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Date: Tue, 5 May 2009 12:48:13 +0930
From: Rusty Russell <rusty@...tcorp.com.au>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>, davem@...emloft.net,
netdev@...r.kernel.org
Subject: Re: [PATCH 0/3] tun: fix aio
On Mon, 27 Apr 2009 07:04:55 pm Michael S. Tsirkin wrote:
> On Mon, Apr 27, 2009 at 10:48:37AM +0930, Rusty Russell wrote:
> > > Sure. Here it is: much smaller, but slightly slower.
> >
> > Which could probably be fixed by using an on-stack version for a iovec
> > of less than a certain size...
>
> I agree that for large message sizes the malloc would probably be
> dwarfed by the cost of memory copy. However a large iovec might pass a
> small message, might it not?
Sorry, I didn't make myself clear. Something like:
struct iovec smalliov[512 / sizeof(struct iovec)];
if (count < ARRAY_SIZE(smalliov)) {
iv = smalliov;
} else {
iv = kmalloc(...)
}
...
if (iv != smalliov)
kfree(iv);
Cheers,
Rusty.
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