From: Ashok Raj <ashok.raj@intel.com>
To: Andrew Morton <akpm@osdl.org>
Cc: Ashok Raj <ashok.raj@intel.com>,
olel@ans.pl, venkatesh.pallipadi@intel.com,
linux-kernel@vger.kernel.org, suresh.b.siddha@intel.com,
rajesh.shah@intel.com, ak@muc.de
Subject: Re: More than 8 CPUs detected and CONFIG_X86_PC cannot handle it on 2.6.16-rc6
Date: Mon, 13 Mar 2006 15:04:35 -0800 [thread overview]
Message-ID: <20060313150435.A26689@unix-os.sc.intel.com> (raw)
In-Reply-To: <20060313142223.7ac20a65.akpm@osdl.org>; from akpm@osdl.org on Mon, Mar 13, 2006 at 02:22:23PM -0800
On Mon, Mar 13, 2006 at 02:22:23PM -0800, Andrew Morton wrote:
> > 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_PC
> > ---help---
> > Say Y here to experiment with turning CPUs off and on. CPUs
> > can be controlled through /sys/devices/system/cpu.
>
> Longer term, it appears that we need to do some Kconfig and C work to
> separate out the HOTPLUG_CPU infrastructure which swsusp needs from actual
> CPU hotplugging.
The needs are not any different. Both (swsusp and cpu hotplug) both require
logical cpu offlining which is what CONFIG_HOTPLUG_CPU does.
Physical cpu hotplug is enabled by CONFIG_ACPI_HOTPLUG_CPU.
>
> What _is_ this IPI problem anyway? Can't send point-to-point IPIs to
> offlined CPUs? (Don't do that then?) Or do broadcast IPIs go wrong, or
> what?
Its not the point-to-point..we do that only to wake a CPU, but thats done
in flat physical mode always.
When we do smp_call_function() under X86_PC we use logical flat mode.
This sends a broadcast IPI by using a shortcut message. This is bad, since
the offline cpu may also receive it and process just when we bring the cpu
online.
send_IPI_allbutself() and send_IPI_all() versions that use the shortcut
values are the ones to avoid.
>
> And does it affect pretend-x86-hotplug, or is it only affecting real hotplug?
>
its no more pretend-x86, in the past we used to put the cpu in idle(),
now we do put the cpu in halt and bring back by another startup ipi, just like
boot sequence, both for x86 and x86_64.
--
Cheers,
Ashok Raj
- Open Source Technology Center
next prev parent reply other threads:[~2006-03-13 23:05 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
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 [this message]
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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