On Thu, Dec 26, 2024 at 01:16:38PM -0800, Suren Baghdasaryan wrote:
> 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.
I did it the other way because I was concerned about the overhead of
adding a huge number of static keys. But on further thought a static key
probably isn't any bigger than an alloc tag, no?
>
> Fixes: b951aaff5035 ("mm: enable page allocation tagging")
> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> include/linux/alloc_tag.h | 11 ++++++++---
> lib/alloc_tag.c | 2 ++
> 2 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
> index 0bbbe537c5f9..a946e0203e6d 100644
> --- a/include/linux/alloc_tag.h
> +++ b/include/linux/alloc_tag.h
> @@ -224,9 +224,14 @@ static inline void alloc_tag_sub(union codetag_ref *ref, size_t bytes) {}
>
> #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; \
> })
>
> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> index 7dcebf118a3e..4c373f444eb1 100644
> --- a/lib/alloc_tag.c
> +++ b/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 };
>
> base-commit: 431614f1580a03c1a653340c55ea76bd12a9403f
> --
> 2.47.1.613.gc27f4b7a9f-goog
>
