xen-netback: enable skip_guestrx_thread by default

Given that there's almost no grant ops being done, there's no need to
amortize grant hypercall cost through the guestrx kthread. This option
then skips it enterily (only with staging grants) and gets to remove the
contention on queue->wq and queue->rx_lock.

Exadata chatty select tests show an improvement of 14% as depicted in
the bug.

Orabug: 27125766
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 10de6657cea6f18a3d3f40716c29273e2359cc58..068195c9a91580999c400200c50c9a20e7d813cf 100644 (file)
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -60,7 +60,7 @@ module_param(separate_tx_rx_irq, bool, 0644);
  * this might improve performance on cases where frontend is a
  * copybreak interface or is fully recycling pages.
  */
-bool skip_guestrx_thread;
+bool skip_guestrx_thread = true;
 module_param(skip_guestrx_thread, bool, 0644);
 
 /* The time that packets can stay on the guest Rx internal queue