Re: Any idea about what makes Emacs slow reading on pipes?

[Jan D.]

> Here is a more elaborate test file
> <testio.el>
> If I run this and print out test-pattern afterwards, I get
>
> test-pattern
...

> And from then on (actually backwards in time) only packets with single
> characters, with perhaps 100 filter calls per second.

I think this is a scheduling issue.  After all, dd is only reading one
character at a time.  I do get some one character reads, but not many.
There is more one character reads on a RedHat 6 than on the Mandrake 9,
not because of some difference in the systems, but because the RedHat
runs on a much slower machine (AMD K6 450Mhz versus AMD Athlon 1400).

For example, if I change to dd bs=1024 count=100, I get no single 
character
reads at all.  If I raise the priority of dd, I get 1024 consistently 
even
on the slower machine.

        Jan D.