Re: [Qemu-devel] [RFC PATCH V3 1/4] colo-compare: introduce colo compare initlization

[Zhang Chen <zhangchen.fnst@cn.fujitsu.com>]

On 05/12/2016 04:01 PM, Jason Wang wrote:
>
>
> On 2016年05月12日 14:49, Zhang Chen wrote:
>>
>>
>> On 05/09/2016 06:49 PM, Zhang Chen wrote:
>>>
>>>> +
>>>> +    s->chr_sec_in = qemu_chr_find(s->sec_indev);
>>>> +    if (s->chr_sec_in == NULL) {
>>>> +        error_setg(errp, "Secondary IN Device '%s' not found",
>>>> +                   s->sec_indev);
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    s->chr_out = qemu_chr_find(s->outdev);
>>>> +    if (s->chr_out == NULL) {
>>>> +        error_setg(errp, "OUT Device '%s' not found", s->outdev);
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    qemu_chr_fe_claim_no_fail(s->chr_pri_in);
>>>> +    qemu_chr_add_handlers(s->chr_pri_in, compare_chr_can_read,
>>>> +                          compare_pri_chr_in, NULL, s);
>>>> +
>>>> +    qemu_chr_fe_claim_no_fail(s->chr_sec_in);
>>>> +    qemu_chr_add_handlers(s->chr_sec_in, compare_chr_can_read,
>>>> +                          compare_sec_chr_in, NULL, s);
>>>> +
>>>>>>>>>> Btw, what's the reason of handling this in main loop? I 
>>>>>>>>>> thought it
>>>>>>>>>> would
>>>>>>>>>> be better to do this in colo thread? Otherwise, you need lots of
>>>>>>>>>> extra
>>>>>>>>>> synchronizations?
>>>>>>>>> Do you mean we should start/stop/do checkpoint it by colo-frame?
>>>>>>>> I mean we probably want to handle pri_in and sec_in in colo 
>>>>>>>> compare
>>>>>>>> thread. Through this way, there's no need for extra 
>>>>>>>> synchronization
>>>>>>>> with
>>>>>>>> main loop.
>>>>>>> I get your point, but how to do this.
>>>>>>> Now, we use qemu_chr_add_handlers to do this job.
>>>>>> You probably want to start a new main loop in colo comparing thread.
>>>>>
>>>>> IIUC, do you mean
>>>>> - remove char device read_handler
>>>>>
>>>>>   ↓at colo comparing thread↓
>>>>> while (true) {
>>>>> - blocking read packet from char device with select(2)/poll(2)...
>>>>> - compare packet
>>>>> }
>>>> Yes, something like this.
>>>>
>>>
>>> But remove qemu_chr_add_handlers I can't get fd to select/poll.
>>>
>>> How to get fd from all kinds of chardev?
>>>
>>
>> Hi~ jason.
>>
>> If we use chardev socket the fd save in QIOChannelSocket.
>>
>> and if we use chardev file the fd save in QIOChannelFile.
>>
>> Have any common method to get fd?
>
> I'm not sure I get the question. But you probably can call 
> qemu_chr_add_handlers() in colo comparing thread to solve this I think?
>

I have tested call qemu_chr_add_handlers() in colo comparing thread, but 
when data come,
the handler always running in main loop.

Thanks
Zhang Chen

>>
>>> Thanks
>>> Zhang Chen
>>>
>>>>> This solution will lead comparing packet and reading packet in 
>>>>> serial.
>>>>> But i don't know if this will have a good performance.
>>>> This probably won't have the best performance but it simplify lots of
>>>> things. Actually doing it in main loop will slow down all other I/O
>>>> processing. Consider colo can only handling userspace network traffic
>>>> now, we could start from this. For performance, it needs lots of other
>>>> stuff: I think the most important thing is to add vhost support.
>>>>
>>>> Thanks
>>>>
>>>>>>> Thanks
>>>>>>> zhangchen
>>>>>>
>>>>>> .
>>>>>>
>>>>
>>>>
>>>> .
>>>>
>>>
>>
>
>
>
> .
>

-- 
Thanks
zhangchen