Re: [PATCH] inode: don't memset the inode address space twice

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Mar 02, 2018 at 09:34:02AM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> Noticed when looking at why cycling 600k inodes/s through the inode
> cache was taking a total of 8% cpu in memset() during inode
> initialisation.  There is no need to zero the inode.i_data structure
> twice.
> 
> This increases single threaded bulkstat throughput from ~200,000
> inodes/s to ~220,000 inodes/s, so we save a substantial amount of
> CPU time per inode init by doing this.
> 
> Signed-Off-By: Dave Chinner <dchinner@redhat.com>

Looks ok, will test...
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/inode.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index 6295f1415761..b153aeaa61ea 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -346,9 +346,8 @@ void inc_nlink(struct inode *inode)
>  }
>  EXPORT_SYMBOL(inc_nlink);
>  
> -void address_space_init_once(struct address_space *mapping)
> +static void __address_space_init_once(struct address_space *mapping)
>  {
> -	memset(mapping, 0, sizeof(*mapping));
>  	INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC | __GFP_ACCOUNT);
>  	spin_lock_init(&mapping->tree_lock);
>  	init_rwsem(&mapping->i_mmap_rwsem);
> @@ -356,6 +355,12 @@ void address_space_init_once(struct address_space *mapping)
>  	spin_lock_init(&mapping->private_lock);
>  	mapping->i_mmap = RB_ROOT_CACHED;
>  }
> +
> +void address_space_init_once(struct address_space *mapping)
> +{
> +	memset(mapping, 0, sizeof(*mapping));
> +	__address_space_init_once(mapping);
> +}
>  EXPORT_SYMBOL(address_space_init_once);
>  
>  /*
> @@ -371,7 +376,7 @@ void inode_init_once(struct inode *inode)
>  	INIT_LIST_HEAD(&inode->i_io_list);
>  	INIT_LIST_HEAD(&inode->i_wb_list);
>  	INIT_LIST_HEAD(&inode->i_lru);
> -	address_space_init_once(&inode->i_data);
> +	__address_space_init_once(&inode->i_data);
>  	i_size_ordered_init(inode);
>  }
>  EXPORT_SYMBOL(inode_init_once);
> -- 
> 2.16.1
>