linux-kernel - Re: [PATCH v2 13/23] mm/slab: kmalloc: pass requests larger than order-1 page to page allocator

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Date:   Wed, 27 Apr 2022 10:10:00 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Hyeonggon Yoo <42.hyeyoo@...il.com>
Cc:     Marco Elver <elver@...gle.com>,
        Matthew WilCox <willy@...radead.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 13/23] mm/slab: kmalloc: pass requests larger than
 order-1 page to page allocator

On 4/14/22 10:57, Hyeonggon Yoo wrote:
> There is not much benefit for serving large objects in kmalloc().
> Let's pass large requests to page allocator like SLUB for better
> maintenance of common code.
> 
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@...il.com>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

Some nits:

> @@ -3607,15 +3607,25 @@ void kmem_cache_free_bulk(struct kmem_cache *orig_s, size_t size, void **p)
>  {
>  	struct kmem_cache *s;
>  	size_t i;
> +	struct folio *folio;
>  
>  	local_irq_disable();
>  	for (i = 0; i < size; i++) {
>  		void *objp = p[i];

folio can be declared here
could probably move 's' too, and 'i' to the for () thanks to gnu11

>  
> -		if (!orig_s) /* called via kfree_bulk */
> -			s = virt_to_cache(objp);
> -		else
> +		if (!orig_s) {
> +			folio = virt_to_folio(objp);
> +			/* called via kfree_bulk */
> +			if (!folio_test_slab(folio)) {
> +				local_irq_enable();
> +				free_large_kmalloc(folio, objp);
> +				local_irq_disable();
> +				continue;
> +			}
> +			s = folio_slab(folio)->slab_cache;
> +		} else
>  			s = cache_from_obj(orig_s, objp);

This should now use { } brackets per kernel style.

> +
>  		if (!s)
>  			continue;
>