On Tue, Dec 15, 2015 at 07:21:03PM +0800, Ming Lei wrote: > kmalloc() is often a bit time-consuming, also > one atomic counter has to be used to track the total > allocated elements, which is also not good. > > This patch pre-allocates element pool in htab_map_alloc(), > then use percpu_ida to allocate one slot from the pool, > then the runtime allocation/freeing cost can be decreased. > > From my test, at least 10% fio throughput is improved in block > I/O test when tools/biolatency of bcc(iovisor) is running. > > Signed-off-by: Ming Lei <tom.leim...@gmail.com>
Looks very intersting as well. Approach looks good. If you can make a common allocation helper for this map and for blk-mq would be even better. > - htab->elem_size = sizeof(struct htab_elem) + > - round_up(htab->map.key_size, 8) + > - htab->map.value_size; > + htab->elem_size = round_up(sizeof(struct htab_elem) + > + round_up(htab->map.key_size, 8) + > + htab->map.value_size, > + cache_line_size()); this rounding to cache line is great for performance, but it's extra memory upfront which may not be needed. The per-allocation is a classic performance vs memory trade-off. In other cases it may hurt. So could you change the patch to do pre-allocation only when requested by user space via extra flag for hash map or via new BPF_MAP_TYPE_HASH_PREALLOC type? Not sure yet whether flag or new type is better. I guess implementation will dictate. PS Glad that you found iovisor/tools/biolatency useful. It's indeed pretty helpful to analyze real-time block io latency. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
