Re: [PATCH][RFC 23/23]: Support for zero-copy TCP transmit of userspace data

[Vladislav Bolkhovitin]

Evgeniy Polyakov, on 12/24/2008 12:38 AM wrote:
> On Tue, Dec 23, 2008 at 10:16:25PM +0300, Vladislav Bolkhovitin (vst@xxxxxxxx) wrote:
> > Actually, there's another way, which seems to be a lot simpler. Alexey 
> > Kuznetsov privately suggested it to me.
> >
> > In skb_shared_info new pointer transaction_token would be added, which 
> > would point on:
> >
> > struct sk_transaction_token
> > {
> > 	atomic_t			io_count;
> > 	struct sk_transaction_token	*next;
> > 	unsigned long			token;
> > 	unsigned long			private;
> > 	void				(*finish_callback)(struct 
> > 	sk_transaction_token *);
> > };
> >
> > When skb is translated, transaction_token inherited. If 2 skb are merged 
> > (the same places where I put net_get_page's in my patch), the *older* 
> > token is inherited. This is the main point of this idea.
> >
> > Before starting new asynchronous send a client would open a new token. 
> > Everything sent then would receive that token. Finish_callback() would 
> > be called and the corresponding token freed, when io_count == 0 *AND* 
> > all previous tokens closed.
> >
> > This idea seems to be simpler, than even what Rusty implemented. Correct 
> > me, if I wrong. But, unfortunately, in the near future I will have no 
> > time to develop it.. :-(
>
> Yes, it is simpler and cleaner, but it requires additional allocation.
> This is additional (and quite noticeble) overhead.

Not necessary requires. For instance, in iscsi-scst sk_transaction_token 
can (and should) be part of iSCSI cmd structure, so no additional 
allocations would be needed.

Thanks,
Vlad


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/