Re: kern/51615: Userland processes not evenly distributed on all CPUs

[Hubert Feyrer <hubert%feyrer.de@localhost>]

The following reply was made to PR kern/51615; it has been noted by GNATS.

From: Hubert Feyrer <hubert%feyrer.de@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: Hubert Feyrer <hubert%feyrer.de@localhost>
Subject: Re: kern/51615: Userland processes not evenly distributed on all
 CPUs
Date: Sun, 13 Nov 2016 01:20:22 +0100 (CET)

 Update:
 
 I have learned that this PR is a duplicate of PR 43561,
 funny enough the patch proposed there was the same as here,
 though implemented lightly different.
 
 Following an advice to test it, I did so:
 
 I've started a "build.sh -j8" on a (VMware Fusion) VM with 4 CPUs on a
 Macbook Pro, and it nearly brought the machine to a halt - What I saw was
 lots of idle time on all CPUs though. I aborted the exercise to get some
 CPU cycles for me back.
 
 I restarted the exercise with 2 CPUs in the same VM, and there I saw load
 distribution on both CPUs (not much wonder with -j8), but there was also
 quite some idle times in the 'make clean / install' phases that I'm not
 sure is normal. During the actual build phases I wasn't able to see idle
 time, though the system spent quite some time in the kernel (system).
 Example top(1) output is appended below.
 
 All in all, I'd say the patch is a good step forward from the current
 situation, which does not properly distribute pure CPU hogs, at all.
 
 
   - Hubert
 
 
 load averages:  9.01,  8.60,  7.15;               up 0+01:24:11      01:19:33
 67 processes: 7 runnable, 58 sleeping, 2 on CPU
 CPU0 states:  0.0% user, 55.4% nice, 44.6% system,  0.0% interrupt,  0.0% idle
 CPU1 states:  0.0% user, 69.3% nice, 30.7% system,  0.0% interrupt,  0.0% idle
 Memory: 311M Act, 99M Inact, 6736K Wired, 23M Exec, 322M File, 395M Free
 Swap: 1536M Total, 21M Used, 1516M Free
 
    PID USERNAME PRI NICE   SIZE   RES STATE      TIME   WCPU    CPU COMMAND
 27028 feyrer    20    5    62M   27M CPU/1      0:00  9.74%  0.93% cc1
    728 feyrer    85    0    78M 3808K select/1   1:03  0.73%  0.73% sshd
 23274 feyrer    21    5    36M   14M RUN/0      0:00 10.00%  0.49% cc1
 21634 feyrer    20    5    44M   20M RUN/0      0:00  7.00%  0.34% cc1
 24697 feyrer    77    5  7988K 2480K select/1   0:00  0.31%  0.15% nbmake
 24964 feyrer    74    5    11M 5496K select/1   0:00  0.44%  0.15% nbmake
 18221 feyrer    21    5    49M   15M RUN/0      0:00  2.00%  0.10% cc1
 14513 feyrer    20    5    43M   16M RUN/0      0:00  2.00%  0.10% cc1
    518 feyrer    43    0    15M 1764K CPU/0      0:02  0.00%  0.00% top
 20842 feyrer    21    5  6992K  340K RUN/0      0:00  0.00%  0.00% x86_64--netb
 16215 feyrer    21    5    28M  172K RUN/0      0:00  0.00%  0.00% cc1
   8922 feyrer    20    5    51M   14M RUN/0      0:00  0.00%  0.00% cc1