Re: [PATCH 1/11] nfsd: ADD data structure infrastructure

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Mar 25, 2009 at 07:06:28PM +0530, Krishna Kumar wrote:
> From: Krishna Kumar <krkumar2@in.ibm.com>
> 
> ADD infrastructure in terms of new structures.
> 
> Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
> ---
> 
>  fs/nfsd/vfs.c |   35 +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
> 
> diff -ruNp org/fs/nfsd/vfs.c new1/fs/nfsd/vfs.c
> --- org/fs/nfsd/vfs.c	2009-03-25 17:31:39.000000000 +0530
> +++ new1/fs/nfsd/vfs.c	2009-03-25 17:39:43.000000000 +0530
> @@ -88,6 +88,41 @@ struct raparm_hbucket {
>  #define RAPARM_HASH_MASK	(RAPARM_HASH_SIZE-1)
>  static struct raparm_hbucket	raparm_hash[RAPARM_HASH_SIZE];
>  
> +/*
> + * This is a cache of file handles to quicken file lookup. This also
> + * helps prevent multiple open/close of a file when a client reads it.
> + *
> + * If you increase the number of cached files very much, you'll need to
> + * add a hash table here.
> + */
> +struct fhcache {
> +	struct fhcache		*p_next;
> +
> +	/* Hashed on this parameter */
> +	__u32			p_auth;
> +
> +	/* Cached information */
> +	struct file		*p_filp;
> +	struct svc_export	*p_exp;
> +
> +	/* Refcount for overwrite */
> +	atomic_t		p_count;
> +
> +	/* When this entry expires */
> +	unsigned long		p_expires;
> +
> +	unsigned int		p_hindex;
> +};
> +
> +struct fhcache_hbucket {
> +	struct fhcache		*pb_head;
> +	spinlock_t		pb_lock;
> +} ____cacheline_aligned_in_smp;

Hadn't run across __cacheline_aligned_in_smp before--so that just
assures an fhcache_hbucket gets its own cacheline, so that two cpu's
taking the spinlock on different buckets won't be fighting over the
cacheline?

--b.

> +
> +#define FHPARM_HASH_BITS	8
> +#define FHPARM_HASH_SIZE	(1<<FHPARM_HASH_BITS)
> +#define FHPARM_HASH_MASK	(FHPARM_HASH_SIZE-1)
> +
>  /* 
>   * Called from nfsd_lookup and encode_dirent. Check if we have crossed 
>   * a mount point.