[ltt-dev] Running first tests and Stats

[Mathieu Desnoyers]

* Fabio Kaminski (fabiokaminski at gmail.com) wrote:
> Hi ,
> 
> Im playing with Urcu , and first thing was to tried the tests.. and source
> of it..
> 
> Read throughtput is very impressive.. really unbeliavable.. :)
> 
> so first of all.. thanks for this amazing initiative.. to create this user
> level library!
> 
> 
> As RCU theoretically mostly uses spinlocks instead of mutexes.. i thought in
> give it a trie..
> 
> and changed the test_urcu to use spinlock.. (the same ones provided by
> pthread library) and made a copy..with original  mutex lock..

Please note that the mutex used in test_urcu.c is not related to RCU at
all. It simply protects the home-made memory allocation.

In this implementation, the RCU pointer update is done with
"rcu_xchg_pointer()", which atomically exchanges the new pointer with
the old one, so no mutex nor spinlock is needed there (especially if you
don't care about reading the content you are replacing).

Mutexes or spinlocks can be used to protect writes one from another.
Mutexes are typically implemented as adaptative spinlocks turning into
mutexes after a few loops, so there should not be much difference
between the spinlocks and the mutexes you are trying to compare (other
than implementation differences).

> in my own tests.. the writes, with low hits,  almost double its values..
> while reads, downgrade just a bit.. (i particularly liked this version :))
> 
> so.. my question is if anyone have tried this..
> 
> and what are the impressions?!

Impact on read throughput caused by changes in memory allocation locking
scheme is quite unexpected. You might want continue experimenting to
find out why this caused this change in performance.

Thanks,

Mathieu

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-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com