On Tue, 7 Jun 2011 18:54:57 +0300, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > On Thu, Jun 02, 2011 at 06:43:25PM +0300, Michael S. Tsirkin wrote: > > This reverts commit 3c1b27d5043086a485f8526353ae9fe37bfa1065. > > The only user was virtio_net, and it switched to > > min_capacity instead. > > > > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > > It turns out another place in virtio_net: receive > buf processing - relies on the old behaviour: > > try_fill_recv: > do { > if (vi->mergeable_rx_bufs) > err = add_recvbuf_mergeable(vi, gfp); > else if (vi->big_packets) > err = add_recvbuf_big(vi, gfp); > else > err = add_recvbuf_small(vi, gfp); > > oom = err == -ENOMEM; > if (err < 0) > break; > ++vi->num; > } while (err > 0); > > The point is to avoid allocating a buf if > the ring is out of space and we are sure > add_buf will fail. > > It works well for mergeable buffers and for big > packets if we are not OOM. small packets and > oom will do extra get_page/put_page calls > (but maybe we don't care). > > So this is RX, I intend to drop it from this patchset and focus on the > TX side for starters. We could do some hack where we get the capacity, and estimate how many packets we need to fill it, then try to do that many. I say hack, because knowing whether we're doing indirect buffers is a layering violation. But that's life when you're trying to do microoptimizations. Cheers, Rusty. -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html