linux-kernel - Re: [PATCH v3 08/15] mm/slab_common: kmalloc_node: pass large requests to page allocator

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Date:   Thu, 28 Jul 2022 18:09:27 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Hyeonggon Yoo <42.hyeyoo@...il.com>,
        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>,
        Joe Perches <joe@...ches.com>,
        Vasily Averin <vasily.averin@...ux.dev>,
        Matthew WilCox <willy@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 08/15] mm/slab_common: kmalloc_node: pass large
 requests to page allocator

On 7/12/22 15:39, Hyeonggon Yoo wrote:
> Now that kmalloc_large_node() is in common code, pass large requests
> to page allocator in kmalloc_node() using kmalloc_large_node().
> 
> One problem is that currently there is no tracepoint in
> kmalloc_large_node(). Instead of simply putting tracepoint in it,
> use kmalloc_large_node{,_notrace} depending on its caller to show
> useful address for both inlined kmalloc_node() and
> __kmalloc_node_track_caller() when large objects are allocated.
> 
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@...il.com>

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

Nit below:

> ---
>  v3:
> 	This patch is new in v3 and this avoids
> 	missing caller in __kmalloc_large_node_track_caller()
> 	when kmalloc_large_node() is called.
> 
>  include/linux/slab.h | 26 +++++++++++++++++++-------
>  mm/slab.h            |  2 ++
>  mm/slab_common.c     | 17 ++++++++++++++++-
>  mm/slub.c            |  2 +-
>  4 files changed, 38 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 082499306098..fd2e129fc813 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -571,23 +571,35 @@ static __always_inline __alloc_size(1) void *kmalloc(size_t size, gfp_t flags)
>  	return __kmalloc(size, flags);
>  }
>  
> +#ifndef CONFIG_SLOB
>  static __always_inline __alloc_size(1) void *kmalloc_node(size_t size, gfp_t flags, int node)
>  {
> -#ifndef CONFIG_SLOB
> -	if (__builtin_constant_p(size) &&
> -		size <= KMALLOC_MAX_CACHE_SIZE) {
> -		unsigned int i = kmalloc_index(size);
> +	if (__builtin_constant_p(size)) {
> +		unsigned int index;
>  
> -		if (!i)
> +		if (size > KMALLOC_MAX_CACHE_SIZE)
> +			return kmalloc_large_node(size, flags, node);
> +
> +		index = kmalloc_index(size);
> +
> +		if (!index)
>  			return ZERO_SIZE_PTR;
>  
>  		return kmem_cache_alloc_node_trace(
> -				kmalloc_caches[kmalloc_type(flags)][i],
> +				kmalloc_caches[kmalloc_type(flags)][index],
>  						flags, node, size);
>  	}
> -#endif
>  	return __kmalloc_node(size, flags, node);
>  }
> +#else
> +static __always_inline __alloc_size(1) void *kmalloc_node(size_t size, gfp_t flags, int node)
> +{
> +	if (__builtin_constant_p(size) && size > KMALLOC_MAX_CACHE_SIZE)
> +		return kmalloc_large_node(size, flags, node);
> +
> +	return __kmalloc_node(size, flags, node);
> +}
> +#endif
>  
>  /**
>   * kmalloc_array - allocate memory for an array.
> diff --git a/mm/slab.h b/mm/slab.h
> index a8d5eb1c323f..7cb51ff44f0c 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -273,6 +273,8 @@ void create_kmalloc_caches(slab_flags_t);
>  
>  /* Find the kmalloc slab corresponding for a certain size */
>  struct kmem_cache *kmalloc_slab(size_t, gfp_t);
> +
> +void *kmalloc_large_node_notrace(size_t size, gfp_t flags, int node);
>  #endif
>  
>  gfp_t kmalloc_fix_flags(gfp_t flags);
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 6f855587b635..dc872e0ef0fc 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -956,7 +956,8 @@ void *kmalloc_large(size_t size, gfp_t flags)
>  }
>  EXPORT_SYMBOL(kmalloc_large);
>  
> -void *kmalloc_large_node(size_t size, gfp_t flags, int node)
> +static __always_inline

I don't think we need to inline, compiler should be able to make
kmalloc_large_node(_notrace) quite efficient anyway.

> +void *__kmalloc_large_node_notrace(size_t size, gfp_t flags, int node)
>  {
>  	struct page *page;
>  	void *ptr = NULL;
> @@ -976,6 +977,20 @@ void *kmalloc_large_node(size_t size, gfp_t flags, int node)
>  
>  	return ptr;
>  }
> +
> +void *kmalloc_large_node_notrace(size_t size, gfp_t flags, int node)
> +{
> +	return __kmalloc_large_node_notrace(size, flags, node);
> +}
> +
> +void *kmalloc_large_node(size_t size, gfp_t flags, int node)
> +{
> +	void *ret = __kmalloc_large_node_notrace(size, flags, node);
> +
> +	trace_kmalloc_node(_RET_IP_, ret, NULL, size,
> +			   PAGE_SIZE << get_order(size), flags, node);
> +	return ret;
> +}
>  EXPORT_SYMBOL(kmalloc_large_node);
>  
>  #ifdef CONFIG_SLAB_FREELIST_RANDOM
> diff --git a/mm/slub.c b/mm/slub.c
> index f22a84dd27de..3d02cf44adf7 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -4401,7 +4401,7 @@ void *__do_kmalloc_node(size_t size, gfp_t flags, int node, unsigned long caller
>  	void *ret;
>  
>  	if (unlikely(size > KMALLOC_MAX_CACHE_SIZE)) {
> -		ret = kmalloc_large_node(size, flags, node);
> +		ret = kmalloc_large_node_notrace(size, flags, node);
>  
>  		trace_kmalloc_node(caller, ret, NULL,
>  				   size, PAGE_SIZE << get_order(size),