From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Dario Faggioli <dario.faggioli@citrix.com>
Cc: Elena Ufimtseva <elena.ufimtseva@oracle.com>,
Wei Liu <wei.liu2@citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
David Vrabel <david.vrabel@citrix.com>,
Jan Beulich <JBeulich@suse.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Subject: Re: PV-vNUMA issue: topology is misinterpreted by the guest
Date: Tue, 21 Jul 2015 16:00:29 -0400 [thread overview]
Message-ID: <55AEA4DD.7080406@oracle.com> (raw)
In-Reply-To: <55AD08F7.7020105@oracle.com>
On 07/20/2015 10:43 AM, Boris Ostrovsky wrote:
> On 07/20/2015 10:09 AM, Dario Faggioli wrote:
>> On Fri, 2015-07-17 at 14:17 -0400, Boris Ostrovsky wrote:
>>> On 07/17/2015 03:27 AM, Dario Faggioli wrote:
>>>> In the meanwhile, what should we do? Document this? How? "don't use
>>>> vNUMA with PV guest in SMT enabled systems" seems a bit harsh... Is
>>>> there a workaround we can put in place/suggest?
>>> I haven't been able to reproduce this on my Intel box because I think I
>>> have different core enumeration.
>>>
>> Yes, most likely, that's highly topology dependant. :-(
>>
>>> Can you try adding
>>> cpuid=['0x1:ebx=xxxxxxxx00000001xxxxxxxxxxxxxxxx']
>>> to your config file?
>>>
>> Done (sorry for the delay, the testbox was busy doing other stuff).
>>
>> Still no joy (.101 is the IP address of the guest, domain id 3):
>>
>> root@Zhaman:~# ssh root@192.168.1.101 "yes > /dev/null 2>&1 &"
>> root@Zhaman:~# ssh root@192.168.1.101 "yes > /dev/null 2>&1 &"
>> root@Zhaman:~# ssh root@192.168.1.101 "yes > /dev/null 2>&1 &"
>> root@Zhaman:~# ssh root@192.168.1.101 "yes > /dev/null 2>&1 &"
>> root@Zhaman:~# xl vcpu-list 3
>> Name ID VCPU CPU State Time(s)
>> Affinity (Hard / Soft)
>> test 3 0 4 r-- 23.6 all / 0-7
>> test 3 1 9 r-- 19.8 all / 0-7
>> test 3 2 8 -b- 0.4 all / 8-15
>> test 3 3 4 -b- 0.2 all / 8-15
>>
>> *HOWEVER* it seems to have an effect. In fact, now, topology as it is
>> shown in /sys/... is different:
>>
>> root@test:~# cat
>> /sys/devices/system/cpu/cpu0/topology/thread_siblings_list
>> 0
>> (it was 0-1)
>>
>> This, OTOH, is still the same:
>> root@test:~# cat
>> /sys/devices/system/cpu/cpu0/topology/core_siblings_list
>> 0-3
>>
>> Also, I now see this:
>>
>> [ 0.150560] ------------[ cut here ]------------
>> [ 0.150560] WARNING: CPU: 2 PID: 0 at
>> ../arch/x86/kernel/smpboot.c:317 topology_sane.isra.2+0x74/0x88()
>> [ 0.150560] sched: CPU #2's llc-sibling CPU #0 is not on the same
>> node! [node: 1 != 0]. Ignoring dependency.
