linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Ingo Molnar <mingo@kernel.org>
To: Josh Boyer <jwboyer@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	prarit@redhat.com, x86@kernel.org, linux-kernel@vger.kernel.org,
	Russ Anderson <rja@sgi.com>
Subject: [PATCH v2 2/2] x86: Increase MAXSMP CPU count to 8192
Date: Wed, 6 Nov 2013 06:56:34 +0100	[thread overview]
Message-ID: <20131106055634.GA24044@gmail.com> (raw)
In-Reply-To: <20131105143816.GK9944@hansolo.jdub.homelinux.org>


* Josh Boyer <jwboyer@redhat.com> wrote:

> The MAXSMP option is intended to enable silly large numbers of CPUs for
> testing purposes.  The current value of 4096 isn't very silly any longer
> as there are actual machines that approach 6096 CPUs when taking HT into
> account.  Increase the value to 8192 to account for this and short term
> future increases.
> 
> Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
> ---
>  arch/x86/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index f03e428..09f05cd 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -828,7 +828,7 @@ config NR_CPUS
>  	range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK
>  	range 2 4096 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
>  	default "1" if !SMP
> -	default "4096" if MAXSMP
> +	default "8192" if MAXSMP

So I changed the patch to up the regular range to 8192 as well: it's more 
consistent if MAXSMP tracks the normal range, as long as the defaults are 
sane. See the commit below.

Note that 'normal users' won't ever see any max CPU count beyond the 
current 512 (which is already kind of crazy for normal use), because 
CPUMASK_OFFSTACK is turned off on all but MAXSMP configs (unless the
user explicitly enables the option).

So it's not really possible to accidentally wander into that option and 
set it to an insane value - it takes some effort.

[ I've Cc:-ed Linus, who had a strong opinion about these max-cpu limits
  in the past - I hope the changes are fine in this form. ]

Thanks,

	Ingo

=====================>
>From 07bce9fd69e8409740e63db0ab0755b84ee61a0c Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer@redhat.com>
Date: Tue, 5 Nov 2013 09:38:16 -0500
Subject: [PATCH] x86/cpu: Increase max CPU count to 8192

The MAXSMP option is intended to enable silly large numbers of
CPUs for testing purposes.  The current value of 4096 isn't very
silly any longer as there are actual SGI machines that approach
6096 CPUs when taking HT into account.

Increase the value to a nice round 8192 to account for this and
allow for short term future increases.

Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Cc: prarit@redhat.com
Cc: Russ Anderson <rja@sgi.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20131105143816.GK9944@hansolo.jdub.homelinux.org
[ Tweaked it so that MAXSMP simply sets the maximum of the normal range. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/Kconfig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f03e428..805469a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -826,9 +826,9 @@ config NR_CPUS
 	int "Maximum number of CPUs" if SMP && !MAXSMP
 	range 2 8 if SMP && X86_32 && !X86_BIGSMP
 	range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK
-	range 2 4096 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
+	range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
 	default "1" if !SMP
-	default "4096" if MAXSMP
+	default "8192" if MAXSMP
 	default "32" if SMP && (X86_NUMAQ || X86_SUMMIT || X86_BIGSMP || X86_ES7000)
 	default "8" if SMP
 	---help---

  reply	other threads:[~2013-11-06  5:56 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-11-01 14:11 [PATCH] x86: Allow NR_CPUS=1024 Josh Boyer
2013-11-03 10:18 ` Ingo Molnar
2013-11-03 10:21   ` Ingo Molnar
2013-11-03 15:57     ` Josh Boyer
2013-11-03 17:43       ` H. Peter Anvin
2013-11-04  6:51         ` Ingo Molnar
2013-11-04 16:31           ` H. Peter Anvin
2013-11-04  6:53       ` Ingo Molnar
2013-11-04 14:01         ` Josh Boyer
2013-11-04 14:10           ` Ingo Molnar
2013-11-04 14:16             ` Josh Boyer
2013-11-04 14:54               ` Prarit Bhargava
2013-11-04 15:56               ` Russ Anderson
2013-11-04 17:48                 ` Ingo Molnar
2013-11-04 19:08                   ` H. Peter Anvin
2013-11-04 20:11                     ` Ingo Molnar
2013-11-04 22:50                       ` H. Peter Anvin
2013-11-05  6:25                         ` Ingo Molnar
2013-11-05  6:31                           ` Li Zefan
2013-11-03 14:29   ` Prarit Bhargava
2013-11-03 14:42     ` Russ Anderson
2013-11-05 14:37 ` [PATCH 1/2 v2] x86: Allow higher NR_CPUS values Josh Boyer
2013-11-05 14:38   ` [PATCH 2/2] x86: Increase MAXSMP CPU count to 8192 Josh Boyer
2013-11-06  5:56     ` Ingo Molnar [this message]
2013-11-06 14:10       ` [PATCH v2 " Josh Boyer
2013-11-06 11:20     ` [tip:x86/cpu] x86/cpu: Increase max " tip-bot for Josh Boyer
2013-11-06  7:15   ` [PATCH 1/2 v2] x86: Allow higher NR_CPUS values Ingo Molnar
2013-11-06 14:12     ` Josh Boyer
2013-11-06 15:04       ` Josh Boyer
2013-11-06 15:21     ` [PATCH v3] x86/cpu: " Josh Boyer
2013-11-07  9:15       ` Ingo Molnar
2013-11-07 13:51         ` Josh Boyer
2013-11-06 11:20   ` [tip:x86/cpu] " tip-bot for Josh Boyer

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20131106055634.GA24044@gmail.com \
    --to=mingo@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=hpa@zytor.com \
    --cc=jwboyer@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=prarit@redhat.com \
    --cc=rja@sgi.com \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH v2 2/2] x86: Increase MAXSMP CPU count to 8192' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).