command piped into bzip not using all available CPU

[Jim C. Nasby]

decibel at fritz.1[9:34]~:6>uname -a
FreeBSD fritz.distributed.net 5.2.1-RELEASE FreeBSD 5.2.1-RELEASE #1:
Wed Apr  7 18:42:52 CDT 2004
root at fritz.distributed.net:/usr/obj/usr/src/sys/FRITZ  amd64

decibel at fritz.1[9:35]/usr/src/sys/amd64/conf:9>grep -i sched FRITZ 
options         SCHED_4BSD              #4BSD scheduler
options         _KPOSIX_PRIORITY_SCHEDULING #Posix P1003_1B real-time extensions

Also, don't read anything into the fact that they were on the same CPU
for that snapshot; here's one showing the exact opposite:

  PID USERNAME PRI NICE   SIZE    RES STATE  C   TIME   WCPU    CPU COMMAND
10336 dnetc    139   20  1344K   856K RUN    1  80.5H 90.14% 90.14% dnetc
10702 decibel  108    0 10856K  7304K CPU0   1   0:13 23.86% 22.41% bzip2
10703 pgsql      4    0   154M 78004K sbwait 0   0:07 10.92% 10.25% postgres


FWIW, I recall seeing this same behavior under FreeBSD 4.x as well.

On Mon, Apr 19, 2004 at 11:27:16PM -0400, Scott Lambert wrote:
> On Mon, Apr 19, 2004 at 09:09:21AM -0500, Jim C. Nasby wrote:
> > Why would I expect to see it only use one CPU? It was CPU bound, not
> > disk bound. There were two CPU-intensive processes running, why wouldn't
> > they each use a different CPU?
> > 
> > On Mon, Apr 19, 2004 at 12:08:32AM -0700, Aaron Seelye wrote:
> > > I'm not sure the exact technical reason, but as I understand that, it's
> > > 47% idle on the total cpu power of the machine, which would indicate
> > > that one cpu was 100% full, and the other was 3%, due to system usage,
> > > i/o, or whatever else was running.  This is quite normal in my
> > > experience, and what you should expect to see.
> 
> At the time you took the snapshot, both processes were running on the
> same CPU.  FreeBSD 4.x or 5.2?  If 5.2, SCHED_4BSD or SCHED_ULE?
> 
> > > > The command I'm running is:
> > > > pg_dump -vZ0 ogr | bzip2 > ogr-20040416.sql.bz2
> > > >
> > > >   PID USERNAME PRI NICE   SIZE    RES STATE  C   TIME   WCPU    CPU COMMAND
> > > > 17334 decibel  109    0 10856K  7164K CPU0   0  11:05 65.77% 65.77% bzip2
> > > > 17335 pgsql      4    0   154M   124M sbwait 0   5:54 34.03% 34.03% postgres
> > > > 17333 decibel   -8    0 20128K  3236K pipdwt 0   0:46  2.88%  2.88% pg_dump
> 
> -- 
> Scott Lambert                    KC5MLE                       Unix SysAdmin
> lambert at lambertfam.org
> 
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-- 
Jim C. Nasby, Database Consultant                  jim at nasby.net
Member: Triangle Fraternity, Sports Car Club of America
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