Hi Julian, Thanks for posting about this. I agree that if this is landing in dpkg+apt upstream, it's reasonable to try to get it into the 18.04 release so that it can be used in later releases without needing a dpkg versioned pre-depends.
If we are to evaluate using zstd as the default compression in 18.10 (or later), I think we need to consider the total install experience, and not just look at the dpkg unpack time. For example: On Mon, Mar 12, 2018 at 11:06:11AM +0100, Julian Andres Klode wrote: > firefox > -------- > 8.80user 3.57system 0:37.17elapsed 33%CPU (0avgtext+0avgdata > 25260maxresident)k > 8inputs+548024outputs (0major+376614minor)pagefaults 0swaps > > 4.52user 3.30system 0:33.14elapsed 23%CPU (0avgtext+0avgdata > 25152maxresident)k > 0inputs+544560outputs (0major+386394minor)pagefaults 0swaps > firefox eatmydata > ----------------------- > 8.79user 2.87system 0:12.43elapsed 93%CPU (0avgtext+0avgdata > 25416maxresident)k > 0inputs+548016outputs (0major+384193minor)pagefaults 0swaps > 4.24user 2.57system 0:08.54elapsed 79%CPU (0avgtext+0avgdata > 25280maxresident)k > 0inputs+544584outputs (0major+392117minor)pagefaults 0swaps Since you don't list binary package names for kernel or libreoffice, I'll look at firefox, which is the obvious one. The archive version of this package is 42MiB in size in bionic. If the zstd version is 6% larger, but takes 4 seconds less time to unpack, this means the total install time (download+unpack) is only improved for the end user if the download speed from the apt source is faster than (44108204 bytes * .06 * 8bits/byte / 4.03s ~=) 5.25Mbps. Have you established that this is a typical effective download speed for Ubuntu users? It's certainly faster than my home connection, though I also use a local mirror to speed up installs. It may be reasonable to expect cloud instances to have this much throughput from their mirrors, and so it might be the sensible choice solely on that basis; I'm just checking that it's been measured. In other words: if we want to make this the default, we should quantify Daniel's remark that he would prefer a 6% faster download over a 10% faster unpack. I think we also need to look at the spread of package size increases. If 6% is typical, are there some packages on the high end (of both absolute package size and relative size increase) that we should exclude from switching to zstd? We should be transparent about our analysis here. Thanks, -- Steve Langasek Give me a lever long enough and a Free OS Debian Developer to set it on, and I can move the world. Ubuntu Developer http://www.debian.org/ slanga...@ubuntu.com vor...@debian.org
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