linux-kernel - Re: [PATCH 4/8] mm/swap: Use local

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Date:   Wed, 20 May 2020 12:53:22 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Subject: Re: [PATCH 4/8] mm/swap: Use local_lock for protection

On Tue, May 19, 2020 at 10:19:08PM +0200, Sebastian Andrzej Siewior wrote:
> diff --git a/mm/swap.c b/mm/swap.c
> index bf9a79fed62d7..03c97d15fcd69 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -44,8 +44,14 @@
>  /* How many pages do we try to swap or page in/out together? */
>  int page_cluster;
>  
> -static DEFINE_PER_CPU(struct pagevec, lru_add_pvec);
> +
> +/* Protecting lru_rotate_pvecs */
> +static DEFINE_LOCAL_LOCK(rotate_lock);
>  static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
> +
> +/* Protecting the following struct pagevec */
> +DEFINE_LOCAL_LOCK(swapvec_lock);
> +static DEFINE_PER_CPU(struct pagevec, lru_add_pvec);
>  static DEFINE_PER_CPU(struct pagevec, lru_deactivate_file_pvecs);
>  static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
>  static DEFINE_PER_CPU(struct pagevec, lru_lazyfree_pvecs);

So personally I'd prefer to have this look like:

struct lru_vecs {
	struct local_lock lock;
	struct pagevec add;
	struct pagevec rotate;
	struct pagevec deact_file;
	struct pagevec deact;
	struct pagevec lazyfree;
#ifdef CONFIG_SMP
	struct pagevec active;
#endif
};

DEFINE_PER_CPU(struct lru_pvec, lru_pvec);

or something, but I realize that is a lot of churn (although highly
automated), so I'll leave that to the mm folks.