Hi, Hanoch Are you talking about i40 VF's latency? And you are using DPDK PF as host driver?
In this case, we are setting the Interrupt Throttling (ITR) to be maximum. That is to say, if the packet rate is very slow , the receive descriptor is written back when ITR timeout, otherwise it is written back when cache line is full (4 descriptors/packets). I think that's why you saw the latency is varying. If we change the ITR to minor, then huge number of interrupts will coming to core which impact performance. Thanks Jingjing From: Hanoch Haim (hhaim) [mailto:hh...@cisco.com] Sent: Friday, November 24, 2017 7:25 PM To: dev@dpdk.org Cc: Wu, Jingjing <jingjing...@intel.com> Subject: RE: [dpdk-dev] net/i40e: latency issue due fix interrupt throttling setting in PF Re-sending Hanoh From: Hanoch Haim (hhaim) Sent: Monday, November 20, 2017 5:19 PM To: dev@dpdk.org<mailto:dev@dpdk.org> Cc: Wu, Jingjing (jingjing...@intel.com<mailto:jingjing...@intel.com>); Hanoch Haim (hhaim) Subject: [dpdk-dev] net/i40e: latency issue due fix interrupt throttling setting in PF Hi All, While integrating dpdk17.11 into TRex latest code a new latency issue is observed (i40e is very sensitive because it has very good resolution due to Qos configuration). git bitsec found the following commit. With this commit we observe high spikes of Rx latency (~40usec) vs (~8usec). Any idea why? I can send how to reproduce this, it is very simple. cfd662d22e7bddb4ba41dbd1384f8497f38c2b4e is the first bad commit commit cfd662d22e7bddb4ba41dbd1384f8497f38c2b4e Author: Jingjing Wu <jingjing...@intel.com<mailto:jingjing...@intel.com>> Date: Thu Aug 24 09:57:51 2017 +0800 net/i40e: fix interrupt throttling setting in PF As no matter the PF host driver is DPDK or other kernel drivers, they are sharing the same virtchnnl interfaces to communicate to VFs. To follow the generic interface, DPDK PF need to set Interrupt Throttling (ITR) index according to the rxitr_idx from virtchnnl instead of ITR_NONE. Fixes: 6d59e4ea74a6 ("net/i40e: change version number to support Linux VF") Cc: sta...@dpdk.org<mailto:sta...@dpdk.org> Signed-off-by: Jingjing Wu <jingjing...@intel.com<mailto:jingjing...@intel.com>> Thanks, Hanoh
