FreeBSD 11.0-RELEASE is just around the corner, and it will be bringing a long list of new features and improvements — far too many for me to list here. But as part of the release process, the FreeBSD release engineering team has built images for Amazon EC2, and as semi-official maintainer of that platform (I've never been appointed to this role, but I've been doing it for years and nobody has told me to stop...) I think there are some improvements in FreeBSD 11.0 which are particularly noteworthy for EC2 users.

First, the EC2 Console Screenshot functionality now works with FreeBSD. This provides a "VGA" output as opposed to the traditional "serial port" which EC2 has exposed as "console output" for the past decade, and is useful largely because the "VGA" output becomes available immediately whereas the "serial port" output can lag by several minutes. This improvement is a simple configuration change — older releases didn't waste time writing to a non-serial console because it didn't go anywhere until Amazon added support on their side — and can be enabled on older FreeBSD releases by changing the line console="comconsole" to boot_multicons="YES" in /boot/loader.conf.

The second notable change is support for EC2 "Enhanced Networking" using Intel 82599 hardware; on the C3, C4, R3, I2, D2, and M4 (excluding m4.16xlarge) families, this provides increased network throughput and reduced latency and jitter, since it allows FreeBSD to talk directly to the networking hardware rather than via a Xen paravirtual interface. Getting this working took much longer than I had hoped, but the final problem turned out not to be in FreeBSD at all — we were tickling an interrupt-routing bug in a version of Xen used in EC2. Unfortunately FreeBSD does not yet have support for the new "Elastic Network Adapter" enhanced networking used in P2 and X1 instance families and the m4.16xlarge instance type; I'm hoping that we'll have a driver for that before FreeBSD 11.1 arrives.

The third notable change is an improvement in EC2 disk throughput. This comes thanks to enabling indirect segment I/Os in FreeBSD's blkfront driver; while the support was present in 10.3, I had it turned off by default due to performance anomalies on some EC2 instances. (Those EC2 performance problems have been resolved, and disk I/O performance in EC2 on FreeBSD 10.3 can now be safely improved by removing the line hw.xbd.xbd_enable_indirect="0" from /boot/loader.conf.)

Finally, FreeBSD now supports all 128 CPUs in the x1.32xlarge instance type. This improvement comes thanks to two changes: The FreeBSD default kernel was modified in 2014 to support up to 256 CPUs (up from 64), but that resulted in a (fixed-size) section of preallocated memory being exhausted early in the boot process on systems with 92 or more CPUs; a few months ago I changed that value to tune automatically so that FreeBSD can now boot and not immediately panic with an out-of-the-box setup on such large systems.

I think FreeBSD/EC2 users will be very happy with FreeBSD 11.0-RELEASE; but I'd like to end with an important reminder: No matter what you might see on FTP servers, in EC2, or available via freebsd-update, the new release has not been released until you see a GPG-signed email from the release engineer. This is not just a theoretical point: In my time as a FreeBSD developer I've seen multiple instances of last-minute release re-rolls happening due to problems being discovered very late, so the fact that you can see bits doesn't necessarily mean that they are ready to be downloaded. I hope you're looking forward to 11.0-RELEASE, but please be patient.

Posted at 2016-10-03 06:00 | Permanent link | Comments
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