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RE: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option

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  RE: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option "Izumi, Taku" <izumi.taku@jp.fujitsu.com> - 2015-12-17 02:40 +0100
    Re: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option Xishi Qiu <qiuxishi@huawei.com> - 2015-12-17 04:00 +0100
      Re: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> - 2015-12-17 04:00 +0100
        Re: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option Xishi Qiu <qiuxishi@huawei.com> - 2015-12-17 06:00 +0100
          Re: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> - 2015-12-17 06:10 +0100
            RE: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option "Luck, Tony" <tony.luck@intel.com> - 2015-12-17 19:50 +0100
              Re: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> - 2015-12-18 03:20 +0100
                RE: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option "Luck, Tony" <tony.luck@intel.com> - 2015-12-18 08:00 +0100

#1293546 — RE: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option

Dear Xishi,

 Sorry for late.

> -----Original Message-----
> From: Xishi Qiu [mailto:qiuxishi@huawei.com]
> Sent: Friday, December 11, 2015 6:44 PM
> To: Izumi, Taku/泉 拓
> Cc: Luck, Tony; linux-kernel@vger.kernel.org; linux-mm@kvack.org; akpm@linux-foundation.org; Kamezawa, Hiroyuki/亀澤 寛
> 之; mel@csn.ul.ie; Hansen, Dave; matt@codeblueprint.co.uk
> Subject: Re: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option
> 
> On 2015/12/11 13:53, Izumi, Taku wrote:
> 
> > Dear Xishi,
> >
> >> Hi Taku,
> >>
> >> Whether it is possible that we rewrite the fallback function in buddy system
> >> when zone_movable and mirrored_kernelcore are both enabled?
> >
> >   What does "when zone_movable and mirrored_kernelcore are both enabled?" mean ?
> >
> >   My patchset just provides a new way to create ZONE_MOVABLE.
> >
> 
> Hi Taku,
> 
> I mean when zone_movable is from kernelcore=mirror, not kernelcore=nn[KMG].

  I'm not quite sure what you are saying, but if you want to screen user memory
  so that one is allocated from mirrored zone and another is from non-mirrored zone,
  I think it is possible to reuse my patchset.

  Sincerely,
  Taku Izumi

> Thanks,
> Xishi Qiu
> 
> >   Sincerely,
> >   Taku Izumi
> >>
> >> It seems something like that we add a new zone but the name is zone_movable,
> >> not zone_mirror. And the prerequisite is that we won't enable these two
> >> features(movable memory and mirrored memory) at the same time. Thus we can
> >> reuse the code of movable zone.
> >>
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> >
> > .
> >
> 
> 

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#1293568

On 2015/12/17 9:38, Izumi, Taku wrote:

> Dear Xishi,
> 
>  Sorry for late.
> 
>> -----Original Message-----
>> From: Xishi Qiu [mailto:qiuxishi@huawei.com]
>> Sent: Friday, December 11, 2015 6:44 PM
>> To: Izumi, Taku/泉 拓
>> Cc: Luck, Tony; linux-kernel@vger.kernel.org; linux-mm@kvack.org; akpm@linux-foundation.org; Kamezawa, Hiroyuki/亀澤 寛
>> 之; mel@csn.ul.ie; Hansen, Dave; matt@codeblueprint.co.uk
>> Subject: Re: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option
>>
>> On 2015/12/11 13:53, Izumi, Taku wrote:
>>
>>> Dear Xishi,
>>>
>>>> Hi Taku,
>>>>
>>>> Whether it is possible that we rewrite the fallback function in buddy system
>>>> when zone_movable and mirrored_kernelcore are both enabled?
>>>
>>>   What does "when zone_movable and mirrored_kernelcore are both enabled?" mean ?
>>>
>>>   My patchset just provides a new way to create ZONE_MOVABLE.
>>>
>>
>> Hi Taku,
>>

Hi Taku,

We can NOT specify kernelcore= "nn[KMG]" and "mirror" at the same time.
So when we use "mirror", in fact, the movable zone is a new zone. I think it is
more appropriate with this name "mirrored zone", and also we can rewrite the
fallback function in buddy system in this case.

