linux-kernel - Re: kvm_intel: Could not allocate 42 bytes percpu data

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Message-ID: <51D3012A.4030306@hp.com>
Date:	Tue, 02 Jul 2013 09:34:50 -0700
From:	Chegu Vinod <chegu_vinod@...com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	prarit@...hat.com, LKML <linux-kernel@...r.kernel.org>,
	Gleb Natapov <gleb@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>, KVM <kvm@...r.kernel.org>,
	"Hull, Jim" <jim.hull@...com>
Subject: Re: kvm_intel: Could not allocate 42 bytes percpu data

On 7/1/2013 10:49 PM, Rusty Russell wrote:
> Chegu Vinod <chegu_vinod@...com> writes:
>> On 6/30/2013 11:22 PM, Rusty Russell wrote:
>>> Chegu Vinod <chegu_vinod@...com> writes:
>>>> Hello,
>>>>
>>>> Lots (~700+) of the following messages are showing up in the dmesg of a
>>>> 3.10-rc1 based kernel (Host OS is running on a large socket count box
>>>> with HT-on).
>>>>
>>>> [   82.270682] PERCPU: allocation failed, size=42 align=16, alloc from
>>>> reserved chunk failed
>>>> [   82.272633] kvm_intel: Could not allocate 42 bytes percpu data
>>> Woah, weird....
>>>
>>> Oh.  Shit.  Um, this is embarrassing.
>>>
>>> Thanks,
>>> Rusty.
>>
>> Thanks for your response!
>>
>>> ===
>>> module: do percpu allocation after uniqueness check.  No, really!
>>>
>>> v3.8-rc1-5-g1fb9341 was supposed to stop parallel kvm loads exhausting
>>> percpu memory on large machines:
>>>
>>>       Now we have a new state MODULE_STATE_UNFORMED, we can insert the
>>>       module into the list (and thus guarantee its uniqueness) before we
>>>       allocate the per-cpu region.
>>>
>>> In my defence, it didn't actually say the patch did this.  Just that
>>> we "can".
>>>
>>> This patch actually *does* it.
>>>
>>> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
>>> Tested-by: Noone it seems.
>> Your following "updated" fix seems to be working fine on the larger
>> socket count machine with HT-on.
> OK, did you definitely revert every other workaround?

Yes no other workarounds were there when your change was tested.

>
> If so, please give me a Tested-by: line...

FYI.... The actual verification of your change was done by my esteemed 
colleague :Jim Hull (cc'd) who had access to this larger socket count box.



Tested-by: Jim Hull <jim.hull@...com>




Thanks
Vinod


>
> Thanks,
> Rusty.
> .
>

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