lkml.org 
[lkml]   [2009]   [Sep]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: BFS vs. mainline scheduler benchmarks and measurements
On Wed, Sep 09 2009, Nikos Chantziaras wrote:
> On 09/09/2009 09:04 PM, Ingo Molnar wrote:
>> [...]
>> * Jens Axboe<jens.axboe@oracle.com> wrote:
>>
>>> On Wed, Sep 09 2009, Jens Axboe wrote:
>>> [...]
>>> BFS210 runs on the laptop (dual core intel core duo). With make -j4
>>> running, I clock the following latt -c8 'sleep 10' latencies:
>>>
>>> -rc9
>>>
>>> Max 17895 usec
>>> Avg 8028 usec
>>> Stdev 5948 usec
>>> Stdev mean 405 usec
>>>
>>> Max 17896 usec
>>> Avg 4951 usec
>>> Stdev 6278 usec
>>> Stdev mean 427 usec
>>>
>>> Max 17885 usec
>>> Avg 5526 usec
>>> Stdev 6819 usec
>>> Stdev mean 464 usec
>>>
>>> -rc9 + mike
>>>
>>> Max 6061 usec
>>> Avg 3797 usec
>>> Stdev 1726 usec
>>> Stdev mean 117 usec
>>>
>>> Max 5122 usec
>>> Avg 3958 usec
>>> Stdev 1697 usec
>>> Stdev mean 115 usec
>>>
>>> Max 6691 usec
>>> Avg 2130 usec
>>> Stdev 2165 usec
>>> Stdev mean 147 usec
>>
>> At least in my tests these latencies were mainly due to a bug in
>> latt.c - i've attached the fixed version.
>>
>> The other reason was wakeup batching. If you do this:
>>
>> echo 0> /proc/sys/kernel/sched_wakeup_granularity_ns
>>
>> ... then you can switch on insta-wakeups on -tip too.
>>
>> With a dual-core box and a make -j4 background job running, on
>> latest -tip i get the following latencies:
>>
>> $ ./latt -c8 sleep 30
>> Entries: 656 (clients=8)
>>
>> Averages:
>> ------------------------------
>> Max 158 usec
>> Avg 12 usec
>> Stdev 10 usec
>
> With your version of latt.c, I get these results with 2.6-tip vs
> 2.6.31-rc9-bfs:
>
>
> (mainline)
> Averages:
> ------------------------------
> Max 50 usec
> Avg 12 usec
> Stdev 3 usec
>
>
> (BFS)
> Averages:
> ------------------------------
> Max 474 usec
> Avg 11 usec
> Stdev 16 usec
>
>
> However, the interactivity problems still remain. Does that mean it's
> not a latency issue?

It probably just means that latt isn't a good measure of the problem.
Which isn't really too much of a surprise.

--
Jens Axboe



\
 
 \ /
  Last update: 2009-09-09 22:53    [from the cache]
©2003-2011 Jasper Spaans