TTY task group scheduling

[Daniel Nebdal]

On Fri, Nov 19, 2010 at 12:06 AM, Alexander Kabaev <kabaev at gmail.com> wrote:
> On Thu, 18 Nov 2010 18:56:35 +0000
> Alexander Best <arundel at freebsd.org> wrote:
>
>> On Thu Nov 18 10, Matthew D. Fuller wrote:
>> > On Thu, Nov 18, 2010 at 06:23:24PM +0000 I heard the voice of
>> > Alexander Best, and lo! it spake thus:
>> > >
>> > > judging from the videos the changes are having a huge impact imo.
>> >
>> > Well, my (admittedly limited, and certainly anecdotal) experience is
>> > that Linux's interactive response when under heavy load was always
>> > much worse than FreeBSD's.  So maybe that's just them catching up to
>> > where we already are   ;)
>>
>> well...i tried playing back a 1080p vide files while doing
>> `make -j64 buildkernel` and FreeBSD's interactivity seems far from
>> perfect.
>
> One thing that just begs to be asked: since when decoding 1080p became
> an interactive task?
>

Strictly speaking it isn't - but displaying it is a timing-sensitive
task that isn't CPU- or I/O-bound, and scheduling-wise that probably
makes it more like the "fast response when woken up" interactive tasks
than a CPU-bound non-interactive process.
Decoding it into another file on the disk is in the latter category,
of course - but I don't think that's what he meant. :)

More on topic - while this was a tiny patch for Linux, it seems like
it would take more work for us, since I don't believe either of the
schedulers handles task groups in the required way. The linux patch
was just "create task groups automatically", since they already had
some suitable logic for scheduling based on task groups in their CFS
scheduler. We would have to (re-)add that first, which is non-trivial.


--
Daniel Nebdal