linux-kernel - mm: some questions about mm/mempool.c

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Date:	Thu, 10 Dec 2015 13:02:44 +0000
From:	"Wang, Zhi A" <zhi.a.wang@...el.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: mm: some questions about mm/mempool.c

Hi Gurus:

Currently we met some allocation failed in mempool_resize() ->

        /* Grow the pool */
        new_elements = kmalloc_array(new_min_nr, sizeof(*new_elements),  // <---- Here
                                     GFP_KERNEL);
        if (!new_elements)
                return -ENOMEM;

My questions:
1. It looks like in the pool creation path, the allocation of pool->elements is done by

mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
                               mempool_free_t *free_fn, void *pool_data,
                               gfp_t gfp_mask, int node_id)
{
        mempool_t *pool;
        pool = kzalloc_node(sizeof(*pool), gfp_mask, node_id);
        if (!pool)
                return NULL;
        pool->elements = kmalloc_node(min_nr * sizeof(void *),
                                      gfp_mask, node_id);

but in the mempool_resize() path, the pool->elements is allocated by kmalloc_array() without  NUMA aware.  Is it correct?

And I think perhaps a vzalloc here may be more reasonable, as the amount of pool->elements may be large and kmalloc here may fail.

2. Shall we need a mempool_refill() function that can recharge the pool at a certain time?

Thanks,
Zhi.
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