Sleep and Wake up

[greg@kroah.com (Greg KH)]

On Mon, May 02, 2011 at 02:02:34PM -0700, Abu Rasheda wrote:
> On Mon, May 2, 2011 at 12:28 PM, Greg KH <greg@kroah.com> wrote:
> > On Mon, May 02, 2011 at 11:32:32AM -0700, Abu Rasheda wrote:
> >> I am testing my driver on much faster host processor and facing
> >> following issues:
> >>
> >> My host is too powerful and it can fill up device buffer queue very fast.
> >
> > What kind of device is this?
> 
> its a networking device

It sounds like a broken device, you need to be able to handle large data
streams, right?  Are you running Linux in this device and that is the
issue you are having?

> >> I get best performance when I do busy wait, but this is not desirable
> >> and is bad design.
> >>
> >> I need to sleep and wake up quickly and predictability. Indication
> >> from device that queue has space, is coming in form of memory write
> >> (device writes to a memory location of i86 processor).
> >>
> >> I tried using wait_event_interruptible_timeout, I am depending on 2nd
> >> parameter of the function but it wake up is too slow, even tried using
> >> value of 1.
> >
> > Why not try increasing the buffer in your driver to handle any amount of
> > data needed?
> 
> Problem come from the fact that remote end can be slow, so device /
> driver cannot do much. If I increase buffer size, than running on
> (even) faster host processor will bring back same issue. I am looking
> for solution which will scale.
> 
> I check for available buffer size if space is low, I sleep and retry.
> This is causing lot of CPU to be wasted.
> 
> How can I optimize this ?

Use NAPI for your network driver?

good luck,

greg k-h