| Message ID | 1426162823-31760-1-git-send-email-jbacik@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu 12-03-15 08:20:23, Josef Bacik wrote: > Some filesystems don't use the VFS inode hash and fake the fact they > are hashed so that all the writeback code works correctly. However, > this means the evict() path still tries to remove the inode from the > hash, meaning that the inode_hash_lock() needs to be taken > unnecessarily. Hence under certain workloads the inode_hash_lock can > be contended even if the inode is never actually hashed. > > To avoid this add hlist_fake to test if the inode isn't actually > hashed to avoid taking the hash lock on inodes that have never been > hashed. Based on Dave Chinner's > > inode: add IOP_NOTHASHED to avoid inode hash lock in evict > > basd on Al's suggestions. Thanks, > > Signed-off-by: Josef Bacik <jbacik@fb.com> Looks good. You can add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > V1->V2: Argh sorry, forgot to reset the author, my bad. > > include/linux/fs.h | 2 +- > include/linux/list.h | 5 +++++ > 2 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index b4d71b5..31da757 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -2528,7 +2528,7 @@ static inline void insert_inode_hash(struct inode *inode) > extern void __remove_inode_hash(struct inode *); > static inline void remove_inode_hash(struct inode *inode) > { > - if (!inode_unhashed(inode)) > + if (!inode_unhashed(inode) && !hlist_fake(&inode->i_hash)) > __remove_inode_hash(inode); > } > > diff --git a/include/linux/list.h b/include/linux/list.h > index feb773c..3e3e64a 100644 > --- a/include/linux/list.h > +++ b/include/linux/list.h > @@ -672,6 +672,11 @@ static inline void hlist_add_fake(struct hlist_node *n) > n->pprev = &n->next; > } > > +static inline bool hlist_fake(struct hlist_node *h) > +{ > + return h->pprev == &h->next; > +} > + > /* > * Move a list from one list head to another. Fixup the pprev > * reference of the first entry if it exists. > -- > 1.9.3 >
diff --git a/include/linux/fs.h b/include/linux/fs.h index b4d71b5..31da757 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2528,7 +2528,7 @@ static inline void insert_inode_hash(struct inode *inode) extern void __remove_inode_hash(struct inode *); static inline void remove_inode_hash(struct inode *inode) { - if (!inode_unhashed(inode)) + if (!inode_unhashed(inode) && !hlist_fake(&inode->i_hash)) __remove_inode_hash(inode); } diff --git a/include/linux/list.h b/include/linux/list.h index feb773c..3e3e64a 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -672,6 +672,11 @@ static inline void hlist_add_fake(struct hlist_node *n) n->pprev = &n->next; } +static inline bool hlist_fake(struct hlist_node *h) +{ + return h->pprev == &h->next; +} + /* * Move a list from one list head to another. Fixup the pprev * reference of the first entry if it exists.
Some filesystems don't use the VFS inode hash and fake the fact they are hashed so that all the writeback code works correctly. However, this means the evict() path still tries to remove the inode from the hash, meaning that the inode_hash_lock() needs to be taken unnecessarily. Hence under certain workloads the inode_hash_lock can be contended even if the inode is never actually hashed. To avoid this add hlist_fake to test if the inode isn't actually hashed to avoid taking the hash lock on inodes that have never been hashed. Based on Dave Chinner's inode: add IOP_NOTHASHED to avoid inode hash lock in evict basd on Al's suggestions. Thanks, Signed-off-by: Josef Bacik <jbacik@fb.com> --- V1->V2: Argh sorry, forgot to reset the author, my bad. include/linux/fs.h | 2 +- include/linux/list.h | 5 +++++ 2 files changed, 6 insertions(+), 1 deletion(-)