From: chenzhou <chenzhou10@huawei.com>
To: Dave Young <dyoung@redhat.com>
Cc: <catalin.marinas@arm.com>, <will@kernel.org>,
<james.morse@arm.com>, <tglx@linutronix.de>, <mingo@redhat.com>,
<bhe@redhat.com>, <corbet@lwn.net>, <John.P.donnelly@oracle.com>,
<prabhakar.pkin@gmail.com>, <bhsharma@redhat.com>,
<horms@verge.net.au>, <robh+dt@kernel.org>, <arnd@arndb.de>,
<nsaenzjulienne@suse.de>, <linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <kexec@lists.infradead.org>,
<linux-doc@vger.kernel.org>, <guohanjun@huawei.com>,
<xiexiuqi@huawei.com>, <huawei.libin@huawei.com>,
<wangkefeng.wang@huawei.com>
Subject: Re: [PATCH v11 5/5] kdump: update Documentation about crashkernel
Date: Mon, 10 Aug 2020 11:28:22 +0800 [thread overview]
Message-ID: <96d0da23-d484-7f66-1680-07b4b5984831@huawei.com> (raw)
In-Reply-To: <20200808100239.GB60590@dhcp-128-65.nay.redhat.com>
On 2020/8/8 18:02, Dave Young wrote:
> On 08/01/20 at 09:08pm, Chen Zhou wrote:
>> Now the behavior of crashkernel=X has been changed, which tries low
>> allocation in ZONE_DMA, and fall back to high allocation if it fails.
>>
>> If requized size X is too large and leads to very little free memory
>> in ZONE_DMA after low allocation, the system may not work well.
>> So add a threshold and go for high allocation directly if the required
>> size is too large. The threshold is set as the half of low memory.
>>
>> If crash_base is outside ZONE_DMA, try to allocate at least 256M in
>> ZONE_DMA automatically. "crashkernel=Y,low" can be used to allocate
>> specified size low memory. For non-RPi4 platforms, change ZONE_DMA
>> memtioned above to ZONE_DMA32.
>>
>> So update the Documentation.
>>
>> Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
>> ---
>> Documentation/admin-guide/kdump/kdump.rst | 21 ++++++++++++++++---
>> .../admin-guide/kernel-parameters.txt | 11 ++++++++--
>> 2 files changed, 27 insertions(+), 5 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
>> index 2da65fef2a1c..4b58f97351d5 100644
>> --- a/Documentation/admin-guide/kdump/kdump.rst
>> +++ b/Documentation/admin-guide/kdump/kdump.rst
>> @@ -299,7 +299,15 @@ Boot into System Kernel
>> "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
>> starting at physical address 0x01000000 (16MB) for the dump-capture kernel.
>>
>> - On x86 and x86_64, use "crashkernel=64M@16M".
>> + On x86 use "crashkernel=64M@16M".
>> +
>> + On x86_64, use "crashkernel=X" to select a region under 4G first, and
>> + fall back to reserve region above 4G.
>> + We can also use "crashkernel=X,high" to select a region above 4G, which
>> + also tries to allocate at least 256M below 4G automatically and
>> + "crashkernel=Y,low" can be used to allocate specified size low memory.
>> + Use "crashkernel=Y@X" if you really have to reserve memory from specified
>> + start address X.
>>
>> On ppc64, use "crashkernel=128M@32M".
>>
>> @@ -316,8 +324,15 @@ Boot into System Kernel
>> kernel will automatically locate the crash kernel image within the
>> first 512MB of RAM if X is not given.
>>
>> - On arm64, use "crashkernel=Y[@X]". Note that the start address of
>> - the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).
>> + On arm64, use "crashkernel=X" to try low allocation in ZONE_DMA, and
>> + fall back to high allocation if it fails. And go for high allocation
>> + directly if the required size is too large. If crash_base is outside
>> + ZONE_DMA, try to allocate at least 256M in ZONE_DMA automatically.
>> + "crashkernel=Y,low" can be used to allocate specified size low memory.
>> + For non-RPi4 platforms, change ZONE_DMA memtioned above to ZONE_DMA32.
>> + Use "crashkernel=Y@X" if you really have to reserve memory from
>> + specified start address X. Note that the start address of the kernel,
>> + X if explicitly specified, must be aligned to 2MiB (0x200000).
