On Mon, Jul 17, 2017 at 10:12:12AM +0200, Lennart Poettering wrote: > On Fri, 14.07.17 03:18, vcap...@pengaru.com (vcap...@pengaru.com) wrote: > > > The current hashmap iteration incurs at least one function call per > > iteration, and in my observations using gcc 6.3 w/-g -O2, it's two: > > > > internal_hashmap_iterate() > > hashmap_iterate_entry() > > > > for every element in the hashmap. > > > > In profiles of `journalctl -b --no-pager` having multiple (50) log files, > > the hashmap iteration shows up as ~10% of the CPU in callgrind > > output. > > I wonder if it wouldn't be easiest to simply bypass hashmap native > iteration for this case. i.e. add a linked list for the open journal > files which we can easily traverse in O(1) time? > > The hashmap implementation has been optimized to require very little > memory, because we have so many hashmap/sets around in PID 1. It's not > optimized to make iteration fast though.
See also https://github.com/systemd/systemd/pull/6365: test-hashmap took more than two minutes on rpi3. Zbyszek _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
