From: Chen Zhou <chenzhou10@huawei.com>
To: <catalin.marinas@arm.com>, <will@kernel.org>,
<james.morse@arm.com>, <tglx@linutronix.de>, <mingo@redhat.com>,
<dyoung@redhat.com>, <bhe@redhat.com>, <corbet@lwn.net>,
<John.P.donnelly@oracle.com>, <prabhakar.pkin@gmail.com>,
<bhsharma@redhat.com>
Cc: <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>, <chenzhou10@huawei.com>,
<guohanjun@huawei.com>, <xiexiuqi@huawei.com>,
<huawei.libin@huawei.com>, <wangkefeng.wang@huawei.com>
Subject: [PATCH v11 5/5] kdump: update Documentation about crashkernel
Date: Sat, 1 Aug 2020 21:08:56 +0800 [thread overview]
Message-ID: <20200801130856.86625-6-chenzhou10@huawei.com> (raw)
In-Reply-To: <20200801130856.86625-1-chenzhou10@huawei.com>
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
next prev parent reply other threads:[~2020-08-01 13:06 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 ` Chen Zhou [this message]
2020-08-08 10:02 ` [PATCH v11 5/5] kdump: update Documentation about crashkernel 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
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