The NIC device drivers are expected to use this small helper API, when
building up an array of objects/skbs to bulk free, while (loop)
processing objects to free. Objects to be free'ed later is added
(dev_free_waitlist_add) to an array and flushed if the array runs
full. After processing the array is flushed (dev_free_waitlist_flush).
The array should be stored on the local stack.
Usage e.g. during TX completion loop the NIC driver can replace
dev_consume_skb_any() with an "add" and after the loop a "flush".
For performance reasons the compiler should inline most of these
functions.
Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
---
include/linux/netdevice.h | 62 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 62 insertions(+)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 05b9a694e213..d0133e778314 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2935,6 +2935,68 @@ static inline void dev_consume_skb_any(struct sk_buff *skb)
__dev_kfree_skb_any(skb, SKB_REASON_CONSUMED);
}
+/* The NIC device drivers are expected to use this small helper API,
+ * when building up an array of objects/skbs to bulk free, while
+ * (loop) processing objects to free. Objects to be free'ed later is
+ * added (dev_free_waitlist_add) to an array and flushed if the array
+ * runs full. After processing the array is flushed (dev_free_waitlist_flush).
+ * The array should be stored on the local stack.
+ *
+ * Usage e.g. during TX completion loop the NIC driver can replace
+ * dev_consume_skb_any() with an "add" and after the loop a "flush".
+ *
+ * For performance reasons the compiler should inline most of these
+ * functions.
+ */
+struct dev_free_waitlist {
+ struct sk_buff **skbs;
+ unsigned int skb_cnt;
+};
+
+static void __dev_free_waitlist_bulkfree(struct dev_free_waitlist *wl)
+{
+ /* Cannot bulk free from interrupt context or with IRQs
+ * disabled, due to how SLAB bulk API works (and gain it's
+ * speedup). This can e.g. happen due to invocation from
+ * netconsole/netpoll.
+ */
+ if (unlikely(in_irq() || irqs_disabled())) {
+ int i;
+
+ for (i = 0; i < wl->skb_cnt; i++)
+ dev_consume_skb_irq(wl->skbs[i]);
+ } else {
+ /* Likely fastpath, don't call with cnt == 0 */
+ kfree_skb_bulk(wl->skbs, wl->skb_cnt);
+ }
+}
+
+static inline void dev_free_waitlist_flush(struct dev_free_waitlist *wl)
+{
+ /* Flush the waitlist, but only if any objects remain, as bulk
+ * freeing "zero" objects is not supported and plus it avoids
+ * pointless function calls.
+ */
+ if (likely(wl->skb_cnt))
+ __dev_free_waitlist_bulkfree(wl);
+}
+
+static __always_inline void dev_free_waitlist_add(struct dev_free_waitlist *wl,
+ struct sk_buff *skb,
+ unsigned int max)
+{
+ /* It is recommended that max is a builtin constant, as this
+ * saves one register when inlined. Catch offenders with:
+ * BUILD_BUG_ON(!__builtin_constant_p(max));
+ */
+ wl->skbs[wl->skb_cnt++] = skb;
+ if (wl->skb_cnt == max) {
+ /* Detect when waitlist array is full, then flush and reset */
+ __dev_free_waitlist_bulkfree(wl);
+ wl->skb_cnt = 0;
+ }
+}
+
int netif_rx(struct sk_buff *skb);
int netif_rx_ni(struct sk_buff *skb);
int netif_receive_skb_sk(struct sock *sk, struct sk_buff *skb);
--
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