SUNRPC: Fix a performance regression in the RPC authentication code (23918b03) · Commits · 戴 / test

Fix a regression reported by Max Kellermann whereby kernel profiling showed that his clients were spending 45% of their time in rpcauth_lookup_credcache. It turns out that although his processes had identical uid/gid/groups, generic_match() was failing to detect this, because the task->group_info pointers were not shared. This again lead to the creation of a huge number of identical credentials at the RPC layer. The regression is fixed by comparing the contents of task->group_info if the actual pointers are not identical. Signed-off-by:

Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

net/sunrpc/auth_generic.c

+18 −2

Original line number	Diff line number	Diff line
		@@ -133,13 +133,29 @@ static int
		generic_match(struct auth_cred acred, struct rpc_cred cred, int flags)
		{
		struct generic_cred *gcred = container_of(cred, struct generic_cred, gc_base);
		int i;

		if (gcred->acred.uid != acred->uid \|\|
		gcred->acred.gid != acred->gid \|\|
		gcred->acred.group_info != acred->group_info \|\|
		gcred->acred.machine_cred != acred->machine_cred)
		return 0;
		goto out_nomatch;

		/* Optimisation in the case where pointers are identical... */
		if (gcred->acred.group_info == acred->group_info)
		goto out_match;

		/* Slow path... */
		if (gcred->acred.group_info->ngroups != acred->group_info->ngroups)
		goto out_nomatch;
		for (i = 0; i < gcred->acred.group_info->ngroups; i++) {
		if (GROUP_AT(gcred->acred.group_info, i) !=
		GROUP_AT(acred->group_info, i))
		goto out_nomatch;
		}
		out_match:
		return 1;
		out_nomatch:
		return 0;
		}

		void __init rpc_init_generic_auth(void)

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