On Tue, May 11, 2010 at 16:07, Matt Mackall wrote: > On Tue, 2010-05-11 at 16:03 -0400, Mike Frysinger wrote: >> 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. > > Make your own slab cache with the alignment flag set, as Pekka already > mentioned. and like i said, that doesnt sound like a reasonable solution when every single SPI driver (over 100 atm) out there is affected -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