On Sat, Sep 10, 2011 at 3:35 AM, Michael Blizek <michi1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: >> I need to allocate fairly a large piece of memory, about 128KB or >> 256KB. I tried to use kmalloc, and it sometimes fails, but vmalloc in >> this case usually still work. >> But I'm not sure how costly vmalloc is. As far as I know, vmalloc >> needs to change the page table, and thus might need to invalidate TLB. >> It seems quite expensive. If it is, maybe I can allocate memory with >> kmalloc first, and then try to use vmalloc if kmalloc fails. Any >> suggestions? > > If it is at all possible, I would suggest avoiding to allocate more than > PAGE_SIZE (usually 4KB) in one continuous chunk. You can use e.g. > scatterlists (which are basically lists of pointers) if you need a bigger > buffer. Actually, I have seen some problems when allocating large pieces of memory constantly. Occasionally, I see alloc_pages and kmalloc fails to allocate the memory I want. The whole point of allocating a large chunk of memory is to avoid extra memory copy because I need to run decompression algorithms on it. Or memory copy is cheaper? I'm also thinking of using slab allocator. The size of memory I need to allocate can change from 20KB to 128KB. Then I need quite a few slab allocators. Thanks, Da _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
