Re: [PATCH v3 3/7] support UFFD write fault processing in ram_save_iterate()

[Peter Xu]

On Fri, Nov 20, 2020 at 07:15:07PM +0300, Andrey Gruzdev wrote:
> Yeah, I think we can re-use the postcopy queue code for faulting pages. I'm
> worring a little about some additional overhead dealing with urgent request
> semaphore. Also, the code won't change a lot, something like:
> 
> [...]
>         /* In case of 'write-tracking' migration we first try
>          * to poll UFFD and sse if we have write page fault event */
>         poll_fault_page(rs);
> 
>         again = true;
>         found = get_queued_page(rs, &pss);
> 
>         if (!found) {
>             /* priority queue empty, so just search for something dirty */
>             found = find_dirty_block(rs, &pss, &again);
>         }
> [...]

Could I ask what's the "urgent request semaphore"?  Thanks,

-- 
Peter Xu