Re: Periodic rant about SCHED_ULE

On Mar 22, 2023, at 16:17, Mark Millard <marklmi@yahoo.com> wrote:

> On Mar 22, 2023, at 15:39, Mark Millard <marklmi@yahoo.com> wrote:
> 
>> On Mar 22, 2023, at 13:34, Mark Millard <marklmi@yahoo.com> wrote:
>> 
>>> On Mar 22, 2023, at 12:40, George Mitchell <george+freebsd@m5p.com> wrote:
>>> 
>>>> On 3/22/23 15:21, Mark Millard wrote:
>>>>> George Mitchell <george+freebsd@m5p.com> wrote on
>>>>> Date: Wed, 22 Mar 2023 17:36:39 UTC :
>>>>> [...]
>>>>>> Here are the very complicated instructions for reproducing the problem:
>>>>>> 1. Install and start misc/dnetc from ports.
>>>>> Installing is likely easy, as likely would be building
>>>>> with default options (if any). I know nothing about
>>>>> starting misc/dnetc so that is research. (Possibly
>>>>> trivial, although if it has alternatives to control
>>>>> then I'd need to match that context too.)
>>>> 
>>>> service dnetc start
>>> 
>>> I built and installed misc/dnetc and got a binary
>>> blob that clearly was not built in my environment:
>>> 
>>> # file /usr/local/distributed.net/dnetc
>>> /usr/local/distributed.net/dnetc: ELF 64-bit LSB executable, x86-64, version 1 (FreeBSD), statically linked, for FreeBSD 10.1 (1001515), FreeBSD-style, stripped
>>> 
>>> Way older FreeBSD vintage than the locally available toolchains
>>> would normally build. Some might be cautious about such a thing.
>>> 
>>> The man page reported that:
>>> 
>>> QUOTE
>>>   If you have never run the client before, it will initiate the menu-driven
>>>   configuration. Save and quit when done, the configuration file will be
>>>   saved in the same directory as the client. Now, simply restart the
>>>   client. From that point on it will use the saved configuration.
>>> END QUOTE
>>> 
>>> I've not seen what the configuration asks about yet.
>> 
>> I went through the configuration, basically just looking
>> at it, other than providing an E-mail address. Then . . .
>> 
>> $ sudo service dnetc start
>> Password:
>> Cannot 'start' dnetc. Set dnetc_enable to YES in /etc/rc.conf or use 'onestart' instead of 'start'.
>> 
>> $ sudo service dnetc onestart
>> 
>> I just let it run without any extra competing activity, other
>> than I had my patched version of top running. It records and
>> reports various maximum-observed (MaxObs) figures, here
>> the load averages being relevant.
>> 
>> Top showed that dnetc started 32 processes, one per hardware
>> thread. Mostly I saw: 100% nice and 0% idle.
>> 
>> Letting it run and then looking at the load averages (and
>> their matching MaxObs figures) after something like 60+ min
>> (not carefully timed: was doing other things) showed:
>> 
>> load averages:  31.97,  31.88,  31.66 MaxObs:  32.12,  31.97,  31.66
>> 
>> (Note: The machine had been up for over 2.75 days before
>> starting this and had not been building much of anything
>> during that time.)
>> 
>> I've not yet experimented with having other, significant
>> competing activity.
>> 
>>>>>> 2. Run "make buildworld".
>>>>> So on the 32 hardware-thread (16 cores) amd64 machine that
>>>>> I have access to, the test is to only have buildworld use
>>>>> about one hardware thread, no matter what else is going on.
>>>>> I never would have guessed that the steps would not involve
>>>>> more like -j$(sysctl -n hw.ncpu) (so around -j32 in this
>>>>> context). So it is good that you provided your note or
>>>>> I'd not know if I'd done similarly or not when trying such.
>>>>> [Note: -j1 and lack of -j are not strictly equivalent in
>>>>> how make operates. As I remember, the distinction makes
>>>>> a notable difference in the number of subprocesses created
>>>>> directly by make (one per action "line" vs. one for the
>>>>> whole block?). So even using -j1 might make a difference
>>>>> vs. what you specified. I'd have to test to see.]
>>>> 
>>>> I am literally running "make buildworld" with no additional options.
>>> 
>>> So required for repeating your results, but likely making
>>> such results not be interesting relative to how I normally
>>> deal with buildworld buildkernel and the likel, no matter
>>> if there is other activity in an overlapping time frame or
>>> not: my time preferences are too strong to wait for a single
>>> hardware thread to do my normal builds, even with no
>>> competing activity on the builder.
>>> 
>>>>>> Standard out conveniently reports how long it took (wall clock).
>>>>> But nothing in your instructions indicate about how
>>>>> to get an idea much progress dnetc made during the
>>>>> various tests? [...]
>>>> 
>>>> Honestly, I've never worried about this part.  But dnetc logs its
>>>> progress in /usr/local/distributed.net/dnetc.txt, though not in terms
>>>> that are easy to relate to real-world progress.  Oddly, when I run
>>>> "make buildworld," I'm primarily interested in getting the world built.
>>>> Perhaps others feel differently.
>>> 
>>> Off topic for the specifics of the actual benchmark
>>> that you run:
>>> 
>>> Then why not use of -jN ? In my context, any buildworld
>>> using -j1 or no -j at all takes a huge amount of time
>>> longer than letting it use all the hardware threads (or
>>> so). (I've avoided having any I/O bound contexts for
>>> such.) It does not take additional load on the system
>>> for that to be true --including on the 4-core small arm
>>> boards when I happen to buildworld on such (rare).
>>> 
>>> 
>>>>> [...]
>>>>> FYI: I've never built with and run the alternate
>>>>> scheduler so if there is any appropriate background
>>>>> for that that would not be obvious on finding basic
>>>>> instructions, it would be appropriate to provide
>>>>> such notes.
>>>>> [...]
>>>> 
>>>> You have to build a new kernel, using a config file in which you have
>>>> replaced "options SCHED_ULE" with "options SCHED_4BSD".     -- George
>>> 
>>> Thanks for the notes.
>>> 
>>> I've not decided if I'll do anything with the binary
>>> blob or not.
>> 
> 
> FYI:
> 
> It is not your specific experiment, but I started my
> "extra load" experimenst with . . .
> 
> I started a -j32 buildworld buildkernel with dnetc still
> running. I'm generally seeing around 55% Active and 42%

