Josef Bacik
2011-Apr-12 12:55 UTC
[PATCH] Btrfs: avoid taking the chunk_mutex in do_chunk_alloc V2
Everytime we try to allocate disk space we try and see if we can pre-emptively
allocate a chunk, but in the common case we don''t allocate anything, so
there is
no sense in taking the chunk_mutex at all. So instead if we are allocating a
chunk, mark it in the space_info so we don''t get two people trying to
allocate
at the same time. Thanks,
Signed-off-by: Josef Bacik <josef@redhat.com>
---
V1->V2: Return in the case where we don''t need to allocate a chunk
instead of
going to out.
fs/btrfs/ctree.h | 5 +++--
fs/btrfs/extent-tree.c | 29 ++++++++++++++++++++++++-----
2 files changed, 27 insertions(+), 7 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0d00a07..a566780 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -740,10 +740,11 @@ struct btrfs_space_info {
*/
unsigned long reservation_progress;
- int full; /* indicates that we cannot allocate any more
+ int full:1; /* indicates that we cannot allocate any more
chunks for this space */
- int force_alloc; /* set if we need to force a chunk alloc for
+ int force_alloc:1; /* set if we need to force a chunk alloc for
this space */
+ int chunk_alloc:1; /* set if we are allocating a chunk */
struct list_head list;
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index f619c3c..362cc9b 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3020,6 +3020,7 @@ static int update_space_info(struct btrfs_fs_info *info,
u64 flags,
found->bytes_may_use = 0;
found->full = 0;
found->force_alloc = 0;
+ found->chunk_alloc = 0;
*space_info = found;
list_add_rcu(&found->list, &info->space_info);
atomic_set(&found->caching_threads, 0);
@@ -3273,10 +3274,9 @@ static int do_chunk_alloc(struct btrfs_trans_handle
*trans,
{
struct btrfs_space_info *space_info;
struct btrfs_fs_info *fs_info = extent_root->fs_info;
+ int wait_for_alloc = 0;
int ret = 0;
- mutex_lock(&fs_info->chunk_mutex);
-
flags = btrfs_reduce_alloc_profile(extent_root, flags);
space_info = __find_space_info(extent_root->fs_info, flags);
@@ -3287,21 +3287,40 @@ static int do_chunk_alloc(struct btrfs_trans_handle
*trans,
}
BUG_ON(!space_info);
+again:
spin_lock(&space_info->lock);
if (space_info->force_alloc)
force = 1;
if (space_info->full) {
spin_unlock(&space_info->lock);
- goto out;
+ return 0;
}
if (!force && !should_alloc_chunk(extent_root, space_info,
alloc_bytes)) {
spin_unlock(&space_info->lock);
- goto out;
+ return 0;
+ } else if (space_info->chunk_alloc) {
+ wait_for_alloc = 1;
+ } else {
+ space_info->chunk_alloc = 1;
}
spin_unlock(&space_info->lock);
+ mutex_lock(&fs_info->chunk_mutex);
+
+ /*
+ * The chunk_mutex is held throughout the entirety of a chunk
+ * allocation, so once we''ve acquired the chunk_mutex we know that
the
+ * other guy is done and we need to recheck and see if we should
+ * allocate.
+ */
+ if (wait_for_alloc) {
+ mutex_unlock(&fs_info->chunk_mutex);
+ wait_for_alloc = 0;
+ goto again;
+ }
+
/*
* If we have mixed data/metadata chunks we want to make sure we keep
* allocating mixed chunks instead of individual chunks.
