Reply from Dan Gibson:
Tourmaline is a functional transactional memory simulator, which is
intended to have extensible behavior for future expansion. Its
default behavior makes no attempt to model a realistic timing nor
interleaving of transactions -- it simply provides the bare minimum
implentation of atomicity in the most trivial, simulator-magic way
possible -- by literally disabling all (other) processors.
To my knowledge, the released version of tourmaline has never been
used to collect viable research data -- it is a tool intended to
enable warm-up of transactional applications, as well as to
facilitate debugging of transactional applications seperate from the
debugging of the timing simulator.
If you are interested in looking at running concurrent threads, you
should look into implementing sub-classes of TransactionController,
which Tourmaline uses to guarantee atomicity of transactions. There
is a how-to guide in the README for tourmaline, called the
'Transaction Controller Cookbook'.
Please note that the /timing/ runs for the LogTM family of work all
used Ruby, not Tourmaline. However, tourmaline is a viable tool for
(much) longer simulations at the cost of some timing fidelity.
Regards,
Dan
On Sep 28, 2007, at 3:37 AM, horsnelm@xxxxxxxxxxxx wrote:
Hi,
I've been looking at the code inside the tourmaline TM module of
the gems
package. I'm trying to run some benchmarks, in particular the
stamp-0.9.4
benchmarks, and wondered if you could comment on the scheduling
policy and
how you have used tourmaline, or gems in general, to generate your
results.
I can see in the tourmaline code, that when you begin a transaction
you
disable interrupts in the processor registers, which means that
until the
transaction resolves it cannot be interrupted. You switch back on
interrupts when the transaction commits or aborts.
Is it not the case that the operating system threads will
interleave with
the transactions, competing for the cpu time? Do you prevent this from
happening by changing the scheduling policy in the OS, or do you
measure
your results in some other manner? The reason I ask, is that when
running
say a 4 threaded application, on a 4 cpu architecture, transactions
infrequently overlap as they are scheduled according to the OS.
Ideally
I'd like the transactional threads to run as concurrently as
possible to
look at the interactions between them.
Thanks,
Matt Horsnell
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