Date: Mon, 31 Aug 2020 22:05:59 +0000 From: bugzilla-noreply@freebsd.org To: net@FreeBSD.org Subject: [Bug 248652] netmap: pkt-gen TX huge pps difference between 11-STABLE and 12-STABLE/CURRENT on ix & ixl NIC Message-ID: <bug-248652-7501-ka9xQdZs8s@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-248652-7501@https.bugs.freebsd.org/bugzilla/> References: <bug-248652-7501@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D248652 --- Comment #9 from Vincenzo Maffione <vmaffione@FreeBSD.org> --- Thanks a lot for the tests. I think the way netmap tx is handled right now needs improvement. As far as I can tell, in your setup TX interrupts are simply not used (ix a= nd ixl seem to use softirq for TX interrupt processing). Your experiments with increasing kern.hz cause the interrupt rate of the OS timer to increase, and therefore causing the iflib_timer() routine to be ca= lled more often. Being called more often, the TX ring is cleaned up (TX credits update) more often and therefore the application can submit new TX packets = more often, hence the improved pps. However, clearly increasing kern.hz is not a viable approach. I think we should try to use a separate timer for netmap TX credits update, using higher resolution (e.g. callout_reset_sbt_on()), and maybe try to dynamically adjust the timer period to become smaller when transmitting at = high rate, and lower when transmitting ad low rate. I'll try to come up with an experimental patch in the next days. --=20 You are receiving this mail because: You are on the CC list for the bug. You are the assignee for the bug.=
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