[PATCH] Documentation: kdump: Clarify the default size of memory reserved by crashkernel low

[PATCH] Documentation: kdump: Clarify the default size of memory reserved by crashkernel low

[Pingfan Liu]

From: Pingfan Liu <piliu@redhat.com>

The default size reserved for crashkernel=,low is decided by the macro
DEFAULT_CRASH_KERNEL_LOW_SIZE, which is based on arch.

Signed-off-by: Pingfan Liu <piliu@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
To: kexec@lists.infradead.org
To: linux-doc@vger.kernel.org
---
 Documentation/admin-guide/kdump/kdump.rst | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
index 5762e7477a0c..a021ff155012 100644
--- a/Documentation/admin-guide/kdump/kdump.rst
+++ b/Documentation/admin-guide/kdump/kdump.rst
@@ -310,8 +310,9 @@ crashkernel syntax
    region above 4G, low memory under 4G is needed in this case. There are
    three ways to get low memory:
 
-      1) Kernel will allocate at least 256M memory below 4G automatically
-         if crashkernel=Y,low is not specified.
+      1) Kernel will allocate a chunk of default size memory, which is based on
+         architecture, below 4G automatically if crashkernel=Y,low is not
+         specified.
       2) Let user specify low memory size instead.
       3) Specified value 0 will disable low memory allocation::
 
-- 
2.31.1

Re: [PATCH] Documentation: kdump: Clarify the default size of memory reserved by crashkernel low

[Baoquan He]

On 12/18/23 at 11:40am, Pingfan Liu wrote:
> From: Pingfan Liu <piliu@redhat.com>
> 
> The default size reserved for crashkernel=,low is decided by the macro
> DEFAULT_CRASH_KERNEL_LOW_SIZE, which is based on arch.
> 
> Signed-off-by: Pingfan Liu <piliu@redhat.com>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Dave Young <dyoung@redhat.com>
> To: kexec@lists.infradead.org
> To: linux-doc@vger.kernel.org
> ---
>  Documentation/admin-guide/kdump/kdump.rst | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index 5762e7477a0c..a021ff155012 100644
> --- a/Documentation/admin-guide/kdump/kdump.rst
> +++ b/Documentation/admin-guide/kdump/kdump.rst
> @@ -310,8 +310,9 @@ crashkernel syntax
>     region above 4G, low memory under 4G is needed in this case. There are
>     three ways to get low memory:
>  
> -      1) Kernel will allocate at least 256M memory below 4G automatically
> -         if crashkernel=Y,low is not specified.
> +      1) Kernel will allocate a chunk of default size memory, which is based on
> +         architecture, below 4G automatically if crashkernel=Y,low is not
> +         specified.

Good catch, thx.

Acked-by: Baoquan He <bhe@redhat.com>

>        2) Let user specify low memory size instead.
>        3) Specified value 0 will disable low memory allocation::
>  
> -- 
> 2.31.1
> 

Re: [PATCH] Documentation: kdump: Clarify the default size of memory reserved by crashkernel low

[Baoquan He]

Hi Jonathan, Andrew,

On 12/18/23 at 11:40am, Pingfan Liu wrote:
> From: Pingfan Liu <piliu@redhat.com>
> 
> The default size reserved for crashkernel=,low is decided by the macro
> DEFAULT_CRASH_KERNEL_LOW_SIZE, which is based on arch.
> 
> Signed-off-by: Pingfan Liu <piliu@redhat.com>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Dave Young <dyoung@redhat.com>
> To: kexec@lists.infradead.org
> To: linux-doc@vger.kernel.org
> ---
>  Documentation/admin-guide/kdump/kdump.rst | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index 5762e7477a0c..a021ff155012 100644
> --- a/Documentation/admin-guide/kdump/kdump.rst
> +++ b/Documentation/admin-guide/kdump/kdump.rst
> @@ -310,8 +310,9 @@ crashkernel syntax
>     region above 4G, low memory under 4G is needed in this case. There are
>     three ways to get low memory:
>  
> -      1) Kernel will allocate at least 256M memory below 4G automatically
> -         if crashkernel=Y,low is not specified.
> +      1) Kernel will allocate a chunk of default size memory, which is based on
> +         architecture, below 4G automatically if crashkernel=Y,low is not
> +         specified.

This is a good catch in the obsolete section. Could any of you help
take this?

Thanks
Baoquan

>        2) Let user specify low memory size instead.
>        3) Specified value 0 will disable low memory allocation::
>  
> -- 
> 2.31.1
>