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authorMeelap Shah <meelap@umich.edu>2007-07-17 04:04:39 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-17 10:23:07 -0700
commitc2f1a551dea8b37c2e0cb886885c250fb703e9d8 (patch)
tree11a5f256703d856017ceb2268bd02b7b510dee30
parent1e5140279f31e47d58ed6036ee61ba7a65710e63 (diff)
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: "J. Bruce Fields" <bfields@citi.umich.edu> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/nfsd/nfs4state.c26
-rw-r--r--include/linux/nfsd/nfsd.h1
-rw-r--r--mm/page_alloc.c1
3 files changed, 27 insertions, 1 deletions
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 9cc31eaf3857..46249886ea86 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -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
diff --git a/include/linux/nfsd/nfsd.h b/include/linux/nfsd/nfsd.h
index 0d8420497765..ce5e345a9bce 100644
--- a/include/linux/nfsd/nfsd.h
+++ b/include/linux/nfsd/nfsd.h
@@ -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);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1a889c3fec59..e2a10b957f23 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -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