linux-kernel - Re: [PATCH v3 0/2] arm64: kdump: Function supplement and performance optimization

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Date:   Thu, 6 Oct 2022 09:55:35 -0500
From:   john.p.donnelly@...cle.com
To:     "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>,
        Baoquan He <bhe@...hat.com>
Cc:     Dave Young <dyoung@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Feng Zhou <zhoufeng.zf@...edance.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Chen Zhou <dingguo.cz@...group.com>,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        John Donnelly <john.p.donnelly@...cle.com>,
        "samasth.norway.ananda" <samasth.norway.ananda@...cle.com>
Subject: Re: [PATCH v3 0/2] arm64: kdump: Function supplement and performance
 optimization

On 8/1/22 9:47 PM, Leizhen (ThunderTown) wrote:
> 
> 
> On 2022/8/1 16:20, Baoquan He wrote:
>> Hi Catalin,
>>
>> On 07/11/22 at 05:03pm, Zhen Lei wrote:
>>> v2 --> v3:
>>> 1. Discard patch 3 in v2, a cleanup patch.
>>>
>>> v1 --> v2:
>>> 1. Update the commit message of Patch 1, explicitly indicates that "crashkernel=X,high"
>>>     is specified but "crashkernel=Y,low" is not specified.
>>> 2. Drop Patch 4-5. Currently, focus on function integrity, performance optimization
>>>     will be considered in later versions.
>>> 3. Patch 3 is not mandatory, it's just a cleanup now, although it is a must for patch 4-5.
>>>     But to avoid subsequent duplication of effort, I'm glad it was accepted.
>>>
>>>
>>> v1:
>>> After the basic functions of "support reserving crashkernel above 4G on arm64
>>> kdump"(see https://urldefense.com/v3/__https://lkml.org/lkml/2022/5/6/428__;!!ACWV5N9M2RV99hQ!ORBFa4UAmMss_79nuwu1kpW3D-mTela240vFo0FXOuV9QpGWy7Fp2H81ZjLPOuaufAQC_XBFEFGjAqs5njfGS6Rd4dZLhaez$ ) are implemented, we still have
>>> three features to be improved.
>>> 1. When crashkernel=X,high is specified but crashkernel=Y,low is not specified,
>>>     the default crash low memory size is provided.
>>> 2. For crashkernel=X without '@...set', if the low memory fails to be allocated,
>>>     fall back to reserve region from high memory(above DMA zones).
>>> 3. If crashkernel=X,high is used, page mapping is performed only for the crash
>>>     high memory, and block mapping is still used for other linear address spaces.
>>>     Compared to the previous version:
>>>     (1) For crashkernel=X[@offset], the memory above 4G is not changed to block
>>>         mapping, leave it to the next time.
>>>     (2) The implementation method is modified. Now the implementation is simpler
>>>         and clearer.
>>
>> Do you have plan to pick this series so that it can be taken into 5.20
>> rc-1~3?
> 
> Hi, Catalin:
>    Only function reserve_crashkernel() is modified in these two patches. The core
> process of the arm64 architecture is not affected. I remember you suggested that
> arm64 and x86 share the same kdump code, so these two subfeatures are needed.
> Maybe we can lay the foundation first for the people who build the road. Unifying
> the external interfaces of kdump on arm64 and x86 does not seem to hurt.
> 
> 
>>
>> We have back ported the basic crashkernel=high, low, support into our
>> distros and have taken wide testing on arm64 servers, need this patchset
>> to back port for more testing.
>>
>> Thanks
>> Baoquan
>>
>>>
>>> Zhen Lei (2):
>>>    arm64: kdump: Provide default size when crashkernel=Y,low is not
>>>      specified
>>>    arm64: kdump: Support crashkernel=X fall back to reserve region above
>>>      DMA zones
>>>
>>>   .../admin-guide/kernel-parameters.txt         | 10 ++-----
>>>   arch/arm64/mm/init.c                          | 28 +++++++++++++++++--
>>>   2 files changed, 28 insertions(+), 10 deletions(-)
>>>
>>> -- 
>>> 2.25.1
>>>
>>
>> .
>>
> 
Hi ,

What is the progress of this series ?

Without this patch set we are seeing  larger crashkernel=896M failures 
on Arm  with Linux-6.0.rc7.  This larger value is needed for
iSCSI booted systems with certain network adapters.


Thank you,
John.