Re: [PATCH 6/6] vhost_net: remove the max pending check
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2013-08-16 10:00:45
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kvm, lkml, virtualization
On Fri, Aug 16, 2013 at 01:16:30PM +0800, Jason Wang wrote:
We used to limit the max pending DMAs to prevent guest from pinning too many pages. But this could be removed since: - We have the sk_wmem_alloc check in both tun/macvtap to do the same work - This max pending check were almost useless since it was one done when there's no new buffers coming from guest. Guest can easily exceeds the limitation. - We've already check upend_idx != done_idx and switch to non zerocopy then. So even if all vq->heads were used, we can still does the packet transmission.
We can but performance will suffer.
quoted hunk ↗ jump to hunk
So remove this check completely. Signed-off-by: Jason Wang <jasowang@redhat.com> --- drivers/vhost/net.c | 13 ------------- 1 files changed, 0 insertions(+), 13 deletions(-)diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index a035a89..ed3f165 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c@@ -38,8 +38,6 @@ MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;" * Using this limit prevents one virtqueue from starving others. */ #define VHOST_NET_WEIGHT 0x80000 -/* MAX number of TX used buffers for outstanding zerocopy */ -#define VHOST_MAX_PEND 128 #define VHOST_GOODCOPY_LEN 256 /*@@ -372,17 +370,6 @@ static void handle_tx(struct vhost_net *net) break; /* Nothing new? Wait for eventfd to tell us they refilled. */ if (head == vq->num) { - int num_pends; - - /* If more outstanding DMAs, queue the work. - * Handle upend_idx wrap around - */ - num_pends = likely(nvq->upend_idx >= nvq->done_idx) ? - (nvq->upend_idx - nvq->done_idx) : - (nvq->upend_idx + UIO_MAXIOV - - nvq->done_idx); - if (unlikely(num_pends > VHOST_MAX_PEND)) - break; if (unlikely(vhost_enable_notify(&net->dev, vq))) { vhost_disable_notify(&net->dev, vq); continue;-- 1.7.1