From: Ashok Raj <ashok.raj@intel.com>
To: Andrew Morton <akpm@osdl.org>
Cc: Krzysztof Oledzki <olel@ans.pl>,
venkatesh.pallipadi@intel.com, linux-kernel@vger.kernel.org,
ashok.raj@intel.com, suresh.b.siddha@intel.com,
rajesh.shah@intel.com
Subject: Re: More than 8 CPUs detected and CONFIG_X86_PC cannot handle it on 2.6.16-rc6
Date: Mon, 13 Mar 2006 11:36:15 -0800 [thread overview]
Message-ID: <20060313113615.A24797@unix-os.sc.intel.com> (raw)
In-Reply-To: <20060312143053.530ef6c9.akpm@osdl.org>; from akpm@osdl.org on Sun, Mar 12, 2006 at 02:30:53PM -0800
On Sun, Mar 12, 2006 at 02:30:53PM -0800, Andrew Morton wrote:
>
> Maybe we should have:
>
> if (num_possible_cpus() <= 8)
> dont_do_any_of_that_stuff();
>
> That's assuming that hotplug-cpu-capable platforms are correctly setting
> cpu_possible_map. Do they?
That wont work, since we use HOTPLUG_CPU to suspend/resume as well. We
switched to using bigsmp (that uses physflat for IPI's) just to avoid
sending IPI's to offline CPUs. When we use logical flat we use shortcuts
that have ill effects on CPUs that are offline.
Think making CONFIG_HOTPLUG_CPU depend on X86_GENERICARCH, or X86_BIGSMP
seems like a better choice.
--
Cheers,
Ashok Raj
- Open Source Technology Center
When CONFIG_HOTPLUG_CPU is turned on we always use physflat mode (bigsmp) even
when #of CPUs are less than 8 to avoid sending IPI to offline processors.
Without having BIGSMP on it spits out a warning during boot on systems that
seems misleading, since it complains even on systems that have less
than 8 cpus.
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
---------------------------------------------------------
arch/i386/Kconfig | 2 +-
1 files changed, 1 insertion(+), 1 deletion(-)
Index: linux-2.6.16-rc6-mm1/arch/i386/Kconfig
===================================================================
--- linux-2.6.16-rc6-mm1.orig/arch/i386/Kconfig
+++ linux-2.6.16-rc6-mm1/arch/i386/Kconfig
@@ -760,7 +760,7 @@ config PHYSICAL_START
config HOTPLUG_CPU
bool "Support for hot-pluggable CPUs (EXPERIMENTAL)"
- depends on SMP && HOTPLUG && EXPERIMENTAL && !X86_VOYAGER
+ depends on SMP && HOTPLUG && EXPERIMENTAL && !X86_VOYAGER && (X86_GENERICARCH || X86_BIGSMP)
---help---
Say Y here to experiment with turning CPUs off and on. CPUs
can be controlled through /sys/devices/system/cpu.
next prev parent reply other threads:[~2006-03-13 19:36 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-12 2:04 More than 8 CPUs detected and CONFIG_X86_PC cannot handle it on 2.6.16-rc6 Krzysztof Oledzki
2006-03-12 5:03 ` Andrew Morton
2006-03-12 11:04 ` Krzysztof Oledzki
2006-03-12 11:25 ` Andrew Morton
2006-03-12 13:05 ` Krzysztof Oledzki
2006-03-12 15:35 ` Venkatesh Pallipadi
2006-03-12 21:13 ` Krzysztof Oledzki
2006-03-12 22:30 ` Andrew Morton
2006-03-13 19:36 ` Ashok Raj [this message]
2006-03-13 19:51 ` Andrew Morton
2006-03-13 20:05 ` Ashok Raj
2006-03-13 22:22 ` Andrew Morton
2006-03-13 23:04 ` Ashok Raj
2006-03-15 5:44 ` Nathan Lynch
2006-03-15 6:18 ` Shaohua Li
2006-03-15 7:31 ` Andrew Morton
2006-03-15 9:37 ` [PATCH] No need to protect current->group_info in sys_getgroups(), in_group_p() and in_egroup_p() Eric Dumazet
2006-03-20 19:09 ` [PATCH] Use unsigned int types for a faster bsearch Eric Dumazet
2006-03-22 5:06 ` [PATCH] Use __read_mostly on some hot fs variables Eric Dumazet
2006-03-22 5:15 ` Nick Piggin
2006-03-22 6:23 ` [RFC, PATCH] avoid some atomics in open()/close() for monothreaded processes Eric Dumazet
2006-03-22 6:41 ` Andrew Morton
2006-03-22 6:59 ` Eric Dumazet
2006-03-22 7:03 ` Andrew Morton
2006-03-15 18:09 ` More than 8 CPUs detected and CONFIG_X86_PC cannot handle it on 2.6.16-rc6 Ashok Raj
-- strict thread matches above, loose matches on Subject: below --
2006-03-15 10:50 Chuck Ebbert
2006-03-15 15:44 ` Krzysztof Oledzki
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