Jeffrey Bosboom jbosboom

ARM’s Scalable Vector Extensions: A Critical Look at SVE2 For Integer Workloads

Scalable Vector Extensions (SVE) is ARM’s latest SIMD extension to their instruction set, which was announced back in 2016. A follow-up SVE2 extension was announced in 2019, designed to incorporate all functionality from ARM’s current primary SIMD extension, NEON (aka ASIMD).

Despite being announced 5 years ago, there is currently no generally available CPU which supports any form of SVE (which excludes the [Fugaku supercomputer](https://www.fujitsu.com/global/about/innovation/

As tested on Linux:

An SCM_RIGHTS ancillary message is "attached" to the range of data bytes sent in the same sendmsg() call.
However, as always, recvmsg() calls on the receiving end don't necessarily map 1:1 to sendmsg() calls. Messages can be coalesced or split.
The recvmsg() call that receives the first byte of the ancillary message's byte range also receives the ancillary message itself.
To prevent multiple ancillary messages being delivered

	# Trying to use the following command and recieving:
	# Error: GDBus.Error:System.Error.ENXIO: No such device or address

	# StartTransientUnit(in s arg_0,
	# in s arg_1,
	# in a(sv) arg_2,
	# in a(sa(sv)) arg_3,
	# out o arg_4);

	gdbus call \