linux-kernel - Re: [PATCH] mm: simplify zone

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Message-ID: <CAGsJ_4wACEvWe-Fcx9fShkF8okEVb3srGDVCn0v0QjALq7nneg@mail.gmail.com>
Date: Fri, 11 Apr 2025 09:59:57 +1200
From: Barry Song <21cnbao@...il.com>
To: Mike Rapoport <rppt@...nel.org>
Cc: gaoxu <gaoxu2@...or.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	"surenb@...gle.com" <surenb@...gle.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, yipengxiang <yipengxiang@...or.com>
Subject: Re: [PATCH] mm: simplify zone_idx()

On Fri, Apr 11, 2025 at 2:42 AM Mike Rapoport <rppt@...nel.org> wrote:
>
> Hi,
>
> On Thu, Apr 10, 2025 at 12:03:00PM +0000, gaoxu wrote:
> > store zone_idx directly in struct zone to simplify and optimize zone_idx()
>
> Do you see an actual speed up somewhere?

+1. Curious if there's data indicating zone_idx is a hot path.

>
> > Signed-off-by: gao xu <gaoxu2@...or.com>
> > ---
> >  include/linux/mmzone.h | 3 ++-
> >  mm/mm_init.c           | 1 +
> >  2 files changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > index 4c95fcc9e..7b14f577d 100644
> > --- a/include/linux/mmzone.h
> > +++ b/include/linux/mmzone.h
> > @@ -941,6 +941,7 @@ struct zone {
> >  #endif
> >
> >       const char              *name;
> > +     enum zone_type  zone_idx;
> >
> >  #ifdef CONFIG_MEMORY_ISOLATION
> >       /*
> > @@ -1536,7 +1537,7 @@ static inline int local_memory_node(int node_id) { return node_id; };
> >  /*
> >   * zone_idx() returns 0 for the ZONE_DMA zone, 1 for the ZONE_NORMAL zone, etc.
> >   */
> > -#define zone_idx(zone)               ((zone) - (zone)->zone_pgdat->node_zones)
> > +#define zone_idx(zone)               ((zone)->zone_idx)
> >
> >  #ifdef CONFIG_ZONE_DEVICE
> >  static inline bool zone_is_zone_device(struct zone *zone)
> > diff --git a/mm/mm_init.c b/mm/mm_init.c
> > index 9659689b8..a7f7264f1 100644
> > --- a/mm/mm_init.c
> > +++ b/mm/mm_init.c
> > @@ -1425,6 +1425,7 @@ static void __meminit zone_init_internals(struct zone *zone, enum zone_type idx,
> >       atomic_long_set(&zone->managed_pages, remaining_pages);
> >       zone_set_nid(zone, nid);
> >       zone->name = zone_names[idx];
> > +     zone->zone_idx = idx;
> >       zone->zone_pgdat = NODE_DATA(nid);
> >       spin_lock_init(&zone->lock);
> >       zone_seqlock_init(zone);
> > --
> > 2.17.1
>
> --
> Sincerely yours,
> Mike.

Thanks
Barry