>> [ 0.150560] Modules linked in:
>> [ 0.150560] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 3.19.0+ #1
>> [ 0.150560] 0000000000000009 ffff88001ee2fdd0 ffffffff81657c7b
>> ffffffff810bbd2c
>> [ 0.150560] ffff88001ee2fe20 ffff88001ee2fe10 ffffffff81081510
>> ffff88001ee2fea0
>> [ 0.150560] ffffffff8103aa02 ffff88003ea0a001 0000000000000000
>> ffff88001f20a040
>> [ 0.150560] Call Trace:
>> [ 0.150560] [<ffffffff81657c7b>] dump_stack+0x4f/0x7b
>> [ 0.150560] [<ffffffff810bbd2c>] ? up+0x39/0x3e
>> [ 0.150560] [<ffffffff81081510>] warn_slowpath_common+0xa1/0xbb
>> [ 0.150560] [<ffffffff8103aa02>] ? topology_sane.isra.2+0x74/0x88
>> [ 0.150560] [<ffffffff81081570>] warn_slowpath_fmt+0x46/0x48
>> [ 0.150560] [<ffffffff8101eeb1>] ? __cpuid.constprop.0+0x15/0x19
>> [ 0.150560] [<ffffffff8103aa02>] topology_sane.isra.2+0x74/0x88
>> [ 0.150560] [<ffffffff8103acd0>] set_cpu_sibling_map+0x27a/0x444
>> [ 0.150560] [<ffffffff81056ac3>] ? numa_add_cpu+0x98/0x9f
>> [ 0.150560] [<ffffffff8100b8f2>] cpu_bringup+0x63/0xa8
>> [ 0.150560] [<ffffffff8100b945>] cpu_bringup_and_idle+0xe/0x1a
>> [ 0.150560] ---[ end trace 63d204896cce9f68 ]---
>>
>> Notice that it now says 'llc-sibling', while, before, it was saying
>> 'smt-sibling'.
>
> Exactly. You are now passing the first topology test which was to see
> that threads are on the same node. And since each processor has only
> one thread (as evidenced by thread_siblings_list) we are good.
>
> The second test checks that cores (i.e. things that share last level
> cache) are on the same node. And they are not.
>
>
>>
>>> On AMD, BTW, we fail a different test so some other bits probably need
>>> to be tweaked. You may fail it too (the LLC sanity check).
>>>
>> Yep, that's the one I guess. Should I try something more/else?
>
>
> I'll need to see how LLC IDs are calculated, probably also from some
> CPUID bits.
No, can't do this: LLC is calculated from CPUID leaf 4 (on Intel) which
use indexes in ECX register and xl syntax doesn't allow you to override
CPUIDs for such leaves.
-boris
> The question though will be --- what do we do with how cache sizes
> (and TLB sizes for that matter) are presented to the guests. Do we
> scale them down per thread?
>
> -boris
next prev parent reply other threads:[~2015-07-21 20:01 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-16 10:32 PV-vNUMA issue: topology is misinterpreted by the guest Dario Faggioli
2015-07-16 10:47 ` Jan Beulich
2015-07-16 10:56 ` Andrew Cooper
2015-07-16 15:25 ` Wei Liu
2015-07-16 15:45 ` Andrew Cooper
2015-07-16 15:50 ` Boris Ostrovsky
2015-07-16 16:29 ` Jan Beulich
2015-07-16 16:39 ` Andrew Cooper
2015-07-16 16:59 ` Boris Ostrovsky
2015-07-17 6:09 ` Jan Beulich
2015-07-17 7:27 ` Dario Faggioli
2015-07-17 7:42 ` Jan Beulich
2015-07-17 8:44 ` Wei Liu
