Dear David,

mu12 is an "autonamed" mutex. The ability of naming (and profiling) of mutexes is a feature of NaviServer (partly inherited from aolServer). When no explicit names are provided to mutexes, these are autonamed and show up like "mu12", which is actually the 12th mutex created on your server.

The order and number of mutexes depend on the config file, so these can't be compared easily cross configurations. However, mu12 is a rather low number, so there is a certain hope that it will be the same on my system. On my test sytems mu12 is used for serializing calls to Tcl_CreateInterp() since this call is not thread-safe (maybe this has changed in the newest tcl8.6 versions).

I am not too confident, that this mutex is the same as on your system, since Tcl_CreateInterp() just creates an empty Tcl interpreter, which should not take long and it should not happen so often. Please check with the updated version from the repository, whether the name has changed and we are actually talking about a contention of the same mutex.

all the best
-g

Am 07.07.16 um 11:43 schrieb David Osborne:
I was wondering if someone could help us understand this Mutex Lock output from nsstats.

It's ordered by Contention and it would seem the figures for mu12, and to a lesser extent, nsd:pool:<server>, are quite high.

I don't know what mu12 is used for. Could someone give an example of the sort of workload which could result in such a high level of contention for this mutex?

Inline images 1

Thanks in advance for any pointers.
--
David


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