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Commit 8fdc929f authored by Chris Metcalf's avatar Chris Metcalf Committed by David S. Miller
Browse files

dynticks: avoid flow_cache_flush() interrupting every core 



Previously, if you did an "ifconfig down" or similar on one core, and
the kernel had CONFIG_XFRM enabled, every core would be interrupted to
check its percpu flow list for items that could be garbage collected.

With this change, we generate a mask of cores that actually have any
percpu items, and only interrupt those cores.  When we are trying to
isolate a set of cpus from interrupts, this is important to do.

Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7fa6f340

net/core/flow.c

+39 −3
Original line number Diff line number Diff line
@@ -323,6 +323,24 @@ static void flow_cache_flush_tasklet(unsigned long data) 
		complete(&info->completion);

}



/*

 * Return whether a cpu needs flushing.  Conservatively, we assume

 * the presence of any entries means the core may require flushing,

 * since the flow_cache_ops.check() function may assume it's running

 * on the same core as the per-cpu cache component.

 */

static int flow_cache_percpu_empty(struct flow_cache *fc, int cpu)

{

	struct flow_cache_percpu *fcp;

	int i;



	fcp = &per_cpu(*fc->percpu, cpu);

	for (i = 0; i < flow_cache_hash_size(fc); i++)

		if (!hlist_empty(&fcp->hash_table[i]))

			return 0;

	return 1;

}



static void flow_cache_flush_per_cpu(void *data)

{

	struct flow_flush_info *info = data;
@@ -337,22 +355,40 @@ void flow_cache_flush(void) 
{

	struct flow_flush_info info;

	static DEFINE_MUTEX(flow_flush_sem);

	cpumask_var_t mask;

	int i, self;



	/* Track which cpus need flushing to avoid disturbing all cores. */

	if (!alloc_cpumask_var(&mask, GFP_KERNEL))

		return;

	cpumask_clear(mask);



	/* Don't want cpus going down or up during this. */

	get_online_cpus();

	mutex_lock(&flow_flush_sem);

	info.cache = &flow_cache_global;

	atomic_set(&info.cpuleft, num_online_cpus());

	for_each_online_cpu(i)

		if (!flow_cache_percpu_empty(info.cache, i))

			cpumask_set_cpu(i, mask);

	atomic_set(&info.cpuleft, cpumask_weight(mask));

	if (atomic_read(&info.cpuleft) == 0)

		goto done;



	init_completion(&info.completion);



	local_bh_disable();

	smp_call_function(flow_cache_flush_per_cpu, &info, 0);

	self = cpumask_test_and_clear_cpu(smp_processor_id(), mask);

	on_each_cpu_mask(mask, flow_cache_flush_per_cpu, &info, 0);

	if (self)

		flow_cache_flush_tasklet((unsigned long)&info);

	local_bh_enable();



	wait_for_completion(&info.completion);



done:

	mutex_unlock(&flow_flush_sem);

	put_online_cpus();

	free_cpumask_var(mask);

}



static void flow_cache_flush_task(struct work_struct *work)