Sleep and Wake up

[Abu Rasheda]

On Mon, May 2, 2011 at 12:28 PM, Greg KH <greg at 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

>> 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 ?

>
> thanks,
>
> greg k-h