On Tue, May 11, 2010 at 02:42, Pekka Enberg wrote: > On Tue, May 11, 2010 at 9:33 AM, Dmitry Torokhov wrote: >>> what guarantee exactly do you have for that statement ? >> >> The data is kmalloced, kmalloc aligns on cacheline boundary AFAIK which >> means that next kmalloc data chunk will not share "our" cacheline. > > No, there are no such guarantees. kmalloc() aligns on > ARCH_KMALLOC_MINALIGN or ARCH_SLAB_MINALIGN depending on which is > bigger but beyond that, there are no guarantees. You can, of course, > use kmem_cache_create() with SLAB_HWCACHE_ALIGN to align on cacheline > boundary. so how is this to be addressed in general ? this is a problem for any device that does SPI transactions, and having every driver create its own kmem cache isnt the answer. do people need to kmalloc() like 2x the desired size and manually align it themselves ? declaring alignments on struct members doesnt matter if the base of the struct isnt aligned. seems like we need a new GFP flag that says we need a cache aligned pointer so we can give that to kmalloc() and such. -mike -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
