Commit c2f1a551 authored by Meelap Shah's avatar Meelap Shah Committed by Linus Torvalds
Browse files

knfsd: nfsd4: vary maximum delegation limit based on RAM size 



Our original NFSv4 delegation policy was to give out a read delegation on any
open when it was possible to.

Since the lifetime of a delegation isn't limited to that of an open, a client
may quite reasonably hang on to a delegation as long as it has the inode
cached.  This becomes an obvious problem the first time a client's inode cache
approaches the size of the server's total memory.

Our first quick solution was to add a hard-coded limit.  This patch makes a
mild incremental improvement by varying that limit according to the server's
total memory size, allowing at most 4 delegations per megabyte of RAM.

My quick back-of-the-envelope calculation finds that in the worst case (where
every delegation is for a different inode), a delegation could take about
1.5K, which would make the worst case usage about 6% of memory.  The new limit
works out to be about the same as the old on a 1-gig server.

[akpm@linux-foundation.org: Don't needlessly bloat vmlinux]
[akpm@linux-foundation.org: Make it right for highmem machines]
Signed-off-by: default avatar"J. Bruce Fields" <bfields@citi.umich.edu>
Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1e514027

fs/nfsd/nfs4state.c

+25 −1
Original line number Diff line number Diff line
@@ -49,6 +49,7 @@ 
#include <linux/nfsd/state.h>

#include <linux/nfsd/xdr4.h>

#include <linux/namei.h>

#include <linux/swap.h>

#include <linux/mutex.h>

#include <linux/lockd/bind.h>

#include <linux/module.h>
@@ -150,6 +151,7 @@ get_nfs4_file(struct nfs4_file *fi) 
}



static int num_delegations;

unsigned int max_delegations;



/*

 * Open owner state (share locks)
@@ -193,7 +195,7 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_stateid *stp, struct svc_f 
	struct nfs4_callback *cb = &stp->st_stateowner->so_client->cl_callback;



	dprintk("NFSD alloc_init_deleg\n");

	if (num_delegations > STATEID_HASH_SIZE * 4)

	if (num_delegations > max_delegations)

		return NULL;

	dp = kmem_cache_alloc(deleg_slab, GFP_KERNEL);

	if (dp == NULL)
@@ -3197,6 +3199,27 @@ get_nfs4_grace_period(void) 
	return max(user_lease_time, lease_time) * HZ;

}



/*

 * Since the lifetime of a delegation isn't limited to that of an open, a

 * client may quite reasonably hang on to a delegation as long as it has

 * the inode cached.  This becomes an obvious problem the first time a

 * client's inode cache approaches the size of the server's total memory.

 *

 * For now we avoid this problem by imposing a hard limit on the number

 * of delegations, which varies according to the server's memory size.

 */

static void

set_max_delegations(void)

{

	/*

	 * Allow at most 4 delegations per megabyte of RAM.  Quick

	 * estimates suggest that in the worst case (where every delegation

	 * is for a different inode), a delegation could take about 1.5K,

	 * giving a worst case usage of about 6% of memory.

	 */

	max_delegations = nr_free_buffer_pages() >> (20 - 2 - PAGE_SHIFT);

}



/* initialization to perform when the nfsd service is started: */



static void
@@ -3212,6 +3235,7 @@ __nfs4_state_start(void) 
	       grace_time/HZ);

	laundry_wq = create_singlethread_workqueue("nfsd4");

	queue_delayed_work(laundry_wq, &laundromat_work, grace_time);

	set_max_delegations();

}



int

include/linux/nfsd/nfsd.h

+1 −0
Original line number Diff line number Diff line
@@ -148,6 +148,7 @@ extern int nfsd_max_blksize; 
 * NFSv4 State

 */

#ifdef CONFIG_NFSD_V4

extern unsigned int max_delegations;

void nfs4_state_init(void);

int nfs4_state_start(void);

void nfs4_state_shutdown(void);

mm/page_alloc.c

+1 −0
Original line number Diff line number Diff line
@@ -1484,6 +1484,7 @@ unsigned int nr_free_buffer_pages(void) 
{

	return nr_free_zone_pages(gfp_zone(GFP_USER));

}

EXPORT_SYMBOL_GPL(nr_free_buffer_pages);



/*

 * Amount of free RAM allocatable within all zones

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