Re: Don't Understand wait() and notify()

Patricia Shanahan <>
Thu, 29 Mar 2007 07:19:45 -0700
SadRed wrote:

On Mar 29, 5:53 pm, Patricia Shanahan <> wrote:

SadRed wrote:

On Mar 29, 1:31 pm, Patricia Shanahan <> wrote:

SadRed wrote:

On Mar 29, 1:03 pm, Patricia Shanahan <> wrote:

SadRed wrote:
...> (Local file system access can't be but sequential. So, multi-

threading on
   them is futile, though.)

Why must local file system access be sequential?

Oh sorry. I didn't know that you use a multi-head hard disk device!

You still seem to be implying that local file system access is limited
to one device. I've worked with systems that had dozens of disk drives.
However, even if there is only one disk head, getting multiple I/O's
issued can enable disk head movement optimization. If the I/Os are
issued one at a time, the drive has to do them in that order, which is
not necessarily an efficient order.
I've worked with systems that had dozens of disk drives.

And they had supported parallel I/Os. How gorgeous!

I was one of the developers of the Sun E10000. With up to 64 processors,
we needed far higher I/O bandwidth and transaction rate than we could
have got out of a single I/O path. I don't think we ever even thought
about sequential local file system access as a design option.


Wow 64 pocessors! Good. You are an elite and we are not. We are not
talking about your level of system in every topic of public fora. You
even don't understand that but you should.

I'm afraid you are right that I don't understand the idea of separating
computing into "elite" and "non-elite" categories, with only the
"non-elite" considered fit for discussion in public fora.

Out of order execution was one of the special features of the CDC 6600,
presumably "elite". These days, it is normal in desktop processors.

RAID was originally a way of applying to servers the price/capacity of
mass produced disk drives, but the last time I saw a terabyte scale
RAID-5 disk array it was on the external disk drive shelf at a local
home electronics store.

A few years ago someone who divided computing into "elite" and
"non-elite" might have classed parallelizing compute bound work as an
"elite" technique, because, of course, no computer one should talk about
in public fora could possibly really run more than one thread at a time.

My working assumption is that there are three possible states for an
"elite" computer performance idea: it is already on desktops, or it is
coming soon to a desktop near you, or it has been superseded by better


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