xz-utils 5.2.2 with threading support for the compressor is currently in the deferred queue for another 24 hours [0]. Once this version has been built a binNMU of dpkg will pick up the threading support. dpkg will the use the number of online CPUs for compression [1] in a "dpkg-deb -b" invocation. Using more CPUs here increases the required amount of memory. If the buildds start running out of memory during dpkg-deb or start swapping - this might due to this change. There is lzma_stream_encoder_mt_memusage() which could be used to compute the needed memory upfront and then maybe decrease the number of selected CPUs while the memory limit is exceeded [2]. Also dpkg-buildpackage's -j argument could be used as the initial hint instead of number of online CPUs.
Just some thoughts in case something goes wrong :) [0] https://ftp-master.debian.org/deferred.html [1] https://sources.debian.net/src/dpkg/1.18.10/lib/dpkg/compress.c/#L534 [2] https://git.breakpoint.cc/cgit/bigeasy/xz-utils-debian.git/tree/src/xz/coder.c#n273 Sebastian