Thanks,
Xishi Qiu

>> I mean when zone_movable is from kernelcore=mirror, not kernelcore=nn[KMG].
> 
>   I'm not quite sure what you are saying, but if you want to screen user memory
>   so that one is allocated from mirrored zone and another is from non-mirrored zone,
>   I think it is possible to reuse my patchset.
> 
>   Sincerely,
>   Taku Izumi
> 
>> Thanks,
>> Xishi Qiu
>>
>>>   Sincerely,
>>>   Taku Izumi
>>>>
>>>> It seems something like that we add a new zone but the name is zone_movable,
>>>> not zone_mirror. And the prerequisite is that we won't enable these two
>>>> features(movable memory and mirrored memory) at the same time. Thus we can
>>>> reuse the code of movable zone.
>>>>
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>> Please read the FAQ at  http://www.tux.org/lkml/
>>>
>>> .
>>>
>>
>>
> 
> 
> .
> 



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#1293570

On 2015/12/17 11:47, Xishi Qiu wrote:
> On 2015/12/17 9:38, Izumi, Taku wrote:
> 
>> Dear Xishi,
>>
>>   Sorry for late.
>>
>>> -----Original Message-----
>>> From: Xishi Qiu [mailto:qiuxishi@huawei.com]
>>> Sent: Friday, December 11, 2015 6:44 PM
>>> To: Izumi, Taku/泉 拓
>>> Cc: Luck, Tony; linux-kernel@vger.kernel.org; linux-mm@kvack.org; akpm@linux-foundation.org; Kamezawa, Hiroyuki/亀澤 寛
>>> 之; mel@csn.ul.ie; Hansen, Dave; matt@codeblueprint.co.uk
>>> Subject: Re: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option
>>>
>>> On 2015/12/11 13:53, Izumi, Taku wrote:
>>>
>>>> Dear Xishi,
>>>>
>>>>> Hi Taku,
>>>>>
>>>>> Whether it is possible that we rewrite the fallback function in buddy system
>>>>> when zone_movable and mirrored_kernelcore are both enabled?
>>>>
>>>>    What does "when zone_movable and mirrored_kernelcore are both enabled?" mean ?
>>>>
>>>>    My patchset just provides a new way to create ZONE_MOVABLE.
>>>>
>>>
>>> Hi Taku,
>>>
> 
> Hi Taku,
> 
> We can NOT specify kernelcore= "nn[KMG]" and "mirror" at the same time.
> So when we use "mirror", in fact, the movable zone is a new zone. I think it is
> more appropriate with this name "mirrored zone", and also we can rewrite the
> fallback function in buddy system in this case.

kernelcore ="mirrored zone" ?

BTW, let me confirm.

  ZONE_NORMAL = mirrored
  ZONE_MOVABLE = not mirrored.

so, the new zone is "not-mirrored" zone.

Now, fallback function is

   movable -> normal -> DMA.

As Tony requested, we may need a knob to stop a fallback in "movable->normal", later.

Thanks,
-Kame






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#1293609

On 2015/12/17 10:53, Kamezawa Hiroyuki wrote:

> On 2015/12/17 11:47, Xishi Qiu wrote:
>> On 2015/12/17 9:38, Izumi, Taku wrote:
>>
>>> Dear Xishi,
>>>
>>>   Sorry for late.
>>>
>>>> -----Original Message-----
>>>> From: Xishi Qiu [mailto:qiuxishi@huawei.com]
>>>> Sent: Friday, December 11, 2015 6:44 PM
>>>> To: Izumi, Taku/泉 拓
>>>> Cc: Luck, Tony; linux-kernel@vger.kernel.org; linux-mm@kvack.org; akpm@linux-foundation.org; Kamezawa, Hiroyuki/亀澤 寛
>>>> 之; mel@csn.ul.ie; Hansen, Dave; matt@codeblueprint.co.uk
>>>> Subject: Re: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option
>>>>
>>>> On 2015/12/11 13:53, Izumi, Taku wrote:
>>>>
>>>>> Dear Xishi,
>>>>>
>>>>>> Hi Taku,
>>>>>>
>>>>>> Whether it is possible that we rewrite the fallback function in buddy system
>>>>>> when zone_movable and mirrored_kernelcore are both enabled?
>>>>>
>>>>>    What does "when zone_movable and mirrored_kernelcore are both enabled?" mean ?
>>>>>
>>>>>    My patchset just provides a new way to create ZONE_MOVABLE.
>>>>>
>>>>
>>>> Hi Taku,
>>>>
>>
>> Hi Taku,
>>
>> We can NOT specify kernelcore= "nn[KMG]" and "mirror" at the same time.
>> So when we use "mirror", in fact, the movable zone is a new zone. I think it is
>> more appropriate with this name "mirrored zone", and also we can rewrite the
>> fallback function in buddy system in this case.
> 
> kernelcore ="mirrored zone" ?

