[PATCH] alloc_tag: remove sysctl prefix from mem_profiling boot parameter

[PATCH] alloc_tag: remove sysctl prefix from mem_profiling boot parameter

[ranxiaokai627]

From: Ran Xiaokai <ran.xiaokai@zte.com.cn>

Boot parameters prefixed with "sysctl." are processed separately
during the final stage of system initialization via kernel_init()->
do_sysctl_args(). Since mem_profiling support should be parsed
in early boot stage, it is unsuitable for centralized handling
in do_sysctl_args().
Also, when CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled,
the sysctl.vm.mem_profiling entry is not writable and will cause
a warning. To prevent duplicate processing of sysctl.vm.mem_profiling,
rename the boot parameter to "mem_profiling".

Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
---
 Documentation/mm/allocation-profiling.rst | 2 +-
 lib/alloc_tag.c                           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/mm/allocation-profiling.rst b/Documentation/mm/allocation-profiling.rst
index 316311240e6a..fe341d6da7b9 100644
--- a/Documentation/mm/allocation-profiling.rst
+++ b/Documentation/mm/allocation-profiling.rst
@@ -18,7 +18,7 @@ kconfig options:
   missing annotation
 
 Boot parameter:
-  sysctl.vm.mem_profiling={0|1|never}[,compressed]
+  mem_profiling={0|1|never}[,compressed]
 
   When set to "never", memory allocation profiling overhead is minimized and it
   cannot be enabled at runtime (sysctl becomes read-only).
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 846a5b5b44a4..81b248196629 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -747,7 +747,7 @@ static int __init setup_early_mem_profiling(char *str)
 
 	return 0;
 }
-early_param("sysctl.vm.mem_profiling", setup_early_mem_profiling);
+early_param("mem_profiling", setup_early_mem_profiling);
 
 static __init bool need_page_alloc_tagging(void)
 {
-- 
2.25.1

Re: [PATCH] alloc_tag: remove sysctl prefix from mem_profiling boot parameter

[Andrew Morton]

On Fri,  9 Jan 2026 06:24:19 +0000 ranxiaokai627@163.com wrote:

> From: Ran Xiaokai <ran.xiaokai@zte.com.cn>
> 
> Boot parameters prefixed with "sysctl." are processed separately
> during the final stage of system initialization via kernel_init()->
> do_sysctl_args(). Since mem_profiling support should be parsed
> in early boot stage, it is unsuitable for centralized handling
> in do_sysctl_args().
> Also, when CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled,
> the sysctl.vm.mem_profiling entry is not writable and will cause
> a warning. To prevent duplicate processing of sysctl.vm.mem_profiling,
> rename the boot parameter to "mem_profiling".

Isn't this a backwardly-incompatible change?  What happens to existing
steups which are using sysctl.vm.mem_profiling=?

Re: [PATCH] alloc_tag: remove sysctl prefix from mem_profiling boot parameter

[Kent Overstreet]

On Fri, Jan 09, 2026 at 06:24:19AM +0000, ranxiaokai627@163.com wrote:
> From: Ran Xiaokai <ran.xiaokai@zte.com.cn>
> 
> Boot parameters prefixed with "sysctl." are processed separately
> during the final stage of system initialization via kernel_init()->
> do_sysctl_args(). Since mem_profiling support should be parsed
> in early boot stage, it is unsuitable for centralized handling
> in do_sysctl_args().
> Also, when CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled,
> the sysctl.vm.mem_profiling entry is not writable and will cause
> a warning. To prevent duplicate processing of sysctl.vm.mem_profiling,
> rename the boot parameter to "mem_profiling".
> 
> Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>

How was this observed/detected?

My reading of early_param() would seem to indicate that
setup_early_mem_profiling() is getting called at the appropriate time -
and then additionally a second time by do_sysctl_args(), which then
becomes a noop.

So the only bug would seem to be that the sysctl is not writeable in
debug mode? There's an easier fix for that one...