linux-kernel - Re: [PATCH v2] neighbour: Don't let neigh_forced

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Message-ID: <20231206093917.04fd57b5@hermes.local>
Date:   Wed, 6 Dec 2023 09:39:17 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Judy Hsiao <judyhsiao@...omium.org>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        David Ahern <dsahern@...nel.org>,
        Simon Horman <horms@...nel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Brian Haley <haleyb.dev@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Joel Granados <joel.granados@...il.com>,
        Julian Anastasov <ja@....bg>,
        Leon Romanovsky <leon@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2] neighbour: Don't let neigh_forced_gc() disable
 preemption for long

On Wed,  6 Dec 2023 03:38:33 +0000
Judy Hsiao <judyhsiao@...omium.org> wrote:

> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index df81c1f0a570..552719c3bbc3 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -253,9 +253,11 @@ static int neigh_forced_gc(struct neigh_table *tbl)
>  {
>  	int max_clean = atomic_read(&tbl->gc_entries) -
>  			READ_ONCE(tbl->gc_thresh2);
> +	u64 tmax = ktime_get_ns() + NSEC_PER_MSEC;
>  	unsigned long tref = jiffies - 5 * HZ;
>  	struct neighbour *n, *tmp;
>  	int shrunk = 0;
> +	int loop = 0;
>  
>  	NEIGH_CACHE_STAT_INC(tbl, forced_gc_runs);
>  
> @@ -278,11 +280,16 @@ static int neigh_forced_gc(struct neigh_table *tbl)
>  				shrunk++;
>  			if (shrunk >= max_clean)
>  				break;
> +			if (++loop == 16) {

Overall looks good.
Minor comments:
	- loop count should probably be unsigned
        - the magic constant 16 should be a sysctl tuneable