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:   Sat, 30 Apr 2022 11:50:28 +0000
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Vlastimil Babka <vbabka@...e.cz>
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 Wed, Apr 27, 2022 at 10:10:00AM +0200, Vlastimil Babka wrote:
> 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
>

Right!

> >  
> > -		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.
> 

Yes. will do both in v3.

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