Re: [PATCH] O10int for interactivity

[Nick Piggin <piggin@cyberone.com.au>]

Oliver Neukum wrote:

>>>This part interests me. It would seem that either 
>>>1. The AS scheduler should not bother waiting at all if the process is not 
>>>going to wake up in that time
>>>
>>How about something as simple as: if process sleeps, and AS scheduler
>>is waiting since last request from that process, AS scheduler stops
>>waiting immediately?
>>

No its fine if the process were to sleep on something. Its the
amount of time between IOs that is important (and is measured).
Makes no difference if the process is computing something or
waiting for something really.

>>
>>In other words, a hook in the process scheduler when a process goes to
>>sleep, to tell the AS scheduler to stop waiting.
>>
>>Although this would not always be optimal, for many cases the point of
>>AS is that the process is continuing to run, not sleeping, and will
>>issue another request shortly.
>>
>
>How do you tell which task dirtied the page?
>Wouldn't giving a bonus to tasks doing file io achieve the same purpose?
>Also, isn't quickly waking up tasks more important?
>

With AS, it doesn't matter what task created the IO, its what
task will have to wait on it. In the case of async writes, we
don't care about them anyway because the pagecache means they
get done a long way behind the instruction pointer of the
process anyway, so they'll be nicely layed out anyway.