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Monday 18 February 2019

Faster vlan(4) forwarding?

Two years ago we observed that vlan(4) performances suffered from the locks added to the queueing API. At that time, the use of SRP was also pointed out as a possible responsible for the regression. Since dlg@ recently reworked if_enqueue() to allow pseudo-drivers to bypass the use of queues, and their associated locks, let's dive into vlan(4) performances again.

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Monday 21 August 2017

Faster forwarding

Since a couple of months processing incoming IP packets on OpenBSD no longer requires the KERNEL_LOCK(). The first consequence is an improved latency of the system but apparently it also made packet forwarding 20% faster.

At least that's what Hrvoje Popovski measured by the time of the commit, and more recently on his Xeon box (E5-2643 v2 @ 3.50GHz, 3500.44 MHz). When he performed some tests for the vlan(4) regression, he measured on his machine a throughput of 1.42Mpps. Last week, with a -current kernel he measured a throughput of 1.75Mpps.

Yes, it is a bit more than 20%. Yes, the stack is still mostly single-threaded.