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

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

> +
> +    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?

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