Then we can just go through the code(fastpath, log) and change it so it
copies config at startup into local variables (as in server.c) if that
particular code does not care about realtime changes. This way it will
be a compromise between locking and performance.
Zoran Vasiljevic wrote:
On 23.08.2006, at 16:17, Vlad Seryakov wrote:
Looking thru the code i see that mostly only fastpath and log uses
NsConfig reads in real time, all others are copy values into local
structures. funny, but these who uses config are performance critical
and will introduce lock contention because thet are figthing for the
same config values.
Another raw/uncooked idea: is it possible to keep changed values
separately, no lock default config as is now and whoever changed value
just keep it in the lock-guarded hash. If i care about locking and
changed value i will check new hash for new value, others who does not
may still use read-only config list.
I do not know how this could work. If thread A changes
ns/some/thing
and thread B is constantly looking up the
ns/some/thing
then the B must always lock to get the value, as A may
be fiddling with it at the same time.
Thread B can of course copy the value in its
private (tsd) copy on the first fetch but
then again, HOW is he going to find out that the
thing was changed by the A in the meantime?
I do not believe you can avoid locking if you want
to have consistent behaviour.
Also, the changes done by thread A would be pretty
meaningless if only A is able to see them...
I do not believe this is worth examining.
As said, locking cannot be avoided. It is just the question
of: can we tolerate it or not? I can. Therefore for me it
is irelevant. But I do not if you can. Therefore I'm looking
to see if we can do this as runtime or compile-time option.
Also, because the locking is needed, we have to see how we
can minimize it, also minimizing time spent in the locked
sections of the code (by speeding up certain operations for
example).
Cheers
Zoran
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