Docs/mm/allocation-profiling: describe sysctrl limitations in debug mode

When CONFIG_MEM_ALLOC_PROFILING_DEBUG=y, /proc/sys/vm/mem_profiling is
read-only to avoid debug warnings in a scenario when an allocation is
made while profiling is disabled (allocation does not get an allocation
tag), then profiling gets enabled and allocation gets freed (warning due
to the allocation missing allocation tag).

Link: https://lkml.kernel.org/r/20260116184423.2708363-1-surenb@google.com
Fixes: ebdf9ad4ca98 ("memprofiling: documentation")
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
index 4d71211fdad8d061ccdef57477ce3dca5c78741d..245bf63949356c718597b91172f419e6f3770233 100644 (file)
--- a/Documentation/admin-guide/sysctl/vm.rst
+++ b/Documentation/admin-guide/sysctl/vm.rst
@@ -494,6 +494,10 @@ memory allocations.
 
 The default value depends on CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT.
 
+When CONFIG_MEM_ALLOC_PROFILING_DEBUG=y, this control is read-only to avoid
+warnings produced by allocations made while profiling is disabled and freed
+when it's enabled.
+
 
 memory_failure_early_kill
 =========================

diff --git a/Documentation/mm/allocation-profiling.rst b/Documentation/mm/allocation-profiling.rst
index 316311240e6aa3674f767dec6efd84b1a7679b00..5389d241176a8a4a8c7ec909f4f7cf6cf30c7ef9 100644 (file)
--- a/Documentation/mm/allocation-profiling.rst
+++ b/Documentation/mm/allocation-profiling.rst
@@ -33,6 +33,16 @@ Boot parameter:
 sysctl:
   /proc/sys/vm/mem_profiling
 
+  1: Enable memory profiling.
+
+  0: Disable memory profiling.
+
+  The default value depends on CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT.
+
+  When CONFIG_MEM_ALLOC_PROFILING_DEBUG=y, this control is read-only to avoid
+  warnings produced by allocations made while profiling is disabled and freed
+  when it's enabled.
+
 Runtime info:
   /proc/allocinfo