Re: lockf in installworld -- not a good idea

On Fri, Sep 29, 2006 at 10:20:53PM +0400, Ruslan Ermilov wrote:
> On Fri, Sep 29, 2006 at 11:09:42AM -0600, M. Warner Losh wrote:
> [...]
> > I tend to agree with that basic philosophy.  From other items in the
> > thread, it was clear this came up in the context of build release,
> > which benefits from -j usually.  The installworld phase in that should
> > be as robust as possible as well, since otherwise we have issues with
> > the actual release.  Unless it is a big win (more than a few percent),
> > I'd imagine the right fix is to the release target to not do a
> > parallel installworld.  I know that in the build scripts that I wrote
> > in 3.x days and have ported forward since then I've never done a
> > parallel install, due to it rarely working reliably in that (long)
> > time span...
> > 
> They are safe to do nowadays.  I'll do some measurements on real
> SMP with the memory-based DESTDIR, and let you know the numbers.
> 
The data (real time seconds) was taken on the following system:

CPU: AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ (1995.01-MHz K8-class CPU)
real memory  = 4227792896 (4031 MB)
avail memory = 4081033216 (3891 MB)
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs

Basically, doing installworld -jX doesn't make any sense.

: x installworld-B
: + installworld-j1
: +--------------------------------------------------------------------------+
: |xxx                                                               + +    +|
: ||A|                                                               |_MA___||
: +--------------------------------------------------------------------------+
:     N           Min           Max        Median           Avg        Stddev
: x   3         40.21         40.82         40.53         40.52    0.30512293
: +   3         56.72         58.45         57.26     57.476667    0.88511769
: Difference at 95.0% confidence
: 	16.9567 +/- 1.50052
: 	41.8476% +/- 3.70317%
: 	(Student's t, pooled s = 0.662017)

: x installworld-B
: + installworld-j2
: +--------------------------------------------------------------------------+
: |xx x                                                            +    +   +|
: ||A_|                                                            |___AM___||
: +--------------------------------------------------------------------------+
:     N           Min           Max        Median           Avg        Stddev
: x   3         40.21         40.82         40.53         40.52    0.30512293
: +   3         55.17         57.29         56.44          56.3     1.0669114
: Difference at 95.0% confidence
: 	15.78 +/- 1.77852
: 	38.9437% +/- 4.38924%
: 	(Student's t, pooled s = 0.784666)

: x installworld-B
: + installworld-j4
: +--------------------------------------------------------------------------+
: |xxx                                                         +        +  + |
: ||A|                                                          |_____A_M___||
: +--------------------------------------------------------------------------+
:     N           Min           Max        Median           Avg        Stddev
: x   3         40.21         40.82         40.53         40.52    0.30512293
: +   3         59.44         63.28         62.18     61.633333     1.9775068
: Difference at 95.0% confidence
: 	21.1133 +/- 3.2069
: 	52.106% +/- 7.91437%
: 	(Student's t, pooled s = 1.41486)


Cheers,
-- 
Ruslan Ermilov
ru_at_FreeBSD.org
FreeBSD committer