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nfsd: add recurring workqueue job to clean the cache 

It's not sufficient to only clean the cache when requests come in. What
if we have a flurry of activity and then the server goes idle? Add a
workqueue job that will clean the cache every RC_EXPIRE period.

Care is taken to only run this when we expect to have entries expiring.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Jeff Layton 2013-02-04 08:18:05 -05:00 committed by J. Bruce Fields
parent 2c6b691c05
commit aca8a23de6
1 changed files with 47 additions and 3 deletions
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50
fs/nfsd/nfscache.c
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@ -36,6 +36,7 @@ static inline u32 request_hash(u32 xid)
}
static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
static void cache_cleaner_func(struct work_struct *unused);
/*
* locking for the reply cache:
@ -43,6 +44,7 @@ static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
* Otherwise, it when accessing _prev or _next, the lock must be held.
*/
static DEFINE_SPINLOCK(cache_lock);
static DECLARE_DELAYED_WORK(cache_cleaner, cache_cleaner_func);
/*
* Put a cap on the size of the DRC based on the amount of available
@ -131,6 +133,8 @@ void nfsd_reply_cache_shutdown(void)
{
struct svc_cacherep *rp;
cancel_delayed_work_sync(&cache_cleaner);
while (!list_empty(&lru_head)) {
rp = list_entry(lru_head.next, struct svc_cacherep, c_lru);
nfsd_reply_cache_free_locked(rp);
@ -146,13 +150,15 @@ void nfsd_reply_cache_shutdown(void)
}
/*
* Move cache entry to end of LRU list
* Move cache entry to end of LRU list, and queue the cleaner to run if it's
* not already scheduled.
*/
static void
lru_put_end(struct svc_cacherep *rp)
{
rp->c_timestamp = jiffies;
list_move_tail(&rp->c_lru, &lru_head);
schedule_delayed_work(&cache_cleaner, RC_EXPIRE);
}
/*
@ -172,6 +178,42 @@ nfsd_cache_entry_expired(struct svc_cacherep *rp)
time_after(jiffies, rp->c_timestamp + RC_EXPIRE);
}
/*
* Walk the LRU list and prune off entries that are older than RC_EXPIRE.
* Also prune the oldest ones when the total exceeds the max number of entries.
*/
static void
prune_cache_entries(void)
{
struct svc_cacherep *rp, *tmp;
list_for_each_entry_safe(rp, tmp, &lru_head, c_lru) {
if (!nfsd_cache_entry_expired(rp) &&
num_drc_entries <= max_drc_entries)
break;
nfsd_reply_cache_free_locked(rp);
}
/*
* Conditionally rearm the job. If we cleaned out the list, then
* cancel any pending run (since there won't be any work to do).
* Otherwise, we rearm the job or modify the existing one to run in
* RC_EXPIRE since we just ran the pruner.
*/
if (list_empty(&lru_head))
cancel_delayed_work(&cache_cleaner);
else
mod_delayed_work(system_wq, &cache_cleaner, RC_EXPIRE);
}
static void
cache_cleaner_func(struct work_struct *unused)
{
spin_lock(&cache_lock);
prune_cache_entries();
spin_unlock(&cache_lock);
}
/*
* Search the request hash for an entry that matches the given rqstp.
* Must be called with cache_lock held. Returns the found entry or
@ -192,7 +234,6 @@ nfsd_cache_search(struct svc_rqst *rqstp)
hlist_for_each_entry(rp, hn, rh, c_hash) {
if (xid == rp->c_xid && proc == rp->c_proc &&
proto == rp->c_prot && vers == rp->c_vers &&
!nfsd_cache_entry_expired(rp) &&
rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) &&
rpc_get_port(svc_addr(rqstp)) == rpc_get_port((struct sockaddr *)&rp->c_addr))
return rp;
@ -234,8 +275,11 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
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)
num_drc_entries >= max_drc_entries) {
lru_put_end(rp);
prune_cache_entries();
goto setup_entry;
}
}
spin_unlock(&cache_lock);