From: David S. Miller Date: Wed, 4 Jul 2018 12:30:47 +0000 (+0900) Subject: Merge branch 'vhost_net-Avoid-vq-kicks-during-busyloop' X-Git-Tag: v4.19-rc1~140^2~470 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=f744c4bb5ca59289616c7d583dae6d28268f5486;p=linux.git Merge branch 'vhost_net-Avoid-vq-kicks-during-busyloop' Toshiaki Makita says: ==================== vhost_net: Avoid vq kicks during busyloop Under heavy load vhost tx busypoll tend not to suppress vq kicks, which causes poor guest tx performance. The detailed scenario is described in commitlog of patch 2. Rx seems not to have that serious problem, but for consistency I made a similar change on rx to avoid rx wakeups (patch 3). Additionary patch 4 is to avoid rx kicks under heavy load during busypoll. Tx performance is greatly improved by this change. I don't see notable performance change on rx with this series though. Performance numbers (tx): - Bulk transfer from guest to external physical server. [Guest]->vhost_net->tap--(XDP_REDIRECT)-->i40e --(wire)--> [Server] - Set 10us busypoll. - Guest disables checksum and TSO because of host XDP. - Measured single flow Mbps by netperf, and kicks by perf kvm stat (EPT_MISCONFIG event). Before After Mbps kicks/s Mbps kicks/s UDP_STREAM 1472byte 247758 27 Send 3645.37 6958.10 Recv 3588.56 6958.10 1byte 9865 37 Send 4.34 5.43 Recv 4.17 5.26 TCP_STREAM 8801.03 45794 9592.77 2884 v2: - Split patches into 3 parts (renaming variables, tx-kick fix, rx-wakeup fix). - Avoid rx-kicks too (patch 4). - Don't memorize endtime as it is not needed for now. ==================== Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller --- f744c4bb5ca59289616c7d583dae6d28268f5486