No, it's zone_names[MAX_NR_ZONES]
How about "Movable", -> "Non-mirrored"?

> 
> BTW, let me confirm.
> 
>   ZONE_NORMAL = mirrored
>   ZONE_MOVABLE = not mirrored.
> 

Yes, 

> so, the new zone is "not-mirrored" zone.
> 
> Now, fallback function is
> 
>    movable -> normal -> DMA.
> 
> As Tony requested, we may need a knob to stop a fallback in "movable->normal", later.
> 

If the mirrored memory is small and the other is large,
I think we can both enable "non-mirrored -> normal" and "normal -> non-mirrored".

Thanks,
Xishi Qiu

> Thanks,
> -Kame
> 
> 
> 
> 
> 
> 
> 
> .
> 



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#1293611

On 2015/12/17 13:48, Xishi Qiu wrote:
> On 2015/12/17 10:53, Kamezawa Hiroyuki wrote:
> 
>> On 2015/12/17 11:47, Xishi Qiu wrote:
>>> On 2015/12/17 9:38, Izumi, Taku wrote:
>>>
>>>> Dear Xishi,
>>>>
>>>>    Sorry for late.
>>>>
>>>>> -----Original Message-----
>>>>> From: Xishi Qiu [mailto:qiuxishi@huawei.com]
>>>>> Sent: Friday, December 11, 2015 6:44 PM
>>>>> To: Izumi, Taku/泉 拓
>>>>> Cc: Luck, Tony; linux-kernel@vger.kernel.org; linux-mm@kvack.org; akpm@linux-foundation.org; Kamezawa, Hiroyuki/亀澤 寛
>>>>> 之; mel@csn.ul.ie; Hansen, Dave; matt@codeblueprint.co.uk
>>>>> Subject: Re: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option
>>>>>
>>>>> On 2015/12/11 13:53, Izumi, Taku wrote:
>>>>>
>>>>>> Dear Xishi,
>>>>>>
>>>>>>> Hi Taku,
>>>>>>>
>>>>>>> Whether it is possible that we rewrite the fallback function in buddy system
>>>>>>> when zone_movable and mirrored_kernelcore are both enabled?
>>>>>>
>>>>>>     What does "when zone_movable and mirrored_kernelcore are both enabled?" mean ?
>>>>>>
>>>>>>     My patchset just provides a new way to create ZONE_MOVABLE.
>>>>>>
>>>>>
>>>>> Hi Taku,
>>>>>
>>>
>>> Hi Taku,
>>>
>>> We can NOT specify kernelcore= "nn[KMG]" and "mirror" at the same time.
>>> So when we use "mirror", in fact, the movable zone is a new zone. I think it is
>>> more appropriate with this name "mirrored zone", and also we can rewrite the
>>> fallback function in buddy system in this case.
>>
>> kernelcore ="mirrored zone" ?
> 
> No, it's zone_names[MAX_NR_ZONES]
> How about "Movable", -> "Non-mirrored"?
> 
That will break many user apps. I think we don't have enough reason. 

>>
>> BTW, let me confirm.
>>
>>    ZONE_NORMAL = mirrored
>>    ZONE_MOVABLE = not mirrored.
>>
> 
> Yes,
> 
>> so, the new zone is "not-mirrored" zone.
>>
>> Now, fallback function is
>>
>>     movable -> normal -> DMA.
>>
>> As Tony requested, we may need a knob to stop a fallback in "movable->normal", later.
>>
> 
> If the mirrored memory is small and the other is large,
> I think we can both enable "non-mirrored -> normal" and "normal -> non-mirrored".

Size of mirrored memory can be configured by software(EFI var).
So, having both is just overkill and normal->non-mirroed fallback is meaningless considering
what the feature want to guarantee.

Thanks,
-Kame




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#1294133

>>> As Tony requested, we may need a knob to stop a fallback in "movable->normal", later.
>>>
>> 
>> If the mirrored memory is small and the other is large,
>> I think we can both enable "non-mirrored -> normal" and "normal -> non-mirrored".
>
> Size of mirrored memory can be configured by software(EFI var).
> So, having both is just overkill and normal->non-mirroed fallback is meaningless considering
> what the feature want to guarantee.

