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net: fix XPS static_key accounting

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Commit 04157469b7 ("net: Use static_key for XPS maps") introduced a
static key for XPS, but the increments/decrements don't match.

First, the static key's counter is incremented once for each queue, but
only decremented once for a whole batch of queues, leading to large
unbalances.

Second, the xps_rxqs_needed key is decremented whenever we reset a batch
of queues, whether they had any rxqs mapping or not, so that if we setup
cpu-XPS on em1 and RXQS-XPS on em2, resetting the queues on em1 would
decrement the xps_rxqs_needed key.

This reworks the accounting scheme so that the xps_needed key is
incremented only once for each type of XPS for all the queues on a
device, and the xps_rxqs_needed key is incremented only once for all
queues. This is sufficient to let us retrieve queues via
get_xps_queue().

This patch introduces a new reset_xps_maps(), which reinitializes and
frees the appropriate map (xps_rxqs_map or xps_cpus_map), and drops a
reference to the needed keys:
 - both xps_needed and xps_rxqs_needed, in case of rxqs maps,
 - only xps_needed, in case of CPU maps.

Now, we also need to call reset_xps_maps() at the end of
__netif_set_xps_queue() when there's no active map left, for example
when writing '00000000,00000000' to all queues' xps_rxqs setting.

Fixes: 04157469b7 ("net: Use static_key for XPS maps")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Sabrina Dubroca 2018-11-29 14:14:49 +01:00 committed by David S. Miller
parent f28c020fb4
commit 867d0ad476
1 changed files with 24 additions and 21 deletions
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45
net/core/dev.c
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@ -2175,6 +2175,20 @@ static bool remove_xps_queue_cpu(struct net_device *dev,
return active;
}
static void reset_xps_maps(struct net_device *dev,
struct xps_dev_maps *dev_maps,
bool is_rxqs_map)
{
if (is_rxqs_map) {
static_key_slow_dec_cpuslocked(&xps_rxqs_needed);
RCU_INIT_POINTER(dev->xps_rxqs_map, NULL);
} else {
RCU_INIT_POINTER(dev->xps_cpus_map, NULL);
}
static_key_slow_dec_cpuslocked(&xps_needed);
kfree_rcu(dev_maps, rcu);
}
static void clean_xps_maps(struct net_device *dev, const unsigned long *mask,
struct xps_dev_maps *dev_maps, unsigned int nr_ids,
u16 offset, u16 count, bool is_rxqs_map)
@ -2186,13 +2200,8 @@ static void clean_xps_maps(struct net_device *dev, const unsigned long *mask,
j < nr_ids;)
active |= remove_xps_queue_cpu(dev, dev_maps, j, offset,
count);
if (!active) {
if (is_rxqs_map)
RCU_INIT_POINTER(dev->xps_rxqs_map, NULL);
else
RCU_INIT_POINTER(dev->xps_cpus_map, NULL);
kfree_rcu(dev_maps, rcu);
}
if (!active)
reset_xps_maps(dev, dev_maps, is_rxqs_map);
if (!is_rxqs_map) {
for (i = offset + (count - 1); count--; i--) {
@ -2236,10 +2245,6 @@ static void netif_reset_xps_queues(struct net_device *dev, u16 offset,
false);
out_no_maps:
if (static_key_enabled(&xps_rxqs_needed))
static_key_slow_dec_cpuslocked(&xps_rxqs_needed);
static_key_slow_dec_cpuslocked(&xps_needed);
mutex_unlock(&xps_map_mutex);
cpus_read_unlock();
}
@ -2357,9 +2362,12 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
if (!new_dev_maps)
goto out_no_new_maps;
static_key_slow_inc_cpuslocked(&xps_needed);
if (is_rxqs_map)
static_key_slow_inc_cpuslocked(&xps_rxqs_needed);
if (!dev_maps) {
/* Increment static keys at most once per type */
static_key_slow_inc_cpuslocked(&xps_needed);
if (is_rxqs_map)
static_key_slow_inc_cpuslocked(&xps_rxqs_needed);
}
for (j = -1; j = netif_attrmask_next(j, possible_mask, nr_ids),
j < nr_ids;) {
@ -2457,13 +2465,8 @@ out_no_new_maps:
}
/* free map if not active */
if (!active) {
if (is_rxqs_map)
RCU_INIT_POINTER(dev->xps_rxqs_map, NULL);
else
RCU_INIT_POINTER(dev->xps_cpus_map, NULL);
kfree_rcu(dev_maps, rcu);
}
if (!active)
reset_xps_maps(dev, dev_maps, is_rxqs_map);
out_no_maps:
mutex_unlock(&xps_map_mutex);