Linux-Doc Archive on lore.kernel.org
 help / color / Atom feed
From: Dave Young <dyoung@redhat.com>
To: chenzhou <chenzhou10@huawei.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 12:16:33 +0800
Message-ID: <20200904041633.GB11869@dhcp-128-65.nay.redhat.com> (raw)
In-Reply-To: <f4e0a246-0ca5-474b-8f39-c8299851d2b8@huawei.com>

On 09/04/20 at 12:02pm, chenzhou wrote:
> 
> 
> 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.

I feel starting with CRASH_ALIGN sounds better, can you just search from
CRASH_ALIGN in generic version?

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
2020-09-04  4:16             ` Dave Young [this message]
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=20200904041633.GB11869@dhcp-128-65.nay.redhat.com \
    --to=dyoung@redhat.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=chenzhou10@huawei.com \
    --cc=corbet@lwn.net \
    --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