NFSv4: Limit the total number of cached delegations (10717f45) · Commits · 戴 / test

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 <trond.myklebust@hammerspace.com> Signed-off-by:

Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/delegation.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -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);

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