Re: [RFC PATCH] add lookup hint for network file systems

[Andrew Morton <akpm@osdl.org>]

On Fri, 23 Jun 2006 21:04:30 +0900 (JST)
ASANO Masahiro <masano@tnes.nec.co.jp> wrote:

> Hi,
> 
> I'm trying to speeding up mkdir(2) for network file systems.
> A typical mkdir(2) calls two inode_operations: lookup and mkdir.
> The lookup operation would fail with ENOENT in common case.  I think
> it is unnecessary because the subsequent mkdir operation can check it.
> In case of creat(2), lookup operation is called with the LOOKUP_CREATE
> flag, so individual filesystem can omit real lookup. e.g. nfs_lookup().
> 
> Here is a sample patch which uses LOOKUP_CREATE and O_EXCL on mkdir,
> symlink and mknod.  This uses the gadget for creat(2).
> 
> And here is the result of a benchmark on NFSv3.
>   mkdir(2) 10,000 times:
>     original  50.5 sec
>     patched   29.0 sec
> 
> Signed-off-by: ASANO Masahiro <masano@tnes.nec.co.jp>
> 
> ---
> 
>  fs/namei.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> 5273ee304b4dc1096432dc3f3aa9183e20afab1d
> diff --git a/fs/namei.c b/fs/namei.c
> index 184fe4a..209867d 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -1759,6 +1759,8 @@ struct dentry *lookup_create(struct name
>  	if (nd->last_type != LAST_NORM)
>  		goto fail;
>  	nd->flags &= ~LOOKUP_PARENT;
> +	nd->flags |= LOOKUP_CREATE;
> +	nd->intent.open.flags = O_EXCL;
>  
>  	/*
>  	 * Do the final lookup.

whoa.  Big patch ;)

I'll save it up for when Trond returns, thanks.