linux-kernel - Re: [PATCH 7/8] mm/swap: Add cache for swap slots allocation

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Date:   Thu, 29 Sep 2016 15:04:03 +0800
From:   "Hillf Danton" <hillf.zj@...baba-inc.com>
To:     <tim.c.chen@...ux.intel.com>,
        "'Andrew Morton'" <akpm@...ux-foundation.org>
Cc:     <dave.hansen@...el.com>, <andi.kleen@...el.com>,
        <aaron.lu@...el.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        "'Huang Ying'" <ying.huang@...el.com>,
        "'Hugh Dickins'" <hughd@...gle.com>,
        "'Shaohua Li'" <shli@...nel.org>,
        "'Minchan Kim'" <minchan@...nel.org>,
        "'Rik van Riel'" <riel@...hat.com>,
        "'Andrea Arcangeli'" <aarcange@...hat.com>,
        "'Kirill A . Shutemov'" <kirill.shutemov@...ux.intel.com>,
        "'Vladimir Davydov'" <vdavydov@...tuozzo.com>,
        "'Johannes Weiner'" <hannes@...xchg.org>,
        "'Michal Hocko'" <mhocko@...nel.org>
Subject: Re: [PATCH 7/8] mm/swap: Add cache for swap slots allocation

On Wednesday, September 28, 2016 1:19 AM Tim Chen wrote
[...]
> +
> +static int alloc_swap_slot_cache(int cpu)
> +{
> +	struct swap_slots_cache *cache;
> +
> +	cache = &per_cpu(swp_slots, cpu);
> +	mutex_init(&cache->alloc_lock);
> +	spin_lock_init(&cache->free_lock);
> +	cache->nr = 0;
> +	cache->cur = 0;
> +	cache->n_ret = 0;
> +	cache->slots = vzalloc(sizeof(swp_entry_t) * SWAP_SLOTS_CACHE_SIZE);
> +	if (!cache->slots) {
> +		swap_slot_cache_enabled = false;
> +		return -ENOMEM;
> +	}
> +	cache->slots_ret = vzalloc(sizeof(swp_entry_t) * SWAP_SLOTS_CACHE_SIZE);
> +	if (!cache->slots_ret) {
> +		vfree(cache->slots);
> +		swap_slot_cache_enabled = false;
> +		return -ENOMEM;
> +	}
> +	return 0;
> +}
> +
[...]
> +
> +static void free_slot_cache(int cpu)
> +{
> +	struct swap_slots_cache *cache;
> +
> +	mutex_lock(&swap_slots_cache_mutex);
> +	drain_slots_cache_cpu(cpu, SLOTS_CACHE | SLOTS_CACHE_RET);
> +	cache = &per_cpu(swp_slots, cpu);
> +	cache->nr = 0;
> +	cache->cur = 0;
> +	cache->n_ret = 0;
> +	vfree(cache->slots);

Also free cache->slots_ret?
Or fold the relevant two allocations into one?
 
> +	mutex_unlock(&swap_slots_cache_mutex);
> +}
> 
thanks
Hillf