Hello!
On 4/17/2017 2:19 AM, Michael S. Tsirkin wrote:
Applications that consume a batch of entries in one go
can benefit from ability to return some of them back
into the ring.
Add an API for that - assuming there's space. If there's no space
naturally we can't do this and have to drop entries, but this implies
ring is full so we'd likely drop some anyway.
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
Jason, in my mind the biggest issue with your batching patchset is the
backet drops on disconnect. This API will help avoid that in the common
Packet?
[...]
diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
index 783e7f5..5fbeab4 100644
--- a/include/linux/ptr_ring.h
+++ b/include/linux/ptr_ring.h
@@ -457,6 +457,63 @@ static inline int ptr_ring_init(struct ptr_ring *r, int
size, gfp_t gfp)
return 0;
}
+/*
+ * Return entries into ring. Destroy entries that don't fit.
+ *
+ * Note: this is expected to be a rare slow path operation.
+ *
+ * Note: producer lock is nested within consumer lock, so if you
+ * resize you must make sure all uses nest correctly.
+ * In particular if you consume ring in interrupt or BH context, you must
+ * disable interrupts/BH when doing so.
+ */
+static inline void ptr_ring_unconsume(struct ptr_ring *r, void **batch, int n,
+ void (*destroy)(void *))
+{
+ unsigned long flags;
+ int head;
+
+ spin_lock_irqsave(&(r)->consumer_lock, flags);
+ spin_lock(&(r)->producer_lock);
The innermost parens seem pointless here....
[...]
+done:
+ /* Destroy all entries left in the batch. */
+ while (n--) {
+ destroy(batch[n]);
+ }
Braces not needed here.
+ spin_unlock(&(r)->producer_lock);
+ spin_unlock_irqrestore(&(r)->consumer_lock, flags);
Same comment about the innermost parens...
[...]
MBR, Sergei
