From: Jack Steiner <steiner@sgi.com>
To: "Luck, Tony" <tony.luck@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
Mike Travis <travis@sgi.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
"isimatu.yasuaki@jp.fujitsu.com" <isimatu.yasuaki@jp.fujitsu.com>,
"kaneshige.kenji@jp.fujitsu.com" <kaneshige.kenji@jp.fujitsu.com>
Subject: Re: [PATCH 0/8] git pull request for tip/tracing/core
Date: Wed, 11 Feb 2009 14:39:55 -0600 [thread overview]
Message-ID: <20090211203954.GA9137@sgi.com> (raw)
In-Reply-To: <57C9024A16AD2D4C97DC78E552063EA361689C3B@orsmsx505.amr.corp.intel.com>
On Wed, Feb 11, 2009 at 09:57:00AM -0800, Luck, Tony wrote:
> > > Before we go and make the change, Peter brought up a good point on IRC. Is
> > > there any reason that ia64 needs 1 << 14 IRQs? That's 16384!
> > >
> > > Perhaps the better solution wolud be (if possible), to simply lower the
> > > number of bits.
> >
> > i'm the wrong person to be asked about that. (Cc:-ed the right people)
>
> People build some pretty big systems on ia64. SGI's largest has 4096
> cpus ... so 16384 IRQs is only 4 per cpu. That doesn't sound like very
> many to me.
As long as per-cpu interrupts (ex., timer, cpe_hndlr, cmc_hndlr, etc) are not counted
in the IRQ count, SGI is ok with 256 IRQs. We had problems overflowing the old
limit of 256 but have worked around it.
If per-cpu interrupts ARE counted in the total IRQs, then we currently use 5
per-cpu interrupts for each cpu. A 4k cpu config will need 20k IRQs + additional
IRQs for real devices.
I know the IRQ infrastructure has changed recently so this may no longer apply.
--- jack
next prev parent reply other threads:[~2009-02-11 20:40 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-08 5:49 [PATCH 0/8] git pull request for tip/tracing/core Steven Rostedt
2009-02-08 5:49 ` [PATCH 1/8] trace: remove deprecated entry->cpu Steven Rostedt
2009-02-08 12:29 ` Frederic Weisbecker
2009-02-08 5:49 ` [PATCH 2/8] ring-buffer: add NMI protection for spinlocks Steven Rostedt
2009-02-08 5:49 ` [PATCH 3/8] ring-buffer: allow tracing_off to be used in core kernel code Steven Rostedt
2009-02-08 5:49 ` [PATCH 4/8] ftrace, x86: rename in_nmi variable Steven Rostedt
2009-02-08 5:50 ` [PATCH 5/8] nmi: add generic nmi tracking state Steven Rostedt
2009-02-08 5:50 ` [PATCH 6/8] ftrace: change function graph tracer to use new in_nmi Steven Rostedt
2009-02-08 5:50 ` [PATCH 7/8] ring-buffer: use generic version of in_nmi Steven Rostedt
2009-02-08 5:50 ` [PATCH 8/8] trace: trivial fixes in comment typos Steven Rostedt
2009-02-09 9:37 ` [PATCH 0/8] git pull request for tip/tracing/core Ingo Molnar
2009-02-11 15:36 ` Ingo Molnar
2009-02-11 15:46 ` Steven Rostedt
2009-02-11 16:25 ` Ingo Molnar
2009-02-11 16:33 ` Steven Rostedt
2009-02-11 16:49 ` Steven Rostedt
2009-02-11 16:59 ` Steven Rostedt
2009-02-11 17:16 ` Ingo Molnar
2009-02-11 17:30 ` Steven Rostedt
2009-02-11 17:31 ` Ingo Molnar
2009-02-11 17:57 ` Luck, Tony
2009-02-11 18:23 ` Steven Rostedt
2009-02-11 18:34 ` Luck, Tony
2009-02-11 18:42 ` Steven Rostedt
2009-02-11 20:20 ` Ingo Molnar
2009-02-11 20:39 ` Jack Steiner [this message]
2009-02-12 2:39 ` Kenji Kaneshige
2009-02-12 2:43 ` Steven Rostedt
2009-02-12 3:15 ` Kenji Kaneshige
2009-02-12 3:22 ` Steven Rostedt
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