In the original removable usage we wanted to guarantee that Linux did not allocate any
kernel objects in removable memory - because that would prevent later removal of that
memory.

Mirror case is the same - we don't want to allocate kernel structures in non-mirrored memory
because an uncorrectable error in one of them would crash the system.

But I think some users might like some flexibility here.  If the system doesn't have enough
memory for the kernel (non-movable or mirrored), then it seems odd to end up crashing
the system at the point of memory exhaustion (a likely result ... the kernel can try to reclaim
some pages from SLAB, but that might only return a few pages, if the shortage continues
the system will perform poorly and eventually fail).

The whole point of removable memory or mirrored memory is to provide better availability.

I'd vote for a mode where running out of memory for kernel results in a

   warn_on_once("Ran out of mirrored/non-removable memory for kernel - now allocating from all zones\n")

because I think most people would like the system to stay up rather than worry about some future problem that may never happen.

-Tony



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#1294397

On 2015/12/18 3:43, Luck, Tony wrote:
>>>> As Tony requested, we may need a knob to stop a fallback in "movable->normal", later.
>>>>
>>>
>>> If the mirrored memory is small and the other is large,
>>> I think we can both enable "non-mirrored -> normal" and "normal -> non-mirrored".
>>
>> Size of mirrored memory can be configured by software(EFI var).
>> So, having both is just overkill and normal->non-mirroed fallback is meaningless considering
>> what the feature want to guarantee.
>
> In the original removable usage we wanted to guarantee that Linux did not allocate any
> kernel objects in removable memory - because that would prevent later removal of that
> memory.
>
> Mirror case is the same - we don't want to allocate kernel structures in non-mirrored memory
> because an uncorrectable error in one of them would crash the system.
>
> But I think some users might like some flexibility here.  If the system doesn't have enough
> memory for the kernel (non-movable or mirrored), then it seems odd to end up crashing
> the system at the point of memory exhaustion (a likely result ... the kernel can try to reclaim
> some pages from SLAB, but that might only return a few pages, if the shortage continues
> the system will perform poorly and eventually fail).
>
> The whole point of removable memory or mirrored memory is to provide better availability.
>
> I'd vote for a mode where running out of memory for kernel results in a
>
>     warn_on_once("Ran out of mirrored/non-removable memory for kernel - now allocating from all zones\n")
>
> because I think most people would like the system to stay up rather than worry about some future problem that may never happen.

Hmm...like this ?
       sysctl.vm.fallback_mirror_memory = 0  // never fallback  # default.
       sysctl.vm.fallback_mirror_memory = 1  // the user memory may be allocated from mirrored zone.
       sysctl.vm.fallback_mirror_memory = 2  // usually kernel allocates memory from mirrored zone before OOM.
       sysctl.vm.fallback_mirror_memory = 3  // 1+2

However I believe my customer's choice is always 0, above implementation can be done in a clean way.
(adding a flag to zones (mirrored or not) and controlling fallback zonelist walk.)

BTW, we need this Taku's patch to make a progress. I think other devs should be done in another
development cycle. What does he need to get your Acks ?

Thanks,
-Kame




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#1294460

>Hmm...like this ?
>       sysctl.vm.fallback_mirror_memory = 0  // never fallback  # default.
>       sysctl.vm.fallback_mirror_memory = 1  // the user memory may be allocated from mirrored zone.
>       sysctl.vm.fallback_mirror_memory = 2  // usually kernel allocates memory from mirrored zone before OOM.
>       sysctl.vm.fallback_mirror_memory = 3  // 1+2

Should option 2 say: // allow kernel to allocate from non-mirror zone to avoid OOM

> However I believe my customer's choice is always 0, above implementation can be done in a clean way.
> (adding a flag to zones (mirrored or not) and controlling fallback zonelist walk.)

Modes allow us to make all of the people happy (I hope).

> BTW, we need this Taku's patch to make a progress. I think other devs should be done in another
> development cycle. What does he need to get your Acks ?

The concept is great.   It's even "Tested-by: Tony Luck <tony.luck@intel.com>".
I need to read the code more carefully before Acked-by.

-Tony
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