Re: [PATCH 6/6] vhost_net: don't poll on -EFAULT
On 04/16/2012 03:16 PM, Michael S. Tsirkin wrote:
On Mon, Apr 16, 2012 at 02:08:33PM +0800, Jason Wang wrote:Currently, we restart tx polling unconditionally when sendmsg() fails. This would cause unnecessary wakeups of vhost wokers as it's only needed when the socket send buffer were exceeded.Why is this a problem?
This issue is when guest driver is able to hit the -EFAULT, vhost discard the the descriptor and restart the polling. This would wake vhost thread and repeat the loop again which waste cpu.
Another possible solution is don't discard the descriptor.
Fix this by restart the tx polling only when sendmsg() returns value other than -EFAULT. Signed-off-by: Jason Wang<jasowang@xxxxxxxxxx> --- drivers/vhost/net.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 29abd65..035fa95 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -262,7 +262,8 @@ static void handle_tx(struct vhost_net *net) UIO_MAXIOV; } vhost_discard_vq_desc(vq, 1); - tx_poll_start(net, sock); + if (err != -EFAULT) + tx_poll_start(net, sock); break; } if (err != len)-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
-- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
[Linux Kernel Discussion] [Ethernet Bridging] [Linux Wireless Networking] [Linux Bluetooth Networking] [Linux Networking Users] [VLAN] [Git] [IETF Annouce] [Linux Assembly] [Security] [Bugtraq] [Photo] [Singles Social Networking] [Yosemite Information] [MIPS Linux] [ARM Linux Kernel] [ARM Linux] [Linux Virtualization] [Linux Security] [Linux IDE] [Linux RAID] [Linux SCSI] [Free Dating]