linux-kernel - Re: [PATCH 4/8] x86: add support for remotely triggering the block softirq

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Date:	Thu, 7 Feb 2008 11:31:36 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, Alan.Brunelle@...com,
	arjan@...ux.intel.com, dgc@....com, npiggin@...e.de
Subject: Re: [PATCH 4/8] x86: add support for remotely triggering the block  softirq

On Thu, Feb 07 2008, Ingo Molnar wrote:
> 
> * Jens Axboe <jens.axboe@...cle.com> wrote:
> 
> > > on the more conceptual level, shouldnt we just move to threads 
> > > instead of softirqs? That way you can become affine to any CPU and 
> > > can do cross-CPU wakeups anytime - which will be nice and fast via 
> > > the smp_reschedule_interrupt() facility.
> > 
> > That would indeed be nicer and not require any arch changes. I was 
> > afraid it would be more costly than massaging the softirqs a bit 
> > though, perhaps that is unfounded.
> 
> pick up the threaded softirq patches from -rt, those move all softirqs 
> processing into kernel threads. I'd suggest to extend those via 
> wakeup-from-remote functionality - it fits the construct quite 
> naturally. You should also be able to directly observe any performance 
> impact of threaded softirq handlers. (and if you find any, let me know 
> so that we can make it faster :-)

I was just considering that, since I knew -rt moved the softirqs into
threads. I'll look into it, but may not post anything until after my
vacation.

-- 
Jens Axboe

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