linux-kernel - Re: [PATCH V4 01/27] kfifo: add kfifo_alloc

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Message-ID: <CADUfDZr0GqyWj=Zyq4WQ2T3wULrC_L4ZX_LB_CRbRj7TS=pmSg@mail.gmail.com>
Date: Sun, 30 Nov 2025 21:58:07 -0800
From: Caleb Sander Mateos <csander@...estorage.com>
To: Ming Lei <ming.lei@...hat.com>
Cc: Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org, 
	Uday Shankar <ushankar@...estorage.com>, Stefani Seibold <stefani@...bold.net>, 
	Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 01/27] kfifo: add kfifo_alloc_node() helper for NUMA awareness

On Sun, Nov 30, 2025 at 5:46 PM Ming Lei <ming.lei@...hat.com> wrote:
>
> On Sat, Nov 29, 2025 at 11:12:43AM -0800, Caleb Sander Mateos wrote:
> > On Thu, Nov 20, 2025 at 5:59 PM Ming Lei <ming.lei@...hat.com> wrote:
> > >
> > > Add __kfifo_alloc_node() by refactoring and reusing __kfifo_alloc(),
> > > and define kfifo_alloc_node() macro to support NUMA-aware memory
> > > allocation.
> > >
> > > The new __kfifo_alloc_node() function accepts a NUMA node parameter
> > > and uses kmalloc_array_node() instead of kmalloc_array() for
> > > node-specific allocation. The existing __kfifo_alloc() now calls
> > > __kfifo_alloc_node() with NUMA_NO_NODE to maintain backward
> > > compatibility.
> > >
> > > This enables users to allocate kfifo buffers on specific NUMA nodes,
> > > which is important for performance in NUMA systems where the kfifo
> > > will be primarily accessed by threads running on specific nodes.
> > >
> > > Cc: Stefani Seibold <stefani@...bold.net>
> > > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > > Cc: linux-kernel@...r.kernel.org
> > > Signed-off-by: Ming Lei <ming.lei@...hat.com>
> > > ---
> > >  include/linux/kfifo.h | 34 ++++++++++++++++++++++++++++++++--
> > >  lib/kfifo.c           |  8 ++++----
> > >  2 files changed, 36 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
> > > index fd743d4c4b4b..8b81ac74829c 100644
> > > --- a/include/linux/kfifo.h
> > > +++ b/include/linux/kfifo.h
> > > @@ -369,6 +369,30 @@ __kfifo_int_must_check_helper( \
> > >  }) \
> > >  )
> > >
> > > +/**
> > > + * kfifo_alloc_node - dynamically allocates a new fifo buffer on a NUMA node
> > > + * @fifo: pointer to the fifo
> > > + * @size: the number of elements in the fifo, this must be a power of 2
> > > + * @gfp_mask: get_free_pages mask, passed to kmalloc()
> > > + * @node: NUMA node to allocate memory on
> > > + *
> > > + * This macro dynamically allocates a new fifo buffer with NUMA node awareness.
> > > + *
> > > + * The number of elements will be rounded-up to a power of 2.
> > > + * The fifo will be release with kfifo_free().
> > > + * Return 0 if no error, otherwise an error code.
> > > + */
> > > +#define kfifo_alloc_node(fifo, size, gfp_mask, node) \
> > > +__kfifo_int_must_check_helper( \
> > > +({ \
> > > +       typeof((fifo) + 1) __tmp = (fifo); \
> > > +       struct __kfifo *__kfifo = &__tmp->kfifo; \
> > > +       __is_kfifo_ptr(__tmp) ? \
> > > +       __kfifo_alloc_node(__kfifo, size, sizeof(*__tmp->type), gfp_mask, node) : \
> > > +       -EINVAL; \
> > > +}) \
> > > +)
> >
> > Looks like we could avoid some code duplication by defining
> > kfifo_alloc(fifo, size, gfp_mask) as kfifo_alloc_node(fifo, size,
> > gfp_mask, NUMA_NO_NODE). Otherwise, this looks good to me.
>
> It is just a single-line inline, and shouldn't introduce any code
> duplication. Switching to kfifo_alloc_node() doesn't change result of
> `size vmlinux` actually.

Right, I know they expand to the same thing. I'm just saying we can
avoid repeating the nearly identical implementations by writing
kfifo_alloc() in terms of kfifo_alloc_node().

Best,
Caleb