Re: [Qemu-devel] [PATCH] rewrote timer implementation for rtl8139.

[Igor Kovalenko <igor.v.kovalenko@gmail.com>]

On Sat, Feb 20, 2010 at 2:26 AM, Anthony Liguori <anthony@codemonkey.ws> wrote:
> On 02/19/2010 04:22 PM, Alexander Graf wrote:
>>
>> On 19.02.2010, at 22:50, Anthony Liguori wrote:
>>
>>
>>>
>>> On 02/16/2010 02:35 AM, Frediano Ziglio wrote:
>>>
>>>>
>>>> Add a QEMU timer only when needed (timeout status not set, timeout
>>>> irq wanted and timer set).
>>>>
>>>> This patch is required for Darwin. Patch has been tested under
>>>> FreeBSD, Darwin and Linux.
>>>>
>>>> Signed-off-by: Frediano Ziglio<freddy77@gmail.com>
>>>>
>>>>
>>>
>>> Alex, I know you've played with this feature for OS X in the past.
>>>
>>> Is this something we should be enabling unconditionally?
>>>
>>
>> I've played with it and realized that
>>
>> 1) OSX's rtl8139 driver uses this timer instead of tx/rx interrupts to
>> process the queue
>> 2) it was broken
>>
>> I haven't gotten around to test if this patch makes it work, but I'd
>> suppose so.
>>
>> So yes, I think it should be enabled by default. It's a feature real hw
>> has, so we should emulate it.
>>
>
> The thing that concerns me is why it was disabled by default.  Igor, what
> was the reasoning for disabling it if you recall?

It was very inefficient pci timer implementation which fired callback
frequently.
Once it was found that (freebsd?) was relying on pci timer in realtek driver
to communicate we just added missing piece.

Now this patch fixes that inefficiency issue.

-- 
Kind regards,
Igor V. Kovalenko