@@ -3327,9 +3346,9 @@ static int do_chunk_alloc(struct btrfs_trans_handle
*trans,
space_info->full = 1;
else
ret = 1;
+ space_info->chunk_alloc = 0;
space_info->force_alloc = 0;
spin_unlock(&space_info->lock);
-out:
mutex_unlock(&extent_root->fs_info->chunk_mutex);
return ret;
}
--
1.7.2.3
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liubo
2011-Apr-13 01:19 UTC
Re: [PATCH] Btrfs: avoid taking the chunk_mutex in do_chunk_alloc V2
On 04/12/2011 08:55 PM, Josef Bacik wrote:> Everytime we try to allocate disk space we try and see if we can pre-emptively > allocate a chunk, but in the common case we don''t allocate anything, so there is > no sense in taking the chunk_mutex at all. So instead if we are allocating a > chunk, mark it in the space_info so we don''t get two people trying to allocate > at the same time. Thanks, >Reviewed-by: Liu Bo <liubo2009@cn.fujitsu.com>> Signed-off-by: Josef Bacik <josef@redhat.com> > --- > V1->V2: Return in the case where we don''t need to allocate a chunk instead of > going to out. > > fs/btrfs/ctree.h | 5 +++-- > fs/btrfs/extent-tree.c | 29 ++++++++++++++++++++++++----- > 2 files changed, 27 insertions(+), 7 deletions(-) > > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h > index 0d00a07..a566780 100644 > --- a/fs/btrfs/ctree.h > +++ b/fs/btrfs/ctree.h > @@ -740,10 +740,11 @@ struct btrfs_space_info { > */ > unsigned long reservation_progress; > > - int full; /* indicates that we cannot allocate any more > + int full:1; /* indicates that we cannot allocate any more > chunks for this space */ > - int force_alloc; /* set if we need to force a chunk alloc for > + int force_alloc:1; /* set if we need to force a chunk alloc for > this space */ > + int chunk_alloc:1; /* set if we are allocating a chunk */ > > struct list_head list; > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > index f619c3c..362cc9b 100644 > --- a/fs/btrfs/extent-tree.c > +++ b/fs/btrfs/extent-tree.c > @@ -3020,6 +3020,7 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags, > found->bytes_may_use = 0; > found->full = 0; > found->force_alloc = 0; > + found->chunk_alloc = 0; > *space_info = found; > list_add_rcu(&found->list, &info->space_info); > atomic_set(&found->caching_threads, 0); > @@ -3273,10 +3274,9 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans, > { > struct btrfs_space_info *space_info; > struct btrfs_fs_info *fs_info = extent_root->fs_info; > + int wait_for_alloc = 0; > int ret = 0; > > - mutex_lock(&fs_info->chunk_mutex); > - > flags = btrfs_reduce_alloc_profile(extent_root, flags); > > space_info = __find_space_info(extent_root->fs_info, flags); > @@ -3287,21 +3287,40 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans, > } > BUG_ON(!space_info); > > +again: > spin_lock(&space_info->lock); > if (space_info->force_alloc) > force = 1; > if (space_info->full) { > spin_unlock(&space_info->lock); > - goto out; > + return 0; > } > > if (!force && !should_alloc_chunk(extent_root, space_info, > alloc_bytes)) { > spin_unlock(&space_info->lock); > - goto out; > + return 0; > + } else if (space_info->chunk_alloc) { > + wait_for_alloc = 1; > + } else { > + space_info->chunk_alloc = 1; > } > spin_unlock(&space_info->lock); > > + mutex_lock(&fs_info->chunk_mutex); > + > + /* > + * The chunk_mutex is held throughout the entirety of a chunk > + * allocation, so once we''ve acquired the chunk_mutex we know that the > + * other guy is done and we need to recheck and see if we should > + * allocate. > + */ > + if (wait_for_alloc) { > + mutex_unlock(&fs_info->chunk_mutex); > + wait_for_alloc = 0; > + goto again; > + } > + > /* > * If we have mixed data/metadata chunks we want to make sure we keep > * allocating mixed chunks instead of individual chunks. > @@ -3327,9 +3346,9 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans, > space_info->full = 1; > else > ret = 1; > + space_info->chunk_alloc = 0; > space_info->force_alloc = 0; > spin_unlock(&space_info->lock); > -out: > mutex_unlock(&extent_root->fs_info->chunk_mutex); > return ret; > }-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html