] != BTRFS_WRITE_LOCK &&
> - path->locks[level] != BTRFS_WRITE_LOCK_BLOCKING);
> - WARN_ON(btrfs_header_generation(mid) != trans->transid);
> -
>   orig_ptr = btrfs_node_blockptr(mid, orig_slot);
>  
>   if (level < BTRFS_MAX_LEVEL - 1) {
> @@ -1798,9 +1817,6 @@ static noinline int balance_level(struct 
> btrfs_trans_handle *trans,
>   if (!parent) {
>   struct extent_buffer *child;
>  
> - if (btrfs_header_nritems(mid) != 1)
> - return 0;
> -
>   /* promote the child to a root */
>   child = read_node_slot(fs_info, mid, 0);
>   if (IS_ERR(child)) {
> @@ -1838,9 +1854,6 @@ static noinline int balance_level(struct 
> btrfs_trans_handle *trans,
>   free_extent_buffer_stale(mid);
>   return 0;
>   }
> - if (btrfs_header_nritems(mid) >
> - BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 4)
> - return 0;
>  
>   left = read_node_slot(fs_info, parent, pslot - 1);
>   if (IS_ERR(left))
> @@ -2460,14 +2473,20 @@ noinline void btrfs_unlock_up_safe(struct btrfs_path 
> *path, int level)
>   goto again;
>   }
>  
> + /* Skip setting path to blocking if balance is not needed. */
> + if (!need_balance_level(fs_info, trans, p, level)) {
> + ret = 0;
> + goto done;
> + }
> +
>   btrfs_set_path_blocking(p);
>   reada_for_balance(fs_info, p, level);
>   sret = balance_level(trans, root, p, level);
> -
>   if (sret) {
>   ret = sret;
>   goto done;
>   }
> +
>   b = p->nodes[level];
>   if (!b) {
>   btrfs_release_path(p);
>

[PATCH] Btrfs: skip setting path to blocking mode if balance is not needed

2018-09-11 Thread Liu Bo 
balance_level() may return early in some cases, but these checks don't
have to be done with blocking write lock.

This puts together these checks into a helper and the benefit is to
avoid switching spinning locks to blocking locks (in these paticular
cases) which slows down btrfs overall.

Signed-off-by: Liu Bo 
---
 fs/btrfs/ctree.c | 41 ++---
 1 file changed, 30 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 858085490e23..ba267a069ca1 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1758,6 +1758,29 @@ static void root_sub_used(struct btrfs_root *root, u32 
size)
return eb;
 }
 
+static bool need_balance_level(struct btrfs_fs_info *fs_info,
+ struct btrfs_trans_handle *trans,
+ struct btrfs_path *path, int level)
+{
+   struct extent_buffer *mid;
+
+   mid = path->nodes[level];
+
+   WARN_ON(path->locks[level] != BTRFS_WRITE_LOCK &&
+   path->locks[level] != BTRFS_WRITE_LOCK_BLOCKING);
+   WARN_ON(btrfs_header_generation(mid) != trans->transid);
+
+   /* If mid is the root node. */
+   if (level < BTRFS_MAX_LEVEL - 1 && path->nodes[level + 1] == NULL)
+   if (btrfs_header_nritems(mid) != 1)
+   return false;
+
+   if (btrfs_header_nritems(mid) > BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 4)
+   return false;
+
+   return true;
+}
+
 /*
  * node level balancing, used to make sure nodes are in proper order for
  * item deletion.  We balance from the top down, so we have to make sure
@@ -1780,10 +1803,6 @@ static noinline int balance_level(struct 
btrfs_trans_handle *trans,
 
mid = path->nodes[level];
 
-   WARN_ON(path->locks[level] != BTRFS_WRITE_LOCK &&
-   path->locks[level] != BTRFS_WRITE_LOCK_BLOCKING);
-   WARN_ON(btrfs_header_generation(mid) != trans->transid);
-
orig_ptr = btrfs_node_blockptr(mid, orig_slot);
 
if (level < BTRFS_MAX_LEVEL - 1) {
@@ -1798,9 +1817,6 @@ static noinline int balance_level(struct 
btrfs_trans_handle *trans,
if (!parent) {
struct extent_buffer *child;
 
-   if (btrfs_header_nritems(mid) != 1)
-   return 0;
-
/* promote the child to a root */
child = read_node_slot(fs_info, mid, 0);
if (IS_ERR(child)) {
@@ -1838,9 +1854,6 @@ static noinline int balance_level(struct 
btrfs_trans_handle *trans,
free_extent_buffer_stale(mid);
return 0;
}
-   if (btrfs_header_nritems(mid) >
-   BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 4)
-   return 0;
 
left = read_node_slot(fs_info, parent, pslot - 1);
if (IS_ERR(left))
@@ -2460,14 +2473,20 @@ noinline void btrfs_unlock_up_safe(struct btrfs_path 
*path, int level)
goto again;
}
 
+   /* Skip setting path to blocking if balance is not needed. */
+   if (!need_balance_level(fs_info, trans, p, level)) {
+   ret = 0;
+   goto done;
+   }
+
btrfs_set_path_blocking(p);
reada_for_balance(fs_info, p, level);
sret = balance_level(trans, root, p, level);
-
if (sret) {
ret = sret;
goto done;
}
+
b = p->nodes[level];
if (!b) {
btrfs_release_path(p);
-- 
1.8.3.1