Doug Barton wrote:
> Oliver Fromme wrote:
> > In this case, the "real" time is much larger than the
> > "user" time. I guess that's the overhead of 85677 files
> > and 23399 directories (according to find(1)). :-)
>
> Did you perform your tests once only with each method, and one right
> after the other? If so, the effect you saw might be due to file system
> caching.
I performed each test several times in succession. If the
first run was much different from the rest, I ignored it,
so the caches were filled the same on all runs.
But 100,000 files still cause some I/O overhead, even if
the data is cached and the I/O requests don't actually hit
the physical disks.
Anyway, my point is not about caching and I/O. The numbers
are pretty normal in that regard. My point is about the
difference in CPU ("user") time when using "tar -cz" vs.
"tar -c | gzip".
Meanwhile I had a quick look at the code: gzip uses some
optimized assembler code (for x86 and 680x0), while libz
doesn't have such a thing. Maybe that's the reason why
gzip is noticeably faster.
Best regards
Oliver
--
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd
Any opinions expressed in this message may be personal to the author
and may not necessarily reflect the opinions of secnetix in any way.
"The last good thing written in C was
Franz Schubert's Symphony number 9."
-- Erwin Dieterich
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