Re: [naviserver-devel] read/write ns_config

[Vlad S. <vl...@cr...>]

Have you run any performance benchmark similar to Tcl array/ns_sets tests?

Zoran Vasiljevic wrote:
> On 22.08.2006, at 22:13, Stephen Deasey wrote:
> 
>> I don't see how you will handle the locking...  :-(
> 
> If you go and get the:
> 
> https://sourceforge.net/tracker/? 
> func=detail&atid=719009&aid=1549952&group_id=130646
> 
> you can inspect the code ans see how I'm doing the locking.
> 
> Essentially (in a nutshell) every thread has its own
> private copy of all config parameters it requested so far.
> There is also a shared configuration, holding ALL known
> config parameters.
> 
> Under normal circumstances, a reader will go to the shared
> config for a parameter only once: first time it fetches the
> param. All other accesses to the same param are done in
> the local (per-thread) cache. The cache is locked in order
> to synchtonize with the writer thread.
> 
> A writer thread will update the shared config and then walk
> private configs of all theads (which registered themselves
> for a given section - see above) and update them one by one,
> locking each as it goes.
> 
> Since I expect writers to be *far* less active, the reader
> will almost always succeed in locking the private cache.
> Hence, almost no locking contention!
> 
> A bad scenario can happen if you have numerous threads
> reading the same parameter at the same time. Then
> you will get contention on the shared config mutex. But
> this is normally not going to happen in real life, and if
> it happens it will be a very short interval as after that
> all will be cached per-thread privately.
> 
> I believe this is pretty good. It uses some more memory
> but avoids locking contention at maximum.
> 
> What do you think?
> 
> Cheers
> Zoran
> 
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Vlad Seryakov
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