Re: Testers wanted: dracut lazy install with cpio

[John Reiser <jreiser-Po6cBsTGB2ZWk0Htik3J/w@public.gmane.org>]

On 02/28/2012 09:46 AM, David Dillow wrote:

> I tend to agree that the ~2 second improvements reported so far are not
> compelling, but I see those as the developers case. I'm more interested
> in the users' case -- is that 14 seconds Cong reported real?

I suspect that the 14 seconds difference was between a cold cache (first run)
and a warm cache (third run).  There wasn't anything non-real about it,
but the cache effect was much larger than the lazy/non-lazy algorithm.
The measurements that I reported yesterday were all warm-cache cases,
and I saw much closer improvement in wall-clock time (several percent)
for lazy, in both testimage and hostimage.  This is consistent with
the hypothesis that the improvement was due to the lazy case using one
(or a small handful) cpio of many files at a time, versus the non-lazy
case doing one /bin/cp for each file.  The savings is in reduced
usage of fork[clone]+execve+ld_linux.so+wait.

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