From: Robin Holt <holt@sgi.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Robin Holt <holt@sgi.com>, Russ Anderson <rja@sgi.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Shawn Guo <shawn.guo@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [PATCH] Do not force shutdown/reboot to boot cpu.
Date: Wed, 10 Apr 2013 14:00:03 -0500 [thread overview]
Message-ID: <20130410190003.GH3658@sgi.com> (raw)
In-Reply-To: <20130410175519.GG3658@sgi.com>
> > I'm proposing to make 'reboot' overhead profilable, via a debug hack:
> >
> > echo 1 > /proc/sys/kernel/magic_dont_fully_reboot_flag
> >
> > perf record reboot
> >
> > perf is using NMIs to profile - and since much of cpu_down() is with irqs
> > disabled, NMI profiling would be needed to see inside the overhead.
> >
> > (Assuming the 240 msecs is CPU overhead, not waiting for some IRQ/IPI event.)
I had the machine booted as 512 cpus.
I tweaked the kernel like this:
diff --git a/kernel/sys.c b/kernel/sys.c
index 39c9c4a..b42bd4f 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -368,8 +368,10 @@ EXPORT_SYMBOL(unregister_reboot_notifier);
*/
void kernel_restart(char *cmd)
{
- kernel_restart_prepare(cmd);
+ // kernel_restart_prepare(cmd);
disable_nonboot_cpus();
+ enable_nonboot_cpus();
+ return;
if (!cmd)
printk(KERN_EMERG "Restarting system.\n");
else
perf record -a /sbin/reboot -d -f -n
The top of 'perf report' has:
Events: 14M cycles
22.58% swapper [kernel.kallsyms] [k] update_cfs_rq_blocked_load
10.52% swapper [kernel.kallsyms] [k] load_balance
4.96% swapper [kernel.kallsyms] [k] ktime_get
4.12% swapper [kernel.kallsyms] [k] update_blocked_averages
3.55% swapper [kernel.kallsyms] [k] idle_cpu
1.97% swapper [kernel.kallsyms] [k] uv_read_rtc
0.98% swapper [kernel.kallsyms] [k] rcu_process_gp_end
0.84% swapper [kernel.kallsyms] [k] apic_timer_interrupt
0.84% swapper [kernel.kallsyms] [k] __lock_text_start
0.84% swapper [kernel.kallsyms] [k] _raw_spin_lock_irqsave
0.73% swapper [kernel.kallsyms] [k] native_safe_halt
0.56% swapper [kernel.kallsyms] [k] rcu_check_callbacks
0.56% swapper [kernel.kallsyms] [k] native_write_msr_safe
0.44% swapper [kernel.kallsyms] [k] cpumask_next_and
0.42% reboot [kernel.kallsyms] [k] kmem_cache_alloc_node
The perf data is 676 MB. I don't know how well it compresses, but the
lzma task has been running for a while.
Thanks,
Robin
next prev parent reply other threads:[~2013-04-10 19:00 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-03 19:37 [PATCH] Do not force shutdown/reboot to boot cpu Robin Holt
2013-04-08 15:57 ` Ingo Molnar
2013-04-08 16:11 ` H. Peter Anvin
2013-04-08 16:59 ` Robin Holt
2013-04-10 11:16 ` Ingo Molnar
2013-04-10 14:01 ` Robin Holt
2013-04-10 15:10 ` Linus Torvalds
2013-04-10 15:29 ` Russ Anderson
2013-04-10 16:59 ` Ingo Molnar
2013-04-10 17:14 ` Robin Holt
2013-04-10 17:22 ` Ingo Molnar
2013-04-10 17:55 ` Robin Holt
2013-04-10 19:00 ` Robin Holt [this message]
2013-04-11 8:57 ` Ingo Molnar
2013-04-11 11:34 ` Robin Holt
2013-04-11 12:00 ` Ingo Molnar
2013-04-11 12:03 ` Robin Holt
2013-04-11 12:08 ` Robin Holt
2013-04-11 12:14 ` Ingo Molnar
2013-04-10 17:58 ` H. Peter Anvin
2013-04-10 23:02 ` Russ Anderson
2013-04-10 22:29 ` Russ Anderson
2013-04-11 5:31 ` Paul Mackerras
2013-04-11 12:45 ` Bulk CPU Hotplug (Was Re: [PATCH] Do not force shutdown/reboot to boot cpu.) Srivatsa S. Bhat
2013-04-11 13:48 ` Robin Holt
2013-04-12 5:37 ` Ingo Molnar
2013-04-12 6:09 ` Srivatsa S. Bhat
2013-04-12 9:31 ` Robin Holt
2013-04-12 10:01 ` Robin Holt
2013-04-13 16:30 ` Oleg Nesterov
2013-04-15 16:04 ` Robin Holt
2013-04-15 16:09 ` Oleg Nesterov
2013-04-15 16:10 ` Robin Holt
2013-04-13 17:01 ` Srivatsa S. Bhat
2013-04-15 10:16 ` Ingo Molnar
2013-04-15 12:02 ` Robin Holt
2013-04-15 15:59 ` Robin Holt
2013-04-16 9:40 ` Ingo Molnar
2013-04-11 14:23 ` Russ Anderson
2013-04-11 14:45 ` Srivatsa S. Bhat
2013-04-11 20:08 ` Russ Anderson
2013-04-11 20:17 ` Srivatsa S. Bhat
2013-04-11 21:08 ` Robin Holt
2013-04-08 16:54 ` [PATCH] Do not force shutdown/reboot to boot cpu Robin Holt
2013-04-08 17:07 ` Russ Anderson
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