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Date: Thu, 12 Apr 2018 15:02:50 +0100
From: Edward Cree <ecree@...arflare.com>
To: <linux-net-drivers@...arflare.com>,
David Miller <davem@...emloft.net>
CC: netdev <netdev@...r.kernel.org>
Subject: [PATCH net 2/2] sfc: limit ARFS workitems in flight per channel
A misconfigured system (e.g. with all interrupts affinitised to all CPUs)
may produce a storm of ARFS steering events. With the existing sfc ARFS
implementation, that could create a backlog of workitems that grinds the
system to a halt. To prevent this, limit the number of workitems that
may be in flight for a given SFC device to 8 (EFX_RPS_MAX_IN_FLIGHT), and
return EBUSY from our ndo_rx_flow_steer method if the limit is reached.
Given this limit, also store the workitems in an array of slots within the
struct efx_nic, rather than dynamically allocating for each request.
Signed-off-by: Edward Cree <ecree@...arflare.com>
---
drivers/net/ethernet/sfc/net_driver.h | 25 +++++++++++++++
drivers/net/ethernet/sfc/rx.c | 58 ++++++++++++++++++-----------------
2 files changed, 55 insertions(+), 28 deletions(-)
diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index 5e379a83c729..eea3808b3f25 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -733,6 +733,27 @@ struct efx_rss_context {
u32 rx_indir_table[128];
};
+#ifdef CONFIG_RFS_ACCEL
+/**
+ * struct efx_async_filter_insertion - Request to asynchronously insert a filter
+ * @net_dev: Reference to the netdevice
+ * @spec: The filter to insert
+ * @work: Workitem for this request
+ * @rxq_index: Identifies the channel for which this request was made
+ * @flow_id: Identifies the kernel-side flow for which this request was made
+ */
+struct efx_async_filter_insertion {
+ struct net_device *net_dev;
+ struct efx_filter_spec spec;
+ struct work_struct work;
+ u16 rxq_index;
+ u32 flow_id;
+};
+
+/* Maximum number of ARFS workitems that may be in flight on an efx_nic */
+#define EFX_RPS_MAX_IN_FLIGHT 8
+#endif /* CONFIG_RFS_ACCEL */
+
/**
* struct efx_nic - an Efx NIC
* @name: Device name (net device name or bus id before net device registered)
@@ -850,6 +871,8 @@ struct efx_rss_context {
* @rps_expire_channel: Next channel to check for expiry
* @rps_expire_index: Next index to check for expiry in
* @rps_expire_channel's @rps_flow_id
+ * @rps_slot_map: bitmap of in-flight entries in @rps_slot
+ * @rps_slot: array of ARFS insertion requests for efx_filter_rfs_work()
* @active_queues: Count of RX and TX queues that haven't been flushed and drained.
* @rxq_flush_pending: Count of number of receive queues that need to be flushed.
* Decremented when the efx_flush_rx_queue() is called.
@@ -1004,6 +1027,8 @@ struct efx_nic {
struct mutex rps_mutex;
unsigned int rps_expire_channel;
unsigned int rps_expire_index;
+ unsigned long rps_slot_map;
+ struct efx_async_filter_insertion rps_slot[EFX_RPS_MAX_IN_FLIGHT];
#endif
atomic_t active_queues;
diff --git a/drivers/net/ethernet/sfc/rx.c b/drivers/net/ethernet/sfc/rx.c
index 13b0eb71dbf3..9c593c661cbf 100644
--- a/drivers/net/ethernet/sfc/rx.c
+++ b/drivers/net/ethernet/sfc/rx.c
@@ -827,28 +827,13 @@ MODULE_PARM_DESC(rx_refill_threshold,
#ifdef CONFIG_RFS_ACCEL
-/**
- * struct efx_async_filter_insertion - Request to asynchronously insert a filter
- * @net_dev: Reference to the netdevice
- * @spec: The filter to insert
- * @work: Workitem for this request
- * @rxq_index: Identifies the channel for which this request was made
- * @flow_id: Identifies the kernel-side flow for which this request was made
- */
-struct efx_async_filter_insertion {
- struct net_device *net_dev;
- struct efx_filter_spec spec;
- struct work_struct work;
- u16 rxq_index;
- u32 flow_id;
-};
-
static void efx_filter_rfs_work(struct work_struct *data)
{
struct efx_async_filter_insertion *req = container_of(data, struct efx_async_filter_insertion,
work);
struct efx_nic *efx = netdev_priv(req->net_dev);
struct efx_channel *channel = efx_get_channel(efx, req->rxq_index);
+ int slot_idx = req - efx->rps_slot;
int rc;
rc = efx->type->filter_insert(efx, &req->spec, true);
@@ -878,8 +863,8 @@ static void efx_filter_rfs_work(struct work_struct *data)
}
/* Release references */
+ clear_bit(slot_idx, &efx->rps_slot_map);
dev_put(req->net_dev);
- kfree(req);
}
int efx_filter_rfs(struct net_device *net_dev, const struct sk_buff *skb,
@@ -888,22 +873,36 @@ int efx_filter_rfs(struct net_device *net_dev, const struct sk_buff *skb,
struct efx_nic *efx = netdev_priv(net_dev);
struct efx_async_filter_insertion *req;
struct flow_keys fk;
+ int slot_idx;
+ int rc;
- if (flow_id == RPS_FLOW_ID_INVALID)
- return -EINVAL;
+ /* find a free slot */
+ for (slot_idx = 0; slot_idx < EFX_RPS_MAX_IN_FLIGHT; slot_idx++)
+ if (!test_and_set_bit(slot_idx, &efx->rps_slot_map))
+ break;
+ if (slot_idx >= EFX_RPS_MAX_IN_FLIGHT)
+ return -EBUSY;
- if (!skb_flow_dissect_flow_keys(skb, &fk, 0))
- return -EPROTONOSUPPORT;
+ if (flow_id == RPS_FLOW_ID_INVALID) {
+ rc = -EINVAL;
+ goto out_clear;
+ }
- if (fk.basic.n_proto != htons(ETH_P_IP) && fk.basic.n_proto != htons(ETH_P_IPV6))
- return -EPROTONOSUPPORT;
- if (fk.control.flags & FLOW_DIS_IS_FRAGMENT)
- return -EPROTONOSUPPORT;
+ if (!skb_flow_dissect_flow_keys(skb, &fk, 0)) {
+ rc = -EPROTONOSUPPORT;
+ goto out_clear;
+ }
- req = kmalloc(sizeof(*req), GFP_ATOMIC);
- if (!req)
- return -ENOMEM;
+ if (fk.basic.n_proto != htons(ETH_P_IP) && fk.basic.n_proto != htons(ETH_P_IPV6)) {
+ rc = -EPROTONOSUPPORT;
+ goto out_clear;
+ }
+ if (fk.control.flags & FLOW_DIS_IS_FRAGMENT) {
+ rc = -EPROTONOSUPPORT;
+ goto out_clear;
+ }
+ req = efx->rps_slot + slot_idx;
efx_filter_init_rx(&req->spec, EFX_FILTER_PRI_HINT,
efx->rx_scatter ? EFX_FILTER_FLAG_RX_SCATTER : 0,
rxq_index);
@@ -933,6 +932,9 @@ int efx_filter_rfs(struct net_device *net_dev, const struct sk_buff *skb,
req->flow_id = flow_id;
schedule_work(&req->work);
return 0;
+out_clear:
+ clear_bit(slot_idx, &efx->rps_slot_map);
+ return rc;
}
bool __efx_filter_rfs_expire(struct efx_nic *efx, unsigned int quota)
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