>>
>> Load the Dump-capture Kernel
>> ============================
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index fb95fad81c79..d1b6016850d6 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -722,6 +722,10 @@
>> [KNL, x86_64] select a region under 4G first, and
>> fall back to reserve region above 4G when '@offset'
>> hasn't been specified.
>> + [KNL, arm64] Try low allocation in ZONE_DMA, fall back
>> + to high allocation if it fails when '@offset' hasn't been
>> + specified. For non-RPi4 platforms, change ZONE_DMA to
>> + ZONE_DMA32.
>> See Documentation/admin-guide/kdump/kdump.rst for further details.
>>
>> crashkernel=range1:size1[,range2:size2,...][@offset]
>> @@ -746,13 +750,16 @@
>> requires at least 64M+32K low memory, also enough extra
>> low memory is needed to make sure DMA buffers for 32-bit
>> devices won't run out. Kernel would try to allocate at
>> - at least 256M below 4G automatically.
>> + least 256M below 4G automatically.
>> This one let user to specify own low range under 4G
>> for second kernel instead.
>> 0: to disable low allocation.
>> It will be ignored when crashkernel=X,high is not used
>> or memory reserved is below 4G.
>> -
>> + [KNL, arm64] range under 4G.
>> + This one let user to specify a low range in ZONE_DMA for
>> + crash dump kernel. For non-RPi4 platforms, change ZONE_DMA
>> + to ZONE_DMA32.
>> cryptomgr.notests
>> [KNL] Disable crypto self-tests
>>
>> --
>> 2.20.1
>>
> Hi Chen,
>
> Previously I remember we talked about to use similar logic as X86, but I
> remember you mentioned on some arm64 platform there could be no low
> memory at all. Is this not a problem now for the fallback? Just be
> curious, thanks for the update, for the common part looks good.
Hi Dave,
Did you mean this discuss: https://lkml.org/lkml/2019/12/27/122?
This is about the different implementation instead of no low memory in arm64.
On arm64 platform, if there is no low memory, system will boot fail.
Thanks,
Chen Zhou
>
> Acked-by: Dave Young <dyoung@redhat.com>
>
> Thanks
> Dave
>
>
> .
>
next prev parent reply other threads:[~2020-08-10 3:28 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-01 13:08 [PATCH v11 0/5] support reserving crashkernel above 4G on arm64 kdump Chen Zhou
2020-08-01 13:08 ` [PATCH v11 1/5] arm64: kdump: add macro CRASH_ALIGN and CRASH_ADDR_LOW_MAX Chen Zhou
2020-08-01 13:08 ` [PATCH v11 2/5] x86: kdump: move reserve_crashkernel_low() into crash_core.c Chen Zhou
2020-08-06 13:36 ` Ingo Molnar
2020-09-01 16:50 ` Catalin Marinas
2020-08-08 9:59 ` Dave Young
2020-08-01 13:08 ` [PATCH v11 3/5] arm64: kdump: reimplement crashkernel=X Chen Zhou
2020-09-02 17:09 ` Catalin Marinas
2020-09-03 11:26 ` chenzhou
2020-09-03 13:18 ` chenzhou
2020-09-04 3:04 ` Dave Young
2020-09-04 3:10 ` Dave Young
2020-09-04 4:02 ` chenzhou
2020-09-04 4:16 ` Dave Young
2020-09-04 6:39 ` chenzhou
2020-08-01 13:08 ` [PATCH v11 4/5] arm64: kdump: add memory for devices by DT property linux,usable-memory-range Chen Zhou
2020-08-01 13:08 ` [PATCH v11 5/5] kdump: update Documentation about crashkernel Chen Zhou
2020-08-08 10:02 ` Dave Young
2020-08-10 3:28 ` chenzhou [this message]
2020-08-10 5:59 ` Dave Young
2020-08-10 6:03 ` Dave Young
2020-08-18 7:07 ` chenzhou
2020-08-19 12:03 ` Dave Young
2020-08-28 1:59 ` chenzhou
2020-09-01 17:13 ` Catalin Marinas
2020-09-02 16:42 ` Catalin Marinas
2020-09-02 17:13 ` Catalin Marinas
2020-09-03 11:56 ` chenzhou
2020-08-06 11:37 ` [PATCH v11 0/5] support reserving crashkernel above 4G on arm64 kdump Dave Young
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