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nfsd: dynamically allocate DRC entries

The existing code keeps a fixed-size cache of 1024 entries. This is much
too small for a busy server, and wastes memory on an idle one.  This
patch changes the code to dynamically allocate and free these cache
entries.

A cap on the number of entries is retained, but it's much larger than
the existing value and now scales with the amount of low memory in the
machine.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
master
Jeff Layton 9 years ago
committed by J. Bruce Fields
parent
commit
0338dd1572
  1. 125
      fs/nfsd/nfscache.c

125
fs/nfsd/nfscache.c

@ -10,17 +10,13 @@
#include <linux/slab.h>
#include <linux/sunrpc/clnt.h>
#include <linux/highmem.h>
#include "nfsd.h"
#include "cache.h"
/* Size of reply cache. Common values are:
* 4.3BSD: 128
* 4.4BSD: 256
* Solaris2: 1024
* DEC Unix: 512-4096
*/
#define CACHESIZE 1024
#define NFSDDBG_FACILITY NFSDDBG_REPCACHE
#define HASHSIZE 64
static struct hlist_head * cache_hash;
@ -28,6 +24,7 @@ static struct list_head lru_head;
static int cache_disabled = 1;
static struct kmem_cache *drc_slab;
static unsigned int num_drc_entries;
static unsigned int max_drc_entries;
/*
* Calculate the hash index from an XID.
@ -48,6 +45,34 @@ static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
*/
static DEFINE_SPINLOCK(cache_lock);
/*
* Put a cap on the size of the DRC based on the amount of available
* low memory in the machine.
*
* 64MB: 8192
* 128MB: 11585
* 256MB: 16384
* 512MB: 23170
* 1GB: 32768
* 2GB: 46340
* 4GB: 65536
* 8GB: 92681
* 16GB: 131072
*
* ...with a hard cap of 256k entries. In the worst case, each entry will be
* ~1k, so the above numbers should give a rough max of the amount of memory
* used in k.
*/
static unsigned int
nfsd_cache_size_limit(void)
{
unsigned int limit;
unsigned long low_pages = totalram_pages - totalhigh_pages;
limit = (16 * int_sqrt(low_pages)) << (PAGE_SHIFT-10);
return min_t(unsigned int, limit, 256*1024);
}
static struct svc_cacherep *
nfsd_reply_cache_alloc(void)
{
@ -68,6 +93,7 @@ nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
{
if (rp->c_type == RC_REPLBUFF)
kfree(rp->c_replvec.iov_base);
hlist_del(&rp->c_hash);
list_del(&rp->c_lru);
--num_drc_entries;
kmem_cache_free(drc_slab, rp);
@ -75,30 +101,18 @@ nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
int nfsd_reply_cache_init(void)
{
int i;
struct svc_cacherep *rp;
drc_slab = kmem_cache_create("nfsd_drc", sizeof(struct svc_cacherep),
0, 0, NULL);
if (!drc_slab)
goto out_nomem;
INIT_LIST_HEAD(&lru_head);
i = CACHESIZE;
num_drc_entries = 0;
while (i) {
rp = nfsd_reply_cache_alloc();
if (!rp)
goto out_nomem;
++num_drc_entries;
list_add(&rp->c_lru, &lru_head);
i--;
}
cache_hash = kcalloc (HASHSIZE, sizeof(struct hlist_head), GFP_KERNEL);
cache_hash = kcalloc(HASHSIZE, sizeof(struct hlist_head), GFP_KERNEL);
if (!cache_hash)
goto out_nomem;
INIT_LIST_HEAD(&lru_head);
max_drc_entries = nfsd_cache_size_limit();
num_drc_entries = 0;
cache_disabled = 0;
return 0;
out_nomem:
@ -191,7 +205,7 @@ nfsd_cache_search(struct svc_rqst *rqstp)
int
nfsd_cache_lookup(struct svc_rqst *rqstp)
{
struct svc_cacherep *rp;
struct svc_cacherep *rp, *found;
__be32 xid = rqstp->rq_xid;
u32 proto = rqstp->rq_prot,
vers = rqstp->rq_vers,
@ -210,38 +224,48 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
rtn = RC_DOIT;
rp = nfsd_cache_search(rqstp);
if (rp) {
nfsdstats.rchits++;
if (rp)
goto found_entry;
/* Try to use the first entry on the LRU */
if (!list_empty(&lru_head)) {
rp = list_first_entry(&lru_head, struct svc_cacherep, c_lru);
if (nfsd_cache_entry_expired(rp) ||
num_drc_entries >= max_drc_entries)
goto setup_entry;
}
nfsdstats.rcmisses++;
/* This loop shouldn't take more than a few iterations normally */
{
int safe = 0;
list_for_each_entry(rp, &lru_head, c_lru) {
if (rp->c_state != RC_INPROG)
break;
if (safe++ > CACHESIZE) {
printk("nfsd: loop in repcache LRU list\n");
cache_disabled = 1;
goto out;
}
spin_unlock(&cache_lock);
rp = nfsd_reply_cache_alloc();
if (!rp) {
dprintk("nfsd: unable to allocate DRC entry!\n");
return RC_DOIT;
}
spin_lock(&cache_lock);
++num_drc_entries;
/*
* Must search again just in case someone inserted one
* after we dropped the lock above.
*/
found = nfsd_cache_search(rqstp);
if (found) {
nfsd_reply_cache_free_locked(rp);
rp = found;
goto found_entry;
}
/* All entries on the LRU are in-progress. This should not happen */
if (&rp->c_lru == &lru_head) {
static int complaints;
printk(KERN_WARNING "nfsd: all repcache entries locked!\n");
if (++complaints > 5) {
printk(KERN_WARNING "nfsd: disabling repcache.\n");
cache_disabled = 1;
}
goto out;
}
/*
* We're keeping the one we just allocated. Are we now over the
* limit? Prune one off the tip of the LRU in trade for the one we
* just allocated if so.
*/
if (num_drc_entries >= max_drc_entries)
nfsd_reply_cache_free_locked(list_first_entry(&lru_head,
struct svc_cacherep, c_lru));
setup_entry:
nfsdstats.rcmisses++;
rqstp->rq_cacherep = rp;
rp->c_state = RC_INPROG;
rp->c_xid = xid;
@ -265,6 +289,7 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
return rtn;
found_entry:
nfsdstats.rchits++;
/* We found a matching entry which is either in progress or done. */
age = jiffies - rp->c_timestamp;
lru_put_end(rp);
@ -295,7 +320,7 @@ found_entry:
break;
default:
printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type);
rp->c_state = RC_UNUSED;
nfsd_reply_cache_free_locked(rp);
}
goto out;

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