linux-kernel - Re: [PATCH v4 03/36] mm/slub: Mark slab_free_freelist_hook() __always

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Date: Mon, 26 Feb 2024 15:31:29 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Suren Baghdasaryan <surenb@...gle.com>,
 Pasha Tatashin <pasha.tatashin@...een.com>
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Subject: Re: [PATCH v4 03/36] mm/slub: Mark slab_free_freelist_hook()
 __always_inline

On 2/24/24 03:02, Suren Baghdasaryan wrote:
> On Wed, Feb 21, 2024 at 1:16 PM Pasha Tatashin
> <pasha.tatashin@...een.com> wrote:
>>
>> On Wed, Feb 21, 2024 at 2:41 PM Suren Baghdasaryan <surenb@...gle.com> wrote:
>> >
>> > From: Kent Overstreet <kent.overstreet@...ux.dev>
>> >
>> > It seems we need to be more forceful with the compiler on this one.
>> > This is done for performance reasons only.
>> >
>> > Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
>> > Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
>> > Reviewed-by: Kees Cook <keescook@...omium.org>
>> > ---
>> >  mm/slub.c | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/mm/slub.c b/mm/slub.c
>> > index 2ef88bbf56a3..d31b03a8d9d5 100644
>> > --- a/mm/slub.c
>> > +++ b/mm/slub.c
>> > @@ -2121,7 +2121,7 @@ bool slab_free_hook(struct kmem_cache *s, void *x, bool init)
>> >         return !kasan_slab_free(s, x, init);
>> >  }
>> >
>> > -static inline bool slab_free_freelist_hook(struct kmem_cache *s,
>> > +static __always_inline bool slab_free_freelist_hook(struct kmem_cache *s,
>>
>> __fastpath_inline seems to me more appropriate here. It prioritizes
>> memory vs performance.
> 
> Hmm. AFAIKT this function is used only in one place and we do not add
> any additional users, so I don't think changing to __fastpath_inline
> here would gain us anything.

It would have been more future-proof and self-documenting. But I don't insist.

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

>>
>> >                                            void **head, void **tail,
>> >                                            int *cnt)
>> >  {
>> > --
>> > 2.44.0.rc0.258.g7320e95886-goog
>> >