On Wed, Aug 14, 2013 at 02:55:34PM +0900, Minchan Kim wrote: > This patch moves zsmalloc under zram directory because there > isn't any other user any more. > > Before that, description will explain why we have needed custom > allocator. > > Zsmalloc is a new slab-based memory allocator for storing > compressed pages. It is designed for low fragmentation and > high allocation success rate on large object, but <= PAGE_SIZE > allocations. One things zsmalloc will probably have to address before Andrew deems it worthy is the "memmap peekers" issue. I had to make this change in zbud before Andrew would accept it and this is one of the reasons I have yet to implement zsmalloc support for zswap yet. Basically, zsmalloc makes the assumption that once the kernel page allocator gives it a page for the pool, zsmalloc can stuff whatever metatdata it wants into the struct page. The problem comes when some parts of the kernel do not obtain the struct page pointer via the allocator but via walking the memmap. Those routines will make certain assumption about the state and structure of the data in the struct page, leading to issues. My solution for zbud was to move the metadata into the pool pages themselves, using the first block of each page for metadata regarding that page. Andrew might also have something to say about the placement of zsmalloc.c. IIRC, if it was going to be merged, he wanted it in mm/ if it was going to be messing around in the struct page. Seth -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>