Re: [PATCH 10/44] nfsd41: change from page to memory based drc limits

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

On Tue, Jun 16, 2009 at 04:19:41AM +0300, Benny Halevy wrote:
> From: Andy Adamson <andros@netapp.com>
> 
> NFSD_SLOT_CACHE_SIZE is the size of all encoded operation responses (excluding
> the sequence operation) that we want to cache.
> 
> Adjust NFSD_DRC_SIZE_SHIFT to reflect using 512 bytes instead of PAGE_SIZE.
> 
> Signed-off-by: Andy Adamson <andros@netapp.com>
> Signed-off-by: Benny Halevy <bhalevy@panasas.com>
> ---
>  fs/nfsd/nfs4state.c        |   29 +++++++++++++++--------------
>  fs/nfsd/nfssvc.c           |   13 +++++++------
>  include/linux/nfsd/state.h |    1 +
>  include/linux/sunrpc/svc.h |    4 ++--
>  4 files changed, 25 insertions(+), 22 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 90e6645..6489913 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -416,33 +416,34 @@ gen_sessionid(struct nfsd4_session *ses)
>   * Give the client the number of slots it requests bound by
>   * NFSD_MAX_SLOTS_PER_SESSION and by sv_drc_max_pages.
>   *
> - * If we run out of pages (sv_drc_pages_used == sv_drc_max_pages) we
> - * should (up to a point) re-negotiate active sessions and reduce their
> - * slot usage to make rooom for new connections. For now we just fail the
> - * create session.
> + * If we run out of reserved DRC memory we should (up to a point) re-negotiate
> + * active sessions and reduce their slot usage to make rooom for new
> + * connections. For now we just fail the create session.
>   */
>  static int set_forechannel_maxreqs(struct nfsd4_channel_attrs *fchan)
>  {
> -	int status = 0, np = fchan->maxreqs * NFSD_PAGES_PER_SLOT;
> +	int mem;
>  
>  	if (fchan->maxreqs < 1)
>  		return nfserr_inval;
>  	else if (fchan->maxreqs > NFSD_MAX_SLOTS_PER_SESSION)
>  		fchan->maxreqs = NFSD_MAX_SLOTS_PER_SESSION;
>  
> +	mem = fchan->maxreqs * NFSD_SLOT_CACHE_SIZE;
> +
>  	spin_lock(&nfsd_serv->sv_lock);
> -	if (np + nfsd_serv->sv_drc_pages_used > nfsd_serv->sv_drc_max_pages)
> -		np = nfsd_serv->sv_drc_max_pages - nfsd_serv->sv_drc_pages_used;
> -	nfsd_serv->sv_drc_pages_used += np;
> +	if (mem + nfsd_serv->sv_drc_mem_used > nfsd_serv->sv_drc_max_mem)
> +		mem = nfsd_serv->sv_drc_max_mem - nfsd_serv->sv_drc_mem_used;
> +	nfsd_serv->sv_drc_mem_used += mem;
>  	spin_unlock(&nfsd_serv->sv_lock);
>  
> -	if (np <= 0) {
> -		status = nfserr_resource;
> +	if (mem < NFSD_SLOT_CACHE_SIZE) {
>  		fchan->maxreqs = 0;
> -	} else
> -		fchan->maxreqs = np / NFSD_PAGES_PER_SLOT;
> -
> -	return status;
> +		return nfserr_resource;
> +	} else {
> +		fchan->maxreqs = mem / NFSD_SLOT_CACHE_SIZE;
> +		return 0;

Simpler:  just

	fchan->maxreqs = mem / NFSD_SLOT_CACHE_SIZE;
	if (fchan->maxreqs == 0)
		status = nfserr_resource;

--b.

> +	}
>  }
>  
>  /*
> diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
> index cbba4a9..80588cc 100644
> --- a/fs/nfsd/nfssvc.c
> +++ b/fs/nfsd/nfssvc.c
> @@ -237,12 +237,13 @@ void nfsd_reset_versions(void)
>  static void set_max_drc(void)
>  {
>  	/* The percent of nr_free_buffer_pages used by the V4.1 server DRC */
> -	#define NFSD_DRC_SIZE_SHIFT	7
> -	nfsd_serv->sv_drc_max_pages = nr_free_buffer_pages()
> -						>> NFSD_DRC_SIZE_SHIFT;
> -	nfsd_serv->sv_drc_pages_used = 0;
> -	dprintk("%s svc_drc_max_pages %u\n", __func__,
> -		nfsd_serv->sv_drc_max_pages);
> +	#define NFSD_DRC_SIZE_SHIFT	10
> +	nfsd_serv->sv_drc_max_mem = (nr_free_buffer_pages()
> +					>> NFSD_DRC_SIZE_SHIFT) * PAGE_SIZE;
> +	nfsd_serv->sv_drc_mem_used = 0;
> +	dprintk("%s svc_drc_max_mem %u [in pages %lu]\n", __func__,
> +		nfsd_serv->sv_drc_max_mem,
> +		nfsd_serv->sv_drc_max_mem / PAGE_SIZE);
>  }
>  
>  int nfsd_create_serv(void)
> diff --git a/include/linux/nfsd/state.h b/include/linux/nfsd/state.h
> index eae086c..1ebb05e 100644
> --- a/include/linux/nfsd/state.h
> +++ b/include/linux/nfsd/state.h
> @@ -96,6 +96,7 @@ struct nfs4_cb_conn {
>  #define NFSD_MAX_SLOTS_PER_SESSION	128
>  /* Maximum number of pages per slot cache entry */
>  #define NFSD_PAGES_PER_SLOT	1
> +#define NFSD_SLOT_CACHE_SIZE		512
>  /* Maximum number of operations per session compound */
>  #define NFSD_MAX_OPS_PER_COMPOUND	16
>  
> diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
> index 2a30775..243508e 100644
> --- a/include/linux/sunrpc/svc.h
> +++ b/include/linux/sunrpc/svc.h
> @@ -94,8 +94,8 @@ struct svc_serv {
>  	struct module *		sv_module;	/* optional module to count when
>  						 * adding threads */
>  	svc_thread_fn		sv_function;	/* main function for threads */
> -	unsigned int		sv_drc_max_pages; /* Total pages for DRC */
> -	unsigned int		sv_drc_pages_used;/* DRC pages used */
> +	unsigned int		sv_drc_max_mem; /* Total pages for DRC */
> +	unsigned int		sv_drc_mem_used;/* DRC pages used */
>  };
>  
>  /*
> -- 
> 1.6.3
>