On Wed, Nov 24, 2010 at 08:05:47PM -0800, Roland Dreier wrote: > > So if you are worried about how many times ib_poll_cq is called then > > bound the kzalloc size and wrap the whole thing in a loop, but > > realistically I have to think the performance trade off of > > kzalloc/free vs calling ib_poll more often is not entirely obvious. > > That's true... maybe doing things one at a time but avoiding the allocs > is the right tradeoff. Hmm, considering your list is everything but Mellanox, maybe it makes much more sense to push the copy_to_user down into the driver - ie a ibv_poll_cq_user - then the driver can construct each CQ entry on the stack and copy it to userspace, avoid the double copy, allocation and avoid any fixed overhead of ibv_poll_cq. A bigger change to be sure, but remember this old thread: http://www.mail-archive.com/linux-rdma@xxxxxxxxxxxxxxx/msg05114.html 2x improvement by removing allocs on the post path.. Jason -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
