On Mon, 25 Jul 2016, Tejun Heo wrote: > I don't get it. What's the harm of using percpu memory here? Other > percpu data structures have remote access too. They're to a lower > degree but I don't see a clear demarcation line and making addtions > per-cpu seems to have significant benefits here. If there's a better > way of splitting the list and locking, sure, let's try that but short > of that I don't see anything wrong with doing this per-cpu. For the regular global declarations we have separate areas for "SHARED" per cpu data like this. See DECLARE_PER_CPU_SHARED* and friends. Even if you align a percpu_alloc() there is still the possibility that other percpu variables defined after this will suffer from aliasing. The aligning causes space to be wasted for performance critical areas where you want to minimize cache line usage. The variables cannot be packed as densely as before. I think allocations like this need to be separate. Simply allocate an array of these structs using kcalloc(nr_cpu_ids, sizeof(my_struct), GFP_KERNEL)? Why bother with percpu_alloc() if its not per cpu data? Well if we do not care about that detail that much then lets continue going down this patch. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
