quoted

What not pass a list of skbs (e.g. using skb->next)?

Because the next layer, the slab API needs an array:
  kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)

I suppose we could ask the same question of that function. IMO
encouraging drivers to define arrays of pointers on the stack like
you're doing in the ixgbe patch is a bad direction.

In any case I believe this would be simpler in the networking side
just to maintain a list of skb's to free. Then the dev_free_waitlist
structure might not be needed then since we could just use a
skb_buf_head for that.


Tom

Look at the patch:
 [PATCH V2 3/3] slub: build detached freelist with look-ahead
 http://thread.gmane.org/gmane.linux.kernel.mm/137469/focus=137472

Where I use this array to progressively scan for objects belonging to
the same page.  (A subtle detail is I manage to zero out the array,
which is good from a security/error-handling point of view, as pointers
to the objects are not left dangling on the stack).


I cannot argue that, writing skb->next comes as an additional cost,
because the slUb free also writes into this cacheline.  Perhaps the
slAb allocator does not?

[...]

quoted

quoted

+       if (likely(cnt)) {
+               kmem_cache_free_bulk(skbuff_head_cache, cnt, (void **) skbs);
+       }
+}
+EXPORT_SYMBOL(kfree_skb_bulk);

--
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Sr. Network Kernel Developer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer

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