Linux-Doc Archive on lore.kernel.org
 help / color / Atom feed
From: chenzhou <chenzhou10@huawei.com>
To: Dave Young <dyoung@redhat.com>
Cc: Catalin Marinas <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 3/5] arm64: kdump: reimplement crashkernel=X
Date: Fri, 4 Sep 2020 12:02:05 +0800
Message-ID: <f4e0a246-0ca5-474b-8f39-c8299851d2b8@huawei.com> (raw)
In-Reply-To: <20200904031014.GA11869@dhcp-128-65.nay.redhat.com>



On 2020/9/4 11:10, Dave Young wrote:
> On 09/04/20 at 11:04am, Dave Young wrote:
>> On 09/03/20 at 07:26pm, chenzhou wrote:
>>> Hi Catalin,
>>>
>>>
>>> On 2020/9/3 1:09, Catalin Marinas wrote:
>>>> On Sat, Aug 01, 2020 at 09:08:54PM +0800, Chen Zhou wrote:
>>>>> There are following issues in arm64 kdump:
>>>>> 1. We use crashkernel=X to reserve crashkernel below 4G, which
>>>>> will fail when there is no enough low memory.
>>>>> 2. If reserving crashkernel above 4G, in this case, crash dump
>>>>> kernel will boot failure because there is no low memory available
>>>>> for allocation.
>>>>> 3. Since commit 1a8e1cef7603 ("arm64: use both ZONE_DMA and ZONE_DMA32"),
>>>>> if the memory reserved for crash dump kernel falled in ZONE_DMA32,
>>>>> the devices in crash dump kernel need to use ZONE_DMA will alloc
>>>>> fail.
>>>>>
>>>>> To solve these issues, change the behavior of crashkernel=X.
>>>>> crashkernel=X 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 normally.
>>>>> So add a threshold and go for high allocation directly if the required
>>>>> size is too large. The value of threshold is set as the half of
>>>>> the 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.
>>>> Except for the threshold to keep zone ZONE_DMA memory,
>>>> reserve_crashkernel() looks very close to the x86 version. Shall we try
>>>> to make this generic as well? In the first instance, you could avoid the
>>>> threshold check if it takes an explicit ",high" option.
>>> Ok, i will try to do this.
>>>
>>> I look into the function reserve_crashkernel() of x86 and found the start address is
>>> CRASH_ALIGN in function memblock_find_in_range(), which is different with arm64.
>>>
>>> I don't figure out why is CRASH_ALIGN in x86, is there any specific reason?
>> Hmm, took another look at the option CONFIG_PHYSICAL_ALIGN
>> config PHYSICAL_ALIGN
>>         hex "Alignment value to which kernel should be aligned"
>>         default "0x200000"
>>         range 0x2000 0x1000000 if X86_32
>>         range 0x200000 0x1000000 if X86_64
>>
>> According to above, I think the 16M should come from the largest value
>> But the default value is 2M,  with smaller value reservation can have
>> more chance to succeed.
>>
>> It seems we still need arch specific CRASH_ALIGN, but the initial
>> version you added the #ifdef for different arches, can you move the
>> macro to arch specific headers?
> And just keep the x86 align value as is, I can try to change the x86
> value later to CONFIG_PHYSICAL_ALIGN, in this way this series can be
> cleaner.
Ok. I have no question about the value of macro CRASH_ALIGN,
instead the lower bound of memblock_find_in_range().

For x86, in reserve_crashkernel(),restrict the lower bound of the range to CRASH_ALIGN,
    ...
    crash_base = memblock_find_in_range(CRASH_ALIGN,
                                                CRASH_ADDR_LOW_MAX,
                                                crash_size, CRASH_ALIGN);
    ...
   
in reserve_crashkernel_low(),with no this restriction.
    ...
    low_base = memblock_find_in_range(0, 1ULL << 32, low_size, CRASH_ALIGN);
    ...

How about all making memblock_find_in_range() search from the start of memory?
If it is ok, i will do like this in the generic version.

Thanks,
Chen Zhou
>
>> Thanks
>> Dave
>
> .
>



  reply index

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 [this message]
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=f4e0a246-0ca5-474b-8f39-c8299851d2b8@huawei.com \
    --to=chenzhou10@huawei.com \
    --cc=John.P.donnelly@oracle.com \
    --cc=arnd@arndb.de \
    --cc=bhe@redhat.com \
    --cc=bhsharma@redhat.com \
    --cc=catalin.marinas@arm.com \
    --cc=corbet@lwn.net \
    --cc=dyoung@redhat.com \
    --cc=guohanjun@huawei.com \
    --cc=horms@verge.net.au \
    --cc=huawei.libin@huawei.com \
    --cc=james.morse@arm.com \
    --cc=kexec@lists.infradead.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=nsaenzjulienne@suse.de \
    --cc=prabhakar.pkin@gmail.com \
    --cc=robh+dt@kernel.org \
    --cc=tglx@linutronix.de \
    --cc=wangkefeng.wang@huawei.com \
    --cc=will@kernel.org \
    --cc=xiexiuqi@huawei.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Doc Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-doc/0 linux-doc/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-doc linux-doc/ https://lore.kernel.org/linux-doc \
		linux-doc@vger.kernel.org
	public-inbox-index linux-doc

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-doc


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git