+ alloc_tag-avoid-current-alloc_tag-manipulations-when-profiling-is-disabled.patch added to mm-hotfixes-unstable branch

+ alloc_tag-avoid-current-alloc_tag-manipulations-when-profiling-is-disabled.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: alloc_tag: avoid current->alloc_tag manipulations when profiling is disabled
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     alloc_tag-avoid-current-alloc_tag-manipulations-when-profiling-is-disabled.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/alloc_tag-avoid-current-alloc_tag-manipulations-when-profiling-is-disabled.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Suren Baghdasaryan <surenb@google.com>
Subject: alloc_tag: avoid current->alloc_tag manipulations when profiling is disabled
Date: Thu, 26 Dec 2024 13:16:38 -0800

When memory allocation profiling is disabled there is no need to update
current->alloc_tag and these manipulations add unnecessary overhead.  Fix
the overhead by skipping these extra updates.

Link: https://lkml.kernel.org/r/20241226211639.1357704-1-surenb@google.com
Fixes: b951aaff5035 ("mm: enable page allocation tagging")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Cc: David Wang <00107082@163.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/alloc_tag.h |   11 ++++++++---
 lib/alloc_tag.c           |    2 ++
 2 files changed, 10 insertions(+), 3 deletions(-)

--- a/include/linux/alloc_tag.h~alloc_tag-avoid-current-alloc_tag-manipulations-when-profiling-is-disabled
+++ a/include/linux/alloc_tag.h
@@ -224,9 +224,14 @@ static inline void alloc_tag_sub(union c
 
 #define alloc_hooks_tag(_tag, _do_alloc)				\
 ({									\
-	struct alloc_tag * __maybe_unused _old = alloc_tag_save(_tag);	\
-	typeof(_do_alloc) _res = _do_alloc;				\
-	alloc_tag_restore(_tag, _old);					\
+	typeof(_do_alloc) _res;						\
+	if (mem_alloc_profiling_enabled()) {				\
+		struct alloc_tag * __maybe_unused _old;			\
+		_old = alloc_tag_save(_tag);				\
+		_res = _do_alloc;					\
+		alloc_tag_restore(_tag, _old);				\
+	} else								\
+		_res = _do_alloc;					\
 	_res;								\
 })
 
--- a/lib/alloc_tag.c~alloc_tag-avoid-current-alloc_tag-manipulations-when-profiling-is-disabled
+++ a/lib/alloc_tag.c
@@ -29,6 +29,8 @@ EXPORT_SYMBOL(_shared_alloc_tag);
 
 DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
 			mem_alloc_profiling_key);
+EXPORT_SYMBOL(mem_alloc_profiling_key);
+
 DEFINE_STATIC_KEY_FALSE(mem_profiling_compressed);
 
 struct alloc_tag_kernel_section kernel_tags = { NULL, 0 };
_

Patches currently in -mm which might be from surenb@google.com are

alloc_tag-avoid-current-alloc_tag-manipulations-when-profiling-is-disabled.patch
alloc_tag-skip-pgalloc_tag_swap-if-profiling-is-disabled.patch
seqlock-add-raw_seqcount_try_begin.patch
mm-convert-mm_lock_seq-to-a-proper-seqcount.patch
mm-introduce-mmap_lock_speculate_try_beginretry.patch
mm-introduce-vma_start_read_locked_nested-helpers.patch
mm-move-per-vma-lock-into-vm_area_struct.patch
mm-mark-vma-as-detached-until-its-added-into-vma-tree.patch
mm-modify-vma_iter_store_gfp-to-indicate-if-its-storing-a-new-vma.patch
mm-mark-vmas-detached-upon-exit.patch
mm-nommu-fix-the-last-places-where-vma-is-not-locked-before-being-attached.patch
types-move-struct-rcuwait-into-typesh.patch
mm-allow-vma_start_read_locked-vma_start_read_locked_nested-to-fail.patch
mm-move-mmap_init_lock-out-of-the-header-file.patch
mm-uninline-the-main-body-of-vma_start_write.patch
refcount-introduce-__refcount_addinc_not_zero_limited.patch
mm-replace-vm_lock-and-detached-flag-with-a-reference-count.patch
mm-debug-print-vm_refcnt-state-when-dumping-the-vma.patch
mm-debug-print-vm_refcnt-state-when-dumping-the-vma-fix.patch
mm-remove-extra-vma_numab_state_init-call.patch
mm-prepare-lock_vma_under_rcu-for-vma-reuse-possibility.patch
mm-make-vma-cache-slab_typesafe_by_rcu.patch
docs-mm-document-latest-changes-to-vm_lock.patch