From: "H. Peter Anvin" <hpa@zytor.com>
To: Mike Travis <travis@sgi.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
davej@codemonkey.org.uk, David Miller <davem@davemloft.net>,
Eric Dumazet <dada1@cosmosbay.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Jack Steiner <steiner@sgi.com>,
Jeremy Fitzhardinge <jeremy@goop.org>, Jes Sorensen <jes@sgi.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org,
Christoph Lameter <cl@linux-foundation.org>,
Andi Kleen <andi@firstfloor.org>
Subject: Re: [RFC] CPUMASK: proposal for replacing cpumask_t
Date: Fri, 12 Sep 2008 15:58:14 -0700 [thread overview]
Message-ID: <48CAF406.5030607@zytor.com> (raw)
In-Reply-To: <48CAF249.2050304@sgi.com>
Mike Travis wrote:
>
> Here's the thread:
>
> http://marc.info/?l=linux-kernel&m=121976977901223&w=4
>
> It doesn't seem worthwhile to force all systems to deal with large cpumask's
> if they don't need to. Passing the value on the stack (actually usually in a
> reg) if it fits into a long makes a lot of sense.
>
> And I don't think it's that abstract, but I'm willing to hear other opinions.
>
> Btw, most likely only distros that distribute an "Enterprise" edition of
> Linux will ever set NR_CPUS so high, so the actual number of systems making
> use of this will be a very small percentage (big $$-wise though... ;-)
>
> I even think that perhaps BITS_PER_LONG might be too low a threshold to kick
> in this extra code. A Larabee chip will have 128 cpus so maybe 128 or 256 is
> a better metric...?
>
> As soon as I get a working kernel with the proposed changes, I will definitely
> be doing perf testing.
>
If the performance difference isn't significant, then there is a major
advantage to getting rid of a configuration option. At that point we
can basically scale to an arbitrary number of processors in a stock
configuration.
-hpa
next prev parent reply other threads:[~2008-09-12 23:05 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-06 23:50 [RFC 00/13] smp: reduce stack requirements for genapic send_IPI_mask functions Mike Travis
2008-09-06 23:50 ` [RFC 01/13] smp: modify send_IPI_mask interface to accept cpumask_t pointers Mike Travis
2008-09-06 23:50 ` [RFC 02/13] cpumask: add for_each_online_cpu_mask_nr function Mike Travis
2008-09-06 23:50 ` [RFC 03/13] xen: use new " Mike Travis
2008-09-06 23:50 ` [RFC 04/13] cpumask: add cpumask_ptr operations Mike Travis
2008-09-06 23:50 ` [RFC 05/13] cpumask: add get_cpumask_var debug operations Mike Travis
2008-09-06 23:50 ` [RFC 06/13] genapic: use get_cpumask_var operations for allbutself cpumask_ts Mike Travis
2008-09-06 23:50 ` [RFC 07/13] sched: Reduce stack size requirements in kernel/sched.c Mike Travis
2008-09-07 10:24 ` Peter Zijlstra
2008-09-07 11:00 ` Andrew Morton
2008-09-07 13:05 ` Peter Zijlstra
2008-09-08 14:56 ` Mike Travis
2008-09-07 20:28 ` Peter Zijlstra
2008-09-08 14:54 ` Mike Travis
2008-09-08 15:05 ` Peter Zijlstra
2008-09-08 18:38 ` Ingo Molnar
2008-09-10 22:47 ` [RFC] CPUMASK: proposal for replacing cpumask_t Mike Travis
2008-09-10 22:53 ` Andi Kleen
2008-09-10 23:33 ` Mike Travis
2008-09-11 5:21 ` Andi Kleen
2008-09-11 9:00 ` Peter Zijlstra
2008-09-11 15:04 ` Mike Travis
2008-09-12 4:55 ` Rusty Russell
2008-09-12 14:28 ` Mike Travis
2008-09-12 22:02 ` Rusty Russell
2008-09-12 22:50 ` Mike Travis
2008-09-12 22:58 ` H. Peter Anvin [this message]
2008-09-06 23:50 ` [RFC 08/13] cpufreq: Reduce stack size requirements in acpi-cpufreq.c Mike Travis
2008-09-06 23:50 ` [RFC 09/13] genapic: reduce stack pressuge in io_apic.c step 1 temp cpumask_ts Mike Travis
2008-09-08 11:01 ` Andi Kleen
2008-09-08 16:03 ` Mike Travis
2008-09-06 23:50 ` [RFC 10/13] genapic: reduce stack pressuge in io_apic.c step 2 internal abi Mike Travis
2008-09-06 23:50 ` [RFC 11/13] genapic: reduce stack pressuge in io_apic.c step 3 target_cpus Mike Travis
2008-09-07 7:55 ` Bert Wesarg
2008-09-07 9:13 ` Ingo Molnar
2008-09-08 15:01 ` Mike Travis
2008-09-08 15:29 ` Mike Travis
2008-09-06 23:50 ` [RFC 12/13] genapic: reduce stack pressuge in io_apic.c step 4 vector allocation Mike Travis
2008-09-06 23:50 ` [RFC 13/13] genapic: reduce stack pressuge in io_apic.c step 5 cpu_mask_to_apicid Mike Travis
2008-09-07 7:36 ` [RFC 00/13] smp: reduce stack requirements for genapic send_IPI_mask functions Ingo Molnar
2008-09-08 15:17 ` Mike Travis
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