On 6 February 2010 c. 17:53:09 Otto Moerbeek wrote:
quoted text
> On Sat, Feb 06, 2010 at 09:14:53AM -0500, Ted Unangst wrote:
> > On Sat, Feb 6, 2010 at 8:44 AM, Mark Kettenis
<mark.kettenis@xs4all.nl> wrote:
quoted text
> > >> > Continuing in my "make IO suck less" phase, cp would be a lot
> > >> > more efficient if it didn't bounce the disk heads around so
> > >> > much. ?Instead of using a tiny 64k buffer, use an amount based
> > >> > on a small fraction of RAM.
> > >>
> > >> Isn't it the task of the buffer cache to optimize memory use
> > >> here?
> > >
> > > Exactly the point I was just about to raise.
> >
> > Optimizing memory has nothing to do with it.  The buffer cache
> > doesn't do a whole lot to reduce seeking.  This is what cp looks
> > like:
> >
> > read .000001s
> > seek .001s
> > write .000001s
> > seek .001s
> > read .000001s
> > seek .001s
> >
> > It doesn't matter if the buffer cache does readahead, it never reads
> > enough ahead.  It doesn't matter if the buffer cache is write back,
> > the writes are still in the queue, and the elevator still goes.  If
> > you were moving from the 10th floor to the 90th floor, would you
> > take the boxes up one at a time?
>
> The buffer cache should ne smart enough to optmize read and writes in
> such large chunks so that the seeking gets reduced. The problem with
> your big buffers is that you are claiming resources even if you have
> no idea if they are available or not.
>
> 	-Otto

I have a cool idea about super-duper-mega-knob.

Let's choose and use globally a new environment variable, say,
LIVEFASTDIEYOUNG. If it's not defined, or empty, then current, sane
defaults will be used in programs; otherwise, programs should go
searching the shortest way to strike yourself in the foot.

Then each program you want can be modified to depend on it:

    const char *lfdy = getenv("LIVEFASTDIEYOUNG");
    if (lfdy != NULL && *lfdy != '\0') {
        // Do some crazy things
    } else {
        // Sane as usual
    }

Or this could be an sysctl, so even kernel flow can be modified. Yes,
it'll produce more bloat, but who cares? ;)

--
  Best wishes,
    Vadim Zhukov

A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?


P.S.: Didn't want to hurt anyone. Really.