linux-kernel - Re: [PATCH] x86: skip delays during SMP initialization similar to Xen

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Date:	Tue, 12 May 2015 12:12:38 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Len Brown <lenb@...nel.org>,
	Jan H. Schönherr <jschoenh@...zon.de>,
	Thomas Gleixner <tglx@...utronix.de>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Anthony Liguori <aliguori@...zon.com>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Tim Deegan <tim@....org>,
	Gang Wei <gang.wei@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [PATCH] x86: skip delays during SMP initialization similar to Xen

On Tue, May 12, 2015 at 11:47:09AM +0200, Ingo Molnar wrote:
> So I was booting 120 CPUs with kvmtool (tools/kvm/ under -tip).
> 
> Even with your patches applied it's 7 seconds (config attached):
> 
> [    0.152189] x86: Booting SMP configuration:
> [    0.152705] .... node  #0, CPUs:          #1   #2   #3   #4   #5   #6   #7   #8   #9  #10  #11  #12  #13  #14  #15  #16  #17  #18  #19  #20  #21  #22  #23  #24  #25  #26  #27  #28  #29  #30  #31  #32  #33  #34  #35  #36  #37  #38  #39  #40  #41  #42  #43  #44  #45  #46  #47  #48  #49  #50  #51  #52  #53  #54  #55  #56  #57  #58  #59  #60  #61  #62  #63  #64  #65  #66  #67  #68  #69  #70  #71  #72  #73  #74  #75  #76  #77  #78  #79  #80  #81  #82  #83  #84  #85  #86  #87  #88  #89  #90  #91  #92  #93  #94  #95  #96  #97  #98  #99 #100 #101 #102 #103 #104 #105 #106 #107 #108 #109 #110 #111 #112 #113 #114 #115 #116 #117 #118 #119
> [    7.627192] x86: Booted up 1 node, 120 CPUs
> [    7.627795] smpboot: Total of 120 processors activated (672119.13 BogoMIPS)
> [    7.633325] devtmpfs: initialized
> 
> so there's some other delay going on. It could very well be a kvmtool 
> related initialization delay?

10 seconds with qemu+kvm and latest tip/master:

[    0.176297] x86: Booting SMP configuration:
[    0.179640] .... node  #0, CPUs:          #1   #2   #3   #4   #5   #6   #7   #8   #9  #10  #11  #12  #13  #14  #15  #16  #17  #18  #19  #20  #21  #22  #23  #24  #25  #26  #27  #28  #29  #30  #31  #32  #33  #34  #35  #36  #37  #38  #39  #40  #41  #42  #43  #44  #45  #46  #47  #48  #49  #50  #51  #52  #53  #54  #55  #56  #57  #58  #59  #60  #61  #62  #63  #64
[    0.036000] ------------[ cut here ]------------
[    0.036000] WARNING: CPU: 64 PID: 0 at kernel/locking/lockdep.c:2755 lockdep_trace_alloc+0x10c/0x120()
[    0.036000] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))
[    0.036000] Modules linked in:
[    0.036000] CPU: 64 PID: 0 Comm: swapper/64 Not tainted 4.1.0-rc3+ #6
[    0.036000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
[    0.036000]  ffffffff818c0f15 ffff88006d357d08 ffffffff8168c89b 0000000000000000
[    0.036000]  ffff88006d357d58 ffff88006d357d48 ffffffff81057d55 ffff88006d357da8
[    0.036000]  0000000000000080 0000000000000046 ffffffff81a4fb80 ffff88006d0af020
[    0.036000] Call Trace:
[    0.036000]  [<ffffffff8168c89b>] dump_stack+0x4f/0x7b
[    0.036000]  [<ffffffff81057d55>] warn_slowpath_common+0x95/0xe0
[    0.036000]  [<ffffffff81057de6>] warn_slowpath_fmt+0x46/0x50
[    0.036000]  [<ffffffff810a6d8c>] lockdep_trace_alloc+0x10c/0x120
[    0.036000]  [<ffffffff8113c82d>] __alloc_pages_nodemask+0xad/0xa20
[    0.036000]  [<ffffffff81691550>] ? mutex_lock_nested+0x2d0/0x3f0
[    0.036000]  [<ffffffff8132e2b3>] ? __this_cpu_preempt_check+0x13/0x20
[    0.036000]  [<ffffffff810a21ab>] ? trace_hardirqs_off_caller+0xcb/0x170
[    0.036000]  [<ffffffff81691524>] ? mutex_lock_nested+0x2a4/0x3f0
[    0.036000]  [<ffffffff8100a426>] ? init_espfix_ap.part.5+0xb6/0x270
[    0.036000]  [<ffffffff81096aea>] ? update_max_interval+0x1a/0x40
[    0.036000]  [<ffffffff8113d1bd>] __get_free_pages+0x1d/0x60
[    0.036000]  [<ffffffff8100a4d4>] init_espfix_ap.part.5+0x164/0x270
[    0.036000]  [<ffffffff8100a601>] init_espfix_ap+0x21/0x30
[    0.036000]  [<ffffffff8103c708>] start_secondary+0xe8/0x180
[    0.036000] ---[ end trace 2312a8d05943a0d2 ]---
[    5.744137]   #65  #66  #67  #68  #69  #70  #71  #72  #73  #74  #75  #76  #77  #78  #79  #80  #81  #82  #83  #84  #85  #86  #87  #88  #89  #90  #91  #92  #93  #94  #95  #96  #97  #98  #99 #100 #101 #102 #103 #104 #105 #106 #107 #108 #109 #110 #111 #112 #113 #114 #115 #116 #117 #118 #119
[   10.416459] x86: Booted up 1 node, 120 CPUs
[   10.420012] smpboot: Total of 120 processors activated (963228.36 BogoMIPS)

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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