Re: [RFT][patch] Scheduling for HTT and not only

Hi,

[Sorry for the delay, I got a bit sidetrack'ed...]

2012/2/17 Alexander Motin <mav_at_freebsd.org>:
> On 17.02.2012 18:53, Arnaud Lacombe wrote:
>>
>> On Fri, Feb 17, 2012 at 11:29 AM, Alexander Motin<mav_at_freebsd.org>  wrote:
>>>
>>> On 02/15/12 21:54, Jeff Roberson wrote:
>>>>
>>>> On Wed, 15 Feb 2012, Alexander Motin wrote:
>>>>>
>>>>> I've decided to stop those cache black magic practices and focus on
>>>>> things that really exist in this world -- SMT and CPU load. I've
>>>>> dropped most of cache related things from the patch and made the rest
>>>>> of things more strict and predictable:
>>>>> http://people.freebsd.org/~mav/sched.htt34.patch
>>>>
>>>>
>>>> This looks great. I think there is value in considering the other
>>>> approach further but I would like to do this part first. It would be
>>>> nice to also add priority as a greater influence in the load balancing
>>>> as well.
>>>
>>>
>>> I haven't got good idea yet about balancing priorities, but I've
>>> rewritten
>>> balancer itself. As soon as sched_lowest() / sched_highest() are more
>>> intelligent now, they allowed to remove topology traversing from the
>>> balancer itself. That should fix double-swapping problem, allow to keep
>>> some
>>> affinity while moving threads and make balancing more fair. I did number
>>> of
>>> tests running 4, 8, 9 and 16 CPU-bound threads on 8 CPUs. With 4, 8 and
>>> 16
>>> threads everything is stationary as it should. With 9 threads I see
>>> regular
>>> and random load move between all 8 CPUs. Measurements on 5 minutes run
>>> show
>>> deviation of only about 5 seconds. It is the same deviation as I see
>>> caused
>>> by only scheduling of 16 threads on 8 cores without any balancing needed
>>> at
>>> all. So I believe this code works as it should.
>>>
>>> Here is the patch: http://people.freebsd.org/~mav/sched.htt40.patch
>>>
>>> I plan this to be a final patch of this series (more to come :)) and if
>>> there will be no problems or objections, I am going to commit it (except
>>> some debugging KTRs) in about ten days. So now it's a good time for
>>> reviews
>>> and testing. :)
>>>
>> is there a place where all the patches are available ?
>
>
> All my scheduler patches are cumulative, so all you need is only the last
> mentioned here sched.htt40.patch.
>
You may want to have a look to the result I collected in the
`runs/freebsd-experiments' branch of:

https://github.com/lacombar/hackbench/

and compare them with vanilla FreeBSD 9.0 and -CURRENT results
available in `runs/freebsd'. On the dual package platform, your patch
is not a definite win.

> But in some cases, especially for multi-socket systems, to let it show its
> best, you may want to apply additional patch from avg_at_ to better detect CPU
> topology:
> https://gitorious.org/~avg/freebsd/avgbsd/commit/6bca4a2e4854ea3fc275946a023db65c483cb9dd
>
test I conducted specifically for this patch did not showed much improvement...

 - Arnaud