mm/vmscan.c: remove cpu online notification for now (6b700b5b) · Commits · 戴 / test

kswapd kernel thread starts either with a CPU affinity set to the full cpu mask of its target node or without any affinity at all if the node is CPUless. There is a cpu hotplug callback (kswapd_cpu_online) that implements an elaborate way to update this mask when a cpu is onlined. It is not really clear whether there is any actual benefit from this scheme. Completely CPU-less NUMA nodes rarely gain a new CPU during runtime. Drop the code for that reason. If there is a real usecase then we can resurrect and simplify the code. [mhocko@suse.com rewrite changelog] Suggested-by:

Michal Hocko <mhocko@suse.org> Signed-off-by:

Wei Yang <richardw.yang@linux.intel.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Acked-by:

Michal Hocko <mhocko@suse.com> Cc: David Rientjes <rientjes@google.com> Link: http://lkml.kernel.org/r/20200218224422.3407-1-richardw.yang@linux.intel.com Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

+1 −26

Original line number	Diff line number	Diff line
		@@ -4030,27 +4030,6 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
		}
		#endif /* CONFIG_HIBERNATION */

		/* It's optimal to keep kswapds on the same CPUs as their memory, but
		not required for correctness. So if the last cpu in a node goes
		away, we get changed to run anywhere: as the first one comes back,
		restore their cpu bindings. */
		static int kswapd_cpu_online(unsigned int cpu)
		{
		int nid;

		for_each_node_state(nid, N_MEMORY) {
		pg_data_t *pgdat = NODE_DATA(nid);
		const struct cpumask *mask;

		mask = cpumask_of_node(pgdat->node_id);

		if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
		/* One of our CPUs online: restore mask */
		set_cpus_allowed_ptr(pgdat->kswapd, mask);
		}
		return 0;
		}

		/*
		* This kswapd start function will be called by init and node-hot-add.
		* On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
		@@ -4090,15 +4069,11 @@ void kswapd_stop(int nid)

		static int __init kswapd_init(void)
		{
		int nid, ret;
		int nid;

		swap_setup();
		for_each_node_state(nid, N_MEMORY)
		kswapd_run(nid);
		ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
		"mm/vmscan:online", kswapd_cpu_online,
		NULL);
		WARN_ON(ret < 0);
		return 0;
		}

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