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

From: Vlastimil Babka
Date: Thu Jul 28 2022 - 12:10:30 EST


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@xxxxxxxxx>

Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>

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),