The patch titled
Subject: lib: introduce early boot parameter to avoid page_ext memory overhead
has been added to the -mm mm-unstable branch. Its filename is
lib-introduce-early-boot-parameter-to-avoid-page_ext-memory-overhead.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-introduce-early-boot-parameter-to-avoid-page_ext-memory-overhead.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Subject: lib: introduce early boot parameter to avoid page_ext memory overhead
Date: Thu, 21 Mar 2024 09:36:37 -0700
The highest memory overhead from memory allocation profiling comes from
page_ext objects. This overhead exists even if the feature is disabled
but compiled-in. To avoid it, introduce an early boot parameter that
prevents page_ext object creation. The new boot parameter is a tri-state
with possible values of 0|1|never. When it is set to "never" the memory
allocation profiling support is disabled, and overhead is minimized
(currently no page_ext objects are allocated, in the future more overhead
might be eliminated). As a result we also lose ability to enable memory
allocation profiling at runtime (because there is no space to store
alloctag references). Runtime sysctrl becomes read-only if the early boot
parameter was set to "never". Note that the default value of this boot
parameter depends on the CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT
configuration. When CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT=n the
boot parameter is set to "never", therefore eliminating any overhead.
CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT=y results in boot parameter
being set to 1 (enabled). This allows distributions to avoid any overhead
by setting CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT=n config and with
no changes to the kernel command line.
We reuse sysctl.vm.mem_profiling boot parameter name in order to avoid
introducing yet another control. This change turns it into a tri-state
early boot parameter.
Link: https://lkml.kernel.org/r/20240321163705.3067592-16-surenb@xxxxxxxxxx
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Alex Gaynor <alex.gaynor@xxxxxxxxx>
Cc: Alice Ryhl <aliceryhl@xxxxxxxxxx>
Cc: Andreas Hindborg <a.hindborg@xxxxxxxxxxx>
Cc: Benno Lossin <benno.lossin@xxxxxxxxx>
Cc: "Björn Roy Baron" <bjorn3_gh@xxxxxxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Dennis Zhou <dennis@xxxxxxxxxx>
Cc: Gary Guo <gary@xxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx>
Cc: Miguel Ojeda <ojeda@xxxxxxxxxx>
Cc: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Wedson Almeida Filho <wedsonaf@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/alloc_tag.c | 41 ++++++++++++++++++++++++++++++++++++++++-
1 file changed, 40 insertions(+), 1 deletion(-)
--- a/lib/alloc_tag.c~lib-introduce-early-boot-parameter-to-avoid-page_ext-memory-overhead
+++ a/lib/alloc_tag.c
@@ -116,9 +116,46 @@ static bool alloc_tag_module_unload(stru
return module_unused;
}
+#ifdef CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT
+static bool mem_profiling_support __meminitdata = true;
+#else
+static bool mem_profiling_support __meminitdata;
+#endif
+
+static int __init setup_early_mem_profiling(char *str)
+{
+ bool enable;
+
+ if (!str || !str[0])
+ return -EINVAL;
+
+ if (!strncmp(str, "never", 5)) {
+ enable = false;
+ mem_profiling_support = false;
+ } else {
+ int res;
+
+ res = kstrtobool(str, &enable);
+ if (res)
+ return res;
+
+ mem_profiling_support = true;
+ }
+
+ if (enable != static_key_enabled(&mem_alloc_profiling_key)) {
+ if (enable)
+ static_branch_enable(&mem_alloc_profiling_key);
+ else
+ static_branch_disable(&mem_alloc_profiling_key);
+ }
+
+ return 0;
+}
+early_param("sysctl.vm.mem_profiling", setup_early_mem_profiling);
+
static __init bool need_page_alloc_tagging(void)
{
- return true;
+ return mem_profiling_support;
}
static __init void init_page_alloc_tagging(void)
@@ -158,6 +195,8 @@ static int __init alloc_tag_init(void)
if (IS_ERR_OR_NULL(alloc_tag_cttype))
return PTR_ERR(alloc_tag_cttype);
+ if (!mem_profiling_support)
+ memory_allocation_profiling_sysctls[0].mode = 0444;
register_sysctl_init("vm", memory_allocation_profiling_sysctls);
procfs_init();
_
Patches currently in -mm which might be from surenb@xxxxxxxxxx are
mm-introduce-slabobj_ext-to-support-slab-object-extensions.patch
mm-introduce-__gfp_no_obj_ext-flag-to-selectively-prevent-slabobj_ext-creation.patch
mm-slab-introduce-slab_no_obj_ext-to-avoid-obj_ext-creation.patch
slab-objext-introduce-objext_flags-as-extension-to-page_memcg_data_flags.patch
lib-code-tagging-framework.patch
lib-code-tagging-module-support.patch
lib-prevent-module-unloading-if-memory-is-not-freed.patch
lib-add-allocation-tagging-support-for-memory-allocation-profiling.patch
lib-introduce-support-for-page-allocation-tagging.patch
lib-introduce-early-boot-parameter-to-avoid-page_ext-memory-overhead.patch
mm-percpu-increase-percpu_module_reserve-to-accommodate-allocation-tags.patch
change-alloc_pages-name-in-dma_map_ops-to-avoid-name-conflicts.patch
mm-enable-page-allocation-tagging.patch
mm-create-new-codetag-references-during-page-splitting.patch
mm-fix-non-compound-multi-order-memory-accounting-in-__free_pages.patch
mm-page_ext-enable-early_page_ext-when-config_mem_alloc_profiling_debug=y.patch
lib-add-codetag-reference-into-slabobj_ext.patch
mm-slab-add-allocation-accounting-into-slab-allocation-and-free-paths.patch
mm-slab-enable-slab-allocation-tagging-for-kmalloc-and-friends.patch
mm-percpu-enable-per-cpu-allocation-tagging.patch
lib-add-memory-allocations-report-in-show_mem.patch
codetag-debug-skip-objext-checking-when-its-for-objext-itself.patch
codetag-debug-mark-codetags-for-reserved-pages-as-empty.patch
codetag-debug-introduce-objexts_alloc_fail-to-mark-failed-slab_ext-allocations.patch
