13 Jul
2005
13 Jul
'05
3:01 p.m.
On Wed, 2005-07-13 at 10:49 -0400, Eric Dantan Rzewnicki wrote:
On Tue, Jul 12, 2005 at 07:34:07PM -0400, Lee Revell
wrote:
Saving battery on laptops. The only performance numbers anyone posted
indicated HZ=250 sped up a kernel compile on a 16 CPU machine (!) by
~5%, and this was after the fact. Not exactly compelling...
But since Linus and Andrew apparently all use laptops, us desktop people
are screwed...
Lee
On Wed, 2005-07-13 at 01:03 +0200, Florian
Schmidt wrote:
What is driving the kernel-devs to regress on this issue?
Some semieducated blabbering ahead (might be all
wrong):
I think i once read that interrupt handling "short circuits" the linux
scheduler (in the sense that not only at every timer interrupt but also
at the end of finishing any interrupt handler the kernel looks which
processes are ready to run etc. and maybe there's a high prio process
waiting just for that interrupt (by i.e. polling or reading on a device
file).
So for all those realtime processes that depend on events that are
triggering interrupts (like soundcards' irqs) the timer interrupt really
doesn't matter. I'm not sure at all though this applies to midi handling
(and especially to alsa_seq when routing from one app to another) or is
even correct in any sense at all :)
Anyone can shed light?
Correct, it's not an issue for apps driven by hardware
interrupts like
JACK, because the sound card consumes data at a constant rate. But for
MIDI or video where you have to periodically push data to the device it
matters.