Re: Collapsing RT signals ...

From: Dan Kegel (
Date: Sun Jun 24 2001 - 23:21:57 EST

Davide Libenzi <> wrote:
> I'm making some test with RT signals and looking at how they're implemented
> inside the kernel.
> After having experienced frequent queue overflow signals I looked at how
> signals are queued inside the task_struct.
> There's no signals optimization inside and this make the queue length depending
> on the request rate instead of the number of connections.
> It can happen that two ( or more ) POLL_IN signals are queued with a single
> read() that sweep the buffer leaving other signals to issue reads ( read this
> as user-mode / kernel-mode switch ) that will fail due lack of data.
> So for every "superfluous" signal we'll have two user-mode / kernel-mode
> switches, one for signal delivery and one for a failing read().
> I'm just thinking at a way to optimize the signal delivery that is ( draft ) :
> ...

I agree, the queue overflow case is a pain in the butt.

Before you get too far coding up your idea, have you read
? He's already implemented and benchmarked a variation on this
idea, maybe you could vet his code. He has taken it a step
further than perhaps you were going to.

(See also )

- Dan
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