From: Suresh Siddha <suresh.b.siddha@intel.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
Paul McKenney <paul.mckenney@us.ibm.com>
Subject: Re: [PATCH v2] x86: don't ever patch back to UP if we unplug cpus.
Date: Mon, 30 Jul 2012 10:09:53 -0700 [thread overview]
Message-ID: <1343668193.3696.574.camel@sbsiddha-desk.sc.intel.com> (raw)
In-Reply-To: <874noqm21b.fsf@rustcorp.com.au>
On Mon, 2012-07-30 at 11:40 +0930, Rusty Russell wrote:
> We still patch SMP instructions to UP variants if we boot with a
> single CPU, but not at any other time. In particular, not if we
> unplug CPUs to return to a single cpu.
>
> Paul McKenney points out:
>
> mean offline overhead is 6251/48=130.2 milliseconds.
>
> If I remove the alternatives_smp_switch() from the offline
> path [...] the mean offline overhead is 550/42=13.1 milliseconds
>
> Basically, we're never going to get those 120ms back, and the code is
> pretty messy.
>
> We get rid of:
> 1) The "smp-alt-once" boot option. It's actually "smp-alt-boot", the
> documentation is wrong. It's now the default.
> 2) The skip_smp_alternatives flag used by suspend.
> 3) arch_disable_nonboot_cpus_begin() and arch_disable_nonboot_cpus_end()
> which were only used to set this one flag.
>
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
next prev parent reply other threads:[~2012-07-30 17:06 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-27 7:38 [PATCH] " Rusty Russell
2012-07-27 20:28 ` Suresh Siddha
2012-07-30 1:15 ` Rusty Russell
2012-07-30 2:10 ` [PATCH v2] " Rusty Russell
2012-07-30 17:09 ` Suresh Siddha [this message]
2012-08-22 9:41 ` Ingo Molnar
2012-08-23 6:27 ` Rusty Russell
2012-07-30 2:08 ` [PATCH] " Rusty Russell
2012-08-02 8:23 ` Ingo Molnar
2012-08-06 7:59 ` [PATCH fixed for !SMP] " Rusty Russell
2012-08-22 10:20 ` [tip:x86/asm] x86/smp: Don' t " tip-bot for Rusty Russell
2012-08-23 10:53 ` tip-bot for Rusty Russell
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