Re: [PATCH v3 1/1] oslib-posix: initialize backend memory objects in parallel

[David Hildenbrand <david@redhat.com>]

On 31.01.24 15:48, Mark Kanda wrote:
> On 1/31/24 8:30 AM, David Hildenbrand wrote:
>>>
>>> OK. I'll call it 'PHASE_LATE_BACKENDS_CREATED' (to make it consistent
>>> with code comments/function name).
>>
>> But then, you should set it at the very end of the function (not sure
>> if that would be a problem with the other devices that are getting
>> created in between -- if they would be using one of these memory
>> backends; likely not).
>>
> 
> I think I misunderstood your suggestion. I was planning to add it a
> 'phase_advance(PHASE_LATE_BACKENDS_CREATED)' to qemu_init():
> 
>      @@ -3703,6 +3703,7 @@ void qemu_init(int argc, char **argv)
>             * over memory-backend-file objects).
>             */
>            qemu_create_late_backends();
>      +    phase_advance(PHASE_LATE_BACKENDS_CREATED);
> 
> And use PHASE_LATE_BACKENDS_CREATED (instead of
> PHASE_MACHINE_INITIALIZED) for the async bool in
> host_memory_backend_memory_complete().
> 
> I was planning to leave this call where it is:
> 
>      @@ -2009,6 +2009,14 @@ static void qemu_create_late_backends(void)
> 
>            object_option_foreach_add(object_create_late);
> 
>      +    /*
>      +     * Wait for any outstanding memory prealloc from created memory
>      +     * backends to complete.
>      +     */
>      +    if (!qemu_finish_async_mem_prealloc(&error_fatal)) {
>      +        exit(1);
>      +    }
>      +
>            if (tpm_init() < 0) {
>                exit(1);
>            }
> 

Yes. The only "suboptimal" things is that if someone where to create a 
memory backend between qemu_finish_async_mem_prealloc() and 
phase_advance(PHASE_LATE_BACKENDS_CREATED), it would never get preallocated.

That likely won't ever happen by any of the remaining stuff in 
qemu_create_late_backends(), especially not with "prealloc=on" and 
thread-contexts set.

-- 
Cheers,

David / dhildenb