On Wed, Nov 28, 2007 at 01:53:36PM -0500, Hideo AOKI wrote:
>
> +/**
> + * __skb_queue_purge_and_sub_memory_allocated
> + * - empty a list and subtruct memory allocation counter
> + * @sk: sk
> + * @list: list to empty
> + * Delete all buffers on an &sk_buff list and subtruct the
> + * truesize of the sk_buff for memory accounting. Each buffer
> + * is removed from the list and one reference dropped. This
> + * function does not take the list lock and the caller must
> + * hold the relevant locks to use it.
> + */
> +static inline void __skb_queue_purge_and_sub_memory_allocated(struct sock
> *sk,
> + struct sk_buff_head *list)
> +{
> + struct sk_buff *skb;
> + int purged_skb_size = 0;
> + while ((skb = __skb_dequeue(list)) != NULL) {
> + purged_skb_size += sk_datagram_pages(skb->truesize);
> + kfree_skb(skb);
> + }
> + atomic_sub(purged_skb_size, sk->sk_prot->memory_allocated);
> +}
Thanks, this is a lot better than before!
However, I'm still a little concerned about the effect of two more
atomic op's per packet that we're adding here. Hang on a sec, that
should've been Dave's line since atomic ops are cheap on x86 :)
But seriously, it's not so much that we have two more atomic op's
per packet, but we have two more writes to a single global counter
for each packet. This is going to really suck on SMP.
So what I'd like to see is a scheme that's similar to sk_forward_alloc.
The idea is that each socket allocates memory using mem_schedule and
then stores it in sk_forward_alloc. Each packet then only has to
add to/subtract from sk_forward_alloc.
There is one big problem with this though, UDP is not serialised like
TCP. So you can't just use sk_forward_alloc since it's not an atomic_t.
We'll need to think about this one a bit more.
Cheers,
--
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <[EMAIL PROTECTED]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
