From 124906fa0d1a804e238ee94d16c88deb6ef576f8 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Mon, 27 Jan 2020 09:58:19 -0500 Subject: [PATCH] NFSv4: Limit the total number of cached delegations Delegations can be expensive to return, and can cause scalability issues for the server. Let's therefore try to limit the number of inactive delegations we hold. Once the number of delegations is above a certain threshold, start to return them on close. Signed-off-by: Trond Myklebust Signed-off-by: Anna Schumaker --- fs/nfs/delegation.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c index a777b3d0e7204..4a841071d8a71 100644 --- a/fs/nfs/delegation.c +++ b/fs/nfs/delegation.c @@ -25,7 +25,10 @@ #include "internal.h" #include "nfs4trace.h" +#define NFS_DEFAULT_DELEGATION_WATERMARK (5000U) + static atomic_long_t nfs_active_delegations; +static unsigned nfs_delegation_watermark = NFS_DEFAULT_DELEGATION_WATERMARK; static void __nfs_free_delegation(struct nfs_delegation *delegation) { @@ -676,7 +679,8 @@ void nfs4_inode_return_delegation_on_close(struct inode *inode) delegation = nfs4_get_valid_delegation(inode); if (!delegation) goto out; - if (test_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags)) { + if (test_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags) || + atomic_long_read(&nfs_active_delegations) >= nfs_delegation_watermark) { spin_lock(&delegation->lock); if (delegation->inode && list_empty(&NFS_I(inode)->open_files) && @@ -1365,3 +1369,5 @@ out: rcu_read_unlock(); return ret; } + +module_param_named(delegation_watermark, nfs_delegation_watermark, uint, 0644); -- 2.39.5