On Mon, Nov 30, 2015 at 02:13:32PM -0500, Waiman Long wrote: > >This would only work if the structure itself is allocated with cacheline > >alignment, and looking at sched_create_group(), we use a plain kzalloc() > >for this, which doesn't guarantee any sort of alignment beyond machine > >word size IIRC. > > With a RHEL 6 derived .config file, the size of the task_group structure was > 460 bytes on a 32-bit x86 kernel. Adding a ____cacheline_aligned tag > increase the size to 512 bytes. So it did make the structure a multiple of > the cacheline size. With both slub and slab, the allocated task group > pointers from kzalloc() in sched_create_group() were all multiples of 0x200. > So they were properly aligned for the ____cacheline_aligned tag to work.
Not sure we should rely on sl*b doing the right thing here. KMALLOC_MIN_ALIGN is explicitly set to sizeof(long long). If you want explicit alignment, one should use KMEM_CACHE(). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
