On Tue, 18 Jan 2011, Beckmann, Brad wrote:
Hi Nilay,
My plan is to tackle the functional access support as soon as I check in
our current group of outstanding patches. I'm hoping to at least check
in the majority of them in the next couple of days. Now that you've
completed the CacheMemory access changes, you may want to re-profile
GEM5 and make sure the next performance bottleneck is routing network
messages in the Perfect Switch. In particular, you'll want to look at
rather large (16+ core) systems using a standard Mesh network. If you
have any questions on how to do that, Arka may be able to help you out,
if not, I can certainly help you. Assuming the Perfect Switch shows up
as a major bottleneck (> 10%), then I would suggest that as the next
area you can work on. When looking at possible solutions, don't limit
yourself to just changes within Perfect Switch itself. I suspect that
redesigning how destinations are encoded and/or the interface between
MessageBuffer dequeues and the PerfectSwitch wakeup, will lead to a
better solution.
Brad
Hi Brad,
I was thinking about the design of the PerfectSwitch. I have at least one
very simple optimization (just need to add one character to
PerfectSwitch.cc). But then, the gains are not that much (about 1% for
the particular instance that I saw).
Do you think most of the messages that are sent out have a single
destination? I am not sure if that statement is clear. What I want to say
is that whether the number of destinations where a message needs to be
delievered is one with a high probability. Can we redesign the routing
table so that instead of being from a mapping from links to destinations,
it maps destinations to links? Or may be we can have both the
representation?
I believe, and this is really my belief (no empirical evidence), that most
of the time is spent in going through all the links, setting values that
would not be used at all and checking whether a link can route to a
destination or not.
Suppose most of the messages are to be delivered to a single destination.
Then, with the redesigned routing table, we only look at the links that
can route to that destination and then choose one adaptively or otherwise.
What do you think?
--
Nilay
_______________________________________________
m5-dev mailing list
m5-dev@m5sim.org
http://m5sim.org/mailman/listinfo/m5-dev