2015-07-17 18:17 ` Boris Ostrovsky
2015-07-20 14:09 ` Dario Faggioli
2015-07-20 14:43 ` Boris Ostrovsky
2015-07-21 20:00 ` Boris Ostrovsky [this message]
2015-07-22 13:36 ` Dario Faggioli
2015-07-22 13:50 ` Juergen Gross
2015-07-22 13:58 ` Boris Ostrovsky
2015-07-22 14:09 ` Juergen Gross
2015-07-22 14:44 ` Boris Ostrovsky
2015-07-23 4:43 ` Juergen Gross
2015-07-23 7:28 ` Jan Beulich
2015-07-23 9:42 ` Andrew Cooper
2015-07-23 14:07 ` Dario Faggioli
2015-07-23 14:13 ` Juergen Gross
2015-07-24 10:28 ` Juergen Gross
2015-07-24 14:44 ` Dario Faggioli
2015-07-24 15:14 ` Juergen Gross
2015-07-24 15:24 ` Juergen Gross
2015-07-24 15:58 ` Dario Faggioli
2015-07-24 16:09 ` Konrad Rzeszutek Wilk
2015-07-24 16:14 ` Dario Faggioli
2015-07-24 16:18 ` Juergen Gross
2015-07-24 16:29 ` Konrad Rzeszutek Wilk
2015-07-24 16:39 ` Juergen Gross
2015-07-24 16:44 ` Boris Ostrovsky
2015-07-27 4:35 ` Juergen Gross
2015-07-27 10:43 ` George Dunlap
2015-07-27 10:54 ` Andrew Cooper
2015-07-27 11:13 ` Juergen Gross
2015-07-27 10:54 ` Juergen Gross
2015-07-27 11:11 ` George Dunlap
2015-07-27 12:01 ` Juergen Gross
2015-07-27 12:16 ` Tim Deegan
2015-07-27 13:23 ` Dario Faggioli
2015-07-27 14:02 ` Juergen Gross
2015-07-27 14:02 ` Dario Faggioli
2015-07-27 10:41 ` George Dunlap
2015-07-27 10:49 ` Andrew Cooper
2015-07-27 13:11 ` Dario Faggioli
2015-07-24 16:10 ` Juergen Gross
2015-07-24 16:40 ` Boris Ostrovsky
2015-07-24 16:48 ` Juergen Gross
2015-07-24 17:11 ` Boris Ostrovsky
2015-07-27 13:40 ` Dario Faggioli
2015-07-27 4:24 ` Juergen Gross
2015-07-27 14:09 ` Dario Faggioli
2015-07-27 14:34 ` Boris Ostrovsky
2015-07-27 14:43 ` Juergen Gross
2015-07-27 14:51 ` Boris Ostrovsky
2015-07-27 15:03 ` Juergen Gross
2015-07-27 14:47 ` Juergen Gross
2015-07-27 14:58 ` Dario Faggioli
2015-07-28 4:29 ` Juergen Gross
2015-07-28 15:11 ` Juergen Gross
2015-07-28 16:17 ` Dario Faggioli
2015-07-28 17:13 ` Dario Faggioli
2015-07-29 6:04 ` Juergen Gross
2015-07-29 7:09 ` Dario Faggioli
2015-07-29 7:44 ` Dario Faggioli
2015-07-24 16:05 ` Dario Faggioli
2015-07-28 10:05 ` Wei Liu
2015-07-28 15:17 ` Dario Faggioli
2015-07-24 20:27 ` Elena Ufimtseva
2015-07-22 14:50 ` Dario Faggioli
2015-07-22 15:32 ` Boris Ostrovsky
2015-07-22 15:49 ` Dario Faggioli
2015-07-22 18:10 ` Boris Ostrovsky
2015-07-23 7:25 ` Jan Beulich
2015-07-24 16:03 ` Boris Ostrovsky
2015-07-23 13:46 ` Dario Faggioli
2015-07-17 10:17 ` Andrew Cooper
2015-07-16 15:26 ` Wei Liu
2015-07-27 15:13 ` David Vrabel
2015-07-27 16:02 ` Dario Faggioli
2015-07-27 16:31 ` David Vrabel
2015-07-27 16:33 ` Andrew Cooper
2015-07-27 17:42 ` Dario Faggioli
2015-07-27 17:50 ` Konrad Rzeszutek Wilk
2015-07-27 23:19 ` Andrew Cooper
2015-07-28 3:52 ` Juergen Gross
2015-07-28 9:40 ` Andrew Cooper
2015-07-28 9:28 ` Dario Faggioli
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