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Diffstat (limited to 'Documentation/core-api')
| -rw-r--r-- | Documentation/core-api/memory-allocation.rst | 49 |
1 files changed, 23 insertions, 26 deletions
diff --git a/Documentation/core-api/memory-allocation.rst b/Documentation/core-api/memory-allocation.rst index dcf851b4520f..e47d48655085 100644 --- a/Documentation/core-api/memory-allocation.rst +++ b/Documentation/core-api/memory-allocation.rst @@ -88,10 +88,10 @@ Selecting memory allocator ========================== The most straightforward way to allocate memory is to use a function -from the :c:func:`kmalloc` family. And, to be on the safe side it's -best to use routines that set memory to zero, like -:c:func:`kzalloc`. If you need to allocate memory for an array, there -are :c:func:`kmalloc_array` and :c:func:`kcalloc` helpers. +from the kmalloc() family. And, to be on the safe side it's best to use +routines that set memory to zero, like kzalloc(). If you need to +allocate memory for an array, there are kmalloc_array() and kcalloc() +helpers. The maximal size of a chunk that can be allocated with `kmalloc` is limited. The actual limit depends on the hardware and the kernel @@ -102,29 +102,26 @@ The address of a chunk allocated with `kmalloc` is aligned to at least ARCH_KMALLOC_MINALIGN bytes. For sizes which are a power of two, the alignment is also guaranteed to be at least the respective size. -For large allocations you can use :c:func:`vmalloc` and -:c:func:`vzalloc`, or directly request pages from the page -allocator. The memory allocated by `vmalloc` and related functions is -not physically contiguous. +For large allocations you can use vmalloc() and vzalloc(), or directly +request pages from the page allocator. The memory allocated by `vmalloc` +and related functions is not physically contiguous. If you are not sure whether the allocation size is too large for -`kmalloc`, it is possible to use :c:func:`kvmalloc` and its -derivatives. It will try to allocate memory with `kmalloc` and if the -allocation fails it will be retried with `vmalloc`. There are -restrictions on which GFP flags can be used with `kvmalloc`; please -see :c:func:`kvmalloc_node` reference documentation. Note that -`kvmalloc` may return memory that is not physically contiguous. +`kmalloc`, it is possible to use kvmalloc() and its derivatives. It will +try to allocate memory with `kmalloc` and if the allocation fails it +will be retried with `vmalloc`. There are restrictions on which GFP +flags can be used with `kvmalloc`; please see kvmalloc_node() reference +documentation. Note that `kvmalloc` may return memory that is not +physically contiguous. If you need to allocate many identical objects you can use the slab -cache allocator. The cache should be set up with -:c:func:`kmem_cache_create` or :c:func:`kmem_cache_create_usercopy` -before it can be used. The second function should be used if a part of -the cache might be copied to the userspace. After the cache is -created :c:func:`kmem_cache_alloc` and its convenience wrappers can -allocate memory from that cache. - -When the allocated memory is no longer needed it must be freed. You -can use :c:func:`kvfree` for the memory allocated with `kmalloc`, -`vmalloc` and `kvmalloc`. The slab caches should be freed with -:c:func:`kmem_cache_free`. And don't forget to destroy the cache with -:c:func:`kmem_cache_destroy`. +cache allocator. The cache should be set up with kmem_cache_create() or +kmem_cache_create_usercopy() before it can be used. The second function +should be used if a part of the cache might be copied to the userspace. +After the cache is created kmem_cache_alloc() and its convenience +wrappers can allocate memory from that cache. + +When the allocated memory is no longer needed it must be freed. You can +use kvfree() for the memory allocated with `kmalloc`, `vmalloc` and +`kvmalloc`. The slab caches should be freed with kmem_cache_free(). And +don't forget to destroy the cache with kmem_cache_destroy(). |
