Re: [RFC][PATCH] inline a few tiny functions in init/initramfs.c

[Nick Piggin <nickpiggin@yahoo.com.au>]

Con Kolivas wrote:

>On Sat, 24 Sep 2005 09:26, Jesper Juhl wrote:
>
>>A few functions in init/initramfs.c are so simple that I don't see why
>>*any* point in them having to bear the cost of a function call.
>>Wouldn't something like the patch below make sense ?
>>
>
>>-static void __init *malloc(size_t size)
>>+static inline void __init *malloc(size_t size)
>> {
>> 	return kmalloc(size, GFP_KERNEL);
>>
>
>maybe it looks like it would, but kmalloc looks like this:
>
>85 static inline void *kmalloc(size_t size, int flags)
>86 {
>87         if (__builtin_constant_p(size)) {
>88                 int i = 0;
>89 #define CACHE(x) \
>90                 if (size <= x) \
>91                         goto found; \
>92                 else \
>93                         i++;
>94 #include "kmalloc_sizes.h"
>95 #undef CACHE
>96                 {
>97                         extern void __you_cannot_kmalloc_that_much(void);
>98                         __you_cannot_kmalloc_that_much();
>99                 }
>100 found:
>101                 return kmem_cache_alloc((flags & GFP_DMA) ?
>102                         malloc_sizes[i].cs_dmacachep :
>103                         malloc_sizes[i].cs_cachep, flags);
>104         }
>105         return __kmalloc(size, flags);
>106 }
>
>which is not a one liner to inline at all
>
>

Actually, this is even better, because the inline 'malloc' should be
able to propogate the builtin_constantness of 'size' while an out of
line version cannot.

IMO the best policy is not to second guess the API implementor's
choice of inline / noinline. That is - if kmalloc was too big to
inline then it should be fixed in kmalloc or another interface
introduced.

Nick


Send instant messages to your online friends http://au.messenger.yahoo.com