Note "Active": user, sorry.

> nice, < 2% system (it was building libllvm at this point).
> At that time:
> 
> load averages:  64.41,  60.52,  49.81 MaxObs:  64.47,  60.52,  49.81
> 

Contrasting results for some obj-lib32 build activity:
much more variety of User, nice, and system, including
times with < 5% user, 90+% nice. But not typical overall.
But lots of time roughly around 50%/50% or 35%/60%. There
were times with 15+% system.

Somewhat after buildkernel started:

load averages:  69.15,  64.12,  58.72 MaxObs:  75.98,  64.12,  58.72

Harder to summarize, so overall timing reports from the
buildworld and buildkernel stages.


buildworld:

--------------------------------------------------------------
... World build completed on Wed Mar 22 16:37:57 PDT 2023
... World built in 2615 seconds, ncpu: 32, make -j32
--------------------------------------------------------------


buildkernel:

--------------------------------------------------------------
... Kernel build for GENERIC-NODBG completed on Wed Mar 22 16:43:10 PDT 2023
--------------------------------------------------------------
... Kernel(s)  GENERIC-NODBG built in 311 seconds, ncpu: 32, make -j32
--------------------------------------------------------------

Afterwards:

load averages:  36.08,  53.14,  55.79 MaxObs:  75.98,  65.77,  59.84


I then did (not all in the same window):

$ sudo service dnetc onestop
# rm -fr /usr/obj/BUILDs/main-amd64-nodbg-clang-alt/usr/

before another -j32 buildworld buildkernel (no dnetc). The
reuslts for this were:


buildworld:

--------------------------------------------------------------
... World build completed on Wed Mar 22 17:39:19 PDT 2023
... World built in 1240 seconds, ncpu: 32, make -j32
--------------------------------------------------------------

(compared to the 2615 for dnetc also in use)


buildkernel:

--------------------------------------------------------------
... Kernel build for GENERIC-NODBG completed on Wed Mar 22 17:41:17 PDT 2023
--------------------------------------------------------------
... Kernel(s)  GENERIC-NODBG built in 118 seconds, ncpu: 32, make -j32
--------------------------------------------------------------

(compared to the 311 for dnetc also in use)


Experiments without -j32 will take a lot longer, even
without dnetc in use. I'm not sure there will be such
results today.



===
Mark Millard
marklmi at yahoo.com