Hi, I experienced high CPU usage in avahi-deamon when a lot of services are announced in the network. This results more than 30 seconds of saturated CPU after queries when ~300 services are present. This also leads to DBUS timeouts in connected clients in some cases.
Using oprofile, I traced the CPU usage to avahi_unescape_label() and (to some extent) avahi_utf8_valid(). From reading the source, and analyzing gdb backtraces, it looks like avahi_unescape_label() is used at many places, and calls avahi_utf8_valid() just before the return. The unescape function copies a source string to a destination string byte-by-byte most of the time. Label strings received over the network are stored unmodified, and every time they are used, avahi_unescape_label() is used. For example, when getting queries with a lot of known answers, domain_equal() is used for comparison, resulting in a big load of avahi_unescape_label() invocations while contructing and queueing the response. avahi_unescape_label() is also used for simple validity checks using assert() (over and over again for the same string), and to split domains into their parts by stopping when a dot is found. So it is somewhat multi-purpose, making it more difficult to replace. From my point of view, there is no easy fix for this. I think the labels should be stored unescaped when they are received to make comparisons more lightweight and making most of the validity checks superfluous. At last, some questions: Am I wrong with my obervation? If not, is this a known issue? Was this already discussed in the past? Are there already any efforts rework the string handling? Regards, Tino Mettler ----- Unsere Datenschutzerklärung finden Sie hier (https://www.lawo.com/de/website/company/rechtliches/datenschutz.html). See our Privacy Policy here (https://www.lawo.com/en/website/company/legal/data-protection.html). _______________________________________________ avahi mailing list avahi@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/avahi
