Messages in this thread | | | Date | Tue, 18 Dec 2001 09:16:48 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: Scheduler ( was: Just a second ) ... |
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On Tue, 18 Dec 2001, Roger Larsson wrote: > > Lets see: we have >1 GHz CPU and interrupts at >1000 Hz > => 1 Mcycle / interrupt - is that insane?
Ehh.. First off, the CPU may be 1GHz, but the memory subsystem, and the PCI subsystem definitely are _not_. Most PCI cards still run at a (comparatively) leisurely 33MHz, and when we're talking about audio, we're talking about actually having to _access_ that audio device.
Yes. At 33MHz, not at 1GHz.
Also, at 32-byte fragments, the frequency is actually 5.5kHz, not 1kHz. Now, I seriously doubt the mp3-player actually used 32-byte fragments (it probably just asked for something small, and got it), but let's say it asked for something in the kHz range (ie 256-512 byte frags). That does _not_ equate to "1 Mcycle". It equates to 33 _kilocycles_ in PCI-land, and a PCI read will take several cycles.
> If the hardware can support it? Why not let it? It is really up to the > applications/user to decide...
Well, this particular user was unhappy with the CPU spending a noticeably amount of time on just web-surfing and mp3-playing.
So clearly the _user_ didn't ask for it.
And I suspect that the app writer just didn't even realize what he did. He may have used another sound card that didn't even allow small fragments.
Linus
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