5.15-stable review patch. If anyone has any objections, please let me know.
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From: Chuck Lever chuck.lever@oracle.com
[ Upstream commit 6df19411367a5fb4ef61854cbd1af269c077f917 ]
The checks in nfsd_file_acquire() and nfsd_file_put() that directly invoke filecache garbage collection are intended to keep cache occupancy between a low- and high-watermark. The reason to limit the capacity of the filecache is to keep filecache lookups reasonably fast.
However, invoking garbage collection at those points has some undesirable negative impacts. Files that are held open by NFSv4 clients often push the occupancy of the filecache over these watermarks. At that point:
- Every call to nfsd_file_acquire() and nfsd_file_put() results in an LRU walk. This has the same effect on lookup latency as long chains in the hash table. - Garbage collection will then run on every nfsd thread, causing a lot of unnecessary lock contention. - Limiting cache capacity pushes out files used only by NFSv3 clients, which are the type of files the filecache is supposed to help.
To address those negative impacts, remove the direct calls to the garbage collector. Subsequent patches will address maintaining lookup efficiency as cache capacity increases.
Suggested-by: Wang Yugui wangyugui@e16-tech.com Suggested-by: Dave Chinner david@fromorbit.com Reviewed-by: Jeff Layton jlayton@kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com --- fs/nfsd/filecache.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-)
diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 849c010c6ef61..7a02ff11b9ec1 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -28,8 +28,6 @@ #define NFSD_LAUNDRETTE_DELAY (2 * HZ)
#define NFSD_FILE_SHUTDOWN (1) -#define NFSD_FILE_LRU_THRESHOLD (4096UL) -#define NFSD_FILE_LRU_LIMIT (NFSD_FILE_LRU_THRESHOLD << 2)
/* We only care about NFSD_MAY_READ/WRITE for this cache */ #define NFSD_FILE_MAY_MASK (NFSD_MAY_READ|NFSD_MAY_WRITE) @@ -65,8 +63,6 @@ static struct fsnotify_group *nfsd_file_fsnotify_group; static atomic_long_t nfsd_filecache_count; static struct delayed_work nfsd_filecache_laundrette;
-static void nfsd_file_gc(void); - static void nfsd_file_schedule_laundrette(void) { @@ -343,9 +339,6 @@ nfsd_file_put(struct nfsd_file *nf) nfsd_file_schedule_laundrette(); } else nfsd_file_put_noref(nf); - - if (atomic_long_read(&nfsd_filecache_count) >= NFSD_FILE_LRU_LIMIT) - nfsd_file_gc(); }
struct nfsd_file * @@ -1054,8 +1047,7 @@ nfsd_do_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, nfsd_file_hashtbl[hashval].nfb_maxcount = max(nfsd_file_hashtbl[hashval].nfb_maxcount, nfsd_file_hashtbl[hashval].nfb_count); spin_unlock(&nfsd_file_hashtbl[hashval].nfb_lock); - if (atomic_long_inc_return(&nfsd_filecache_count) >= NFSD_FILE_LRU_THRESHOLD) - nfsd_file_gc(); + atomic_long_inc(&nfsd_filecache_count);
nf->nf_mark = nfsd_file_mark_find_or_create(nf); if (nf->nf_mark) {