Hello Jing, I've been using the mirror you've kindly setup for at least a month [0], and it's given me a nice speed boost compared to berlin (I can sometimes max my networking equipment bandwidth at about 12 MiB/s, while with ci.guix.gnu.org it typically tops around 5 MiB/s on the best days).
One place where it is excruciatingly slow though is for checking the availability of the substitutes ("looking for substitutes"), which corresponds to querying the server for .narinfo files; it seems to be on at least a 10x order slower than berlin, perhaps 100x, to the point that I often must 'export GUIX_BUILD_OPTIONS=--substitute-urls=https://ci.guix.gnu.org' to get past a lengthy check when there are many substitutes being looked for. Is there something in the proxy setup that could explain this? From what I remember, the connection is supposed to be reused for multiple queries; perhaps a configuration issue could cause this to not be possible for your mirror? (I'm just speculating reasons that could explain a slowdown). Anyhow, thanks for maintaining it! [0] https://berlin-guix.jing.rocks -- Thanks, Maxim