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From: Jens Axboe <jens.axboe@oracle.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org, Alan.Brunelle@hp.com,
	arjan@linux.intel.com, dgc@sgi.com, npiggin@suse.de
Subject: Re: [PATCH 4/8] x86: add support for remotely triggering the block  softirq
Date: Thu, 7 Feb 2008 11:17:28 +0100	[thread overview]
Message-ID: <20080207101727.GE15220@kernel.dk> (raw)
In-Reply-To: <20080207100738.GB7716@elte.hu>

On Thu, Feb 07 2008, Ingo Molnar wrote:
> 
> * Jens Axboe <jens.axboe@oracle.com> wrote:
> 
> > Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
> > ---
> >  arch/x86/kernel/smp_32.c                   |   15 +++++++++++++++
> >  arch/x86/kernel/smpboot_32.c               |    3 +++
> >  include/asm-x86/hw_irq_32.h                |    1 +
> >  include/asm-x86/mach-default/entry_arch.h  |    1 +
> >  include/asm-x86/mach-default/irq_vectors.h |    1 +
> >  5 files changed, 21 insertions(+), 0 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/smp_32.c b/arch/x86/kernel/smp_32.c
> > index dc0cde9..668b8a4 100644
> > --- a/arch/x86/kernel/smp_32.c
> > +++ b/arch/x86/kernel/smp_32.c
> > @@ -672,6 +672,21 @@ void smp_call_function_interrupt(struct pt_regs *regs)
> >  	}
> >  }
> >  
> > +fastcall void smp_raise_block_softirq(struct pt_regs *regs)
> 
> small detail: there's no fastcall used in arch/x86 anymore.

Yeah, andrew already complained about that, fixed up.

> > +{
> > +	unsigned long flags;
> > +
> > +	ack_APIC_irq();
> > +	local_irq_save(flags);
> > +	raise_softirq_irqoff(BLOCK_SOFTIRQ);
> > +	local_irq_restore(flags);
> > +}
> 
> if then this should be a general facility to trigger any softirq - not 
> just the block one.

Oh yeah, definitely agree, I wrote that in the intro as well. The
interface is horrible, not meant to go anywhere, just serve for testing.

> >  #define CALL_FUNCTION_VECTOR	0xfb
> > +#define BLOCK_SOFTIRQ_VECTOR	0xfa
> 
> this wastes another irq vector and is very special-purpose. Why not make 
> the smp_call_function() one more scalable instead?

That's definitely a possibility, Nick had something like that. I just
didn't like having to allocate a cookie object to store the function and
data.

> 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.

-- 
Jens Axboe


  reply	other threads:[~2008-02-07 10:17 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-07  9:18 [PATCH 0/8] IO queuing and complete affinity Jens Axboe
2008-02-07  9:18 ` [PATCH 1/8] block: split softirq handling into blk-softirq.c Jens Axboe
2008-02-07  9:18 ` [PATCH 2/8] Add interface for queuing work on a specific CPU Jens Axboe
2008-02-07  9:45   ` Andrew Morton
2008-02-07  9:49     ` Jens Axboe
2008-02-07 17:44       ` Harvey Harrison
2008-02-11 10:51     ` Oleg Nesterov
2008-02-07  9:19 ` [PATCH 3/8] block: make kblockd_schedule_work() take the queue as parameter Jens Axboe
2008-02-07  9:19 ` [PATCH 4/8] x86: add support for remotely triggering the block softirq Jens Axboe
2008-02-07 10:07   ` Ingo Molnar
2008-02-07 10:17     ` Jens Axboe [this message]
2008-02-07 10:25       ` Ingo Molnar
2008-02-07 10:31         ` Jens Axboe
2008-02-07 10:38           ` Ingo Molnar
2008-02-07 14:18             ` Jens Axboe
2008-02-07 10:49           ` [patch] block layer: kmemcheck fixes Ingo Molnar
2008-02-07 17:42             ` Linus Torvalds
2008-02-07 17:55               ` Jens Axboe
2008-02-07 19:31               ` Ingo Molnar
2008-02-07 20:06                 ` Jens Axboe
2008-02-08  1:22               ` David Miller
2008-02-08  1:28                 ` Linus Torvalds
2008-02-08 15:09                 ` Arjan van de Ven
2008-02-08 22:44                   ` Nick Piggin
2008-02-08 22:56                     ` Arjan van de Ven
2008-02-08 23:58                       ` Nick Piggin
2008-02-08 11:38               ` Jens Axboe
2008-02-07  9:19 ` [PATCH 5/8] x86-64: add support for remotely triggering the block softirq Jens Axboe
2008-02-07  9:19 ` [PATCH 6/8] ia64: " Jens Axboe
2008-02-07  9:19 ` [PATCH 7/8] kernel: add generic softirq interface for triggering a remote softirq Jens Axboe
2008-02-07  9:19 ` [PATCH 8/8] block: add test code for testing CPU affinity Jens Axboe
2008-02-07 15:16 ` [PATCH 0/8] IO queuing and complete affinity Alan D. Brunelle
2008-02-07 18:25 ` IO queuing and complete affinity with threads (was Re: [PATCH 0/8] IO queuing and complete affinity) Jens Axboe
2008-02-07 20:40   ` Alan D. Brunelle
2008-02-08  7:38   ` Nick Piggin
2008-02-08  7:47     ` Jens Axboe
2008-02-08  7:53       ` Nick Piggin
2008-02-08  7:59         ` Jens Axboe
2008-02-08  8:12           ` Nick Piggin
2008-02-08  8:24             ` Jens Axboe
2008-02-08  8:33               ` Nick Piggin
2008-02-11  5:22           ` David Chinner
2008-02-12  8:28             ` Jeremy Higdon

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