linux-kernel - Re: [PATCH v2 4/6] debugobjects: Don't start fill if there are remaining nodes locally

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Message-ID: <8bc3ebed-f092-6842-bd8b-a8b4b1b30cf1@huawei.com>
Date: Tue, 10 Sep 2024 23:29:13 +0800
From: "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To: Thomas Gleixner <tglx@...utronix.de>, Andrew Morton
	<akpm@...ux-foundation.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/6] debugobjects: Don't start fill if there are
 remaining nodes locally



On 2024/9/9 21:51, Leizhen (ThunderTown) wrote:
> +static void fill_pool(void)
> +{
> +	gfp_t gfp = __GFP_HIGH | __GFP_NOWARN;
> +	static atomic_t cpus_allocating;
>  
>  	if (unlikely(!obj_cache))
>  		return;
>  
> +	/*
> +	 * Avoid allocation and lock contention when
> +	 *
> +	 *   - the CPU local pool has at least 2 objects left
> +	 *   - another CPU is already in the allocation path
> +	 *   - the global pool has not reached the critical level yet
> +	 */
> +	if (this_cpu_read(percpu_obj_pool.obj_free) > 1 && atomic_read(&cpus_allocating) &&

I rethink that 'cpus_allocating' and 'percpu_obj_pool.obj_free > 1' should be
contradictory. We can only choose one of them. If 'cpus_allocating' can work,
there's no need for another. Since I had no way to prove that 'cpus_allocating'
would work, I removed it in V3.

> +	    READ_ONCE(obj_pool_free) > (debug_objects_pool_min_level / 2))
> +		return;
> +
> +	atomic_inc(&cpus_allocating);
>  	while (READ_ONCE(obj_pool_free) < debug_objects_pool_min_level) {
>  		struct debug_obj *new[ODEBUG_BATCH_SIZE];
>  		int cnt;

-- 
Regards,
  Zhen Lei