From 4835f747d3ed181bf2c67930fe06b2c01a5d2323 Mon Sep 17 00:00:00 2001
From: Suren Baghdasaryan <surenb@google.com>
Date: Wed, 23 Oct 2024 10:07:59 -0700
Subject: alloc_tag: support for page allocation tag compression

Implement support for storing page allocation tag references directly in
the page flags instead of page extensions.  sysctl.vm.mem_profiling boot
parameter it extended to provide a way for a user to request this mode.
Enabling compression eliminates memory overhead caused by page_ext and
results in better performance for page allocations.  However this mode
will not work if the number of available page flag bits is insufficient to
address all kernel allocations.  Such condition can happen during boot or
when loading a module.  If this condition is detected, memory allocation
profiling gets disabled with an appropriate warning.  By default
compression mode is disabled.

Link: https://lkml.kernel.org/r/20241023170759.999909-7-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Daniel Gomez <da.gomez@samsung.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Minchan Kim <minchan@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Petr Pavlu <petr.pavlu@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xiongwei Song <xiongwei.song@windriver.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 Documentation/mm/allocation-profiling.rst | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

(limited to 'Documentation')

diff --git a/Documentation/mm/allocation-profiling.rst b/Documentation/mm/allocation-profiling.rst
index ffd6655b7be2..316311240e6a 100644
--- a/Documentation/mm/allocation-profiling.rst
+++ b/Documentation/mm/allocation-profiling.rst
@@ -18,12 +18,17 @@ kconfig options:
   missing annotation
 
 Boot parameter:
-  sysctl.vm.mem_profiling=0|1|never
+  sysctl.vm.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).
   When CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT=y, default value is "1".
   When CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT=n, default value is "never".
+  "compressed" optional parameter will try to store page tag references in a
+  compact format, avoiding page extensions. This results in improved performance
+  and memory consumption, however it might fail depending on system configuration.
+  If compression fails, a warning is issued and memory allocation profiling gets
+  disabled.
 
 sysctl:
   /proc/sys/vm/mem_profiling
-- 
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