I have another guess about how M5 manages duplicated responses:if a broadcast
packet find a response in a snoop port, the pkt is tagged "memInhibit" and
responded to the upper level.Because the pkt is a pointer, memInhibit will be
seen by other ports, and they will no longer respond to that packet.As a
result, there will be no duplicated response. Am I getting the
point?Unfortunately, when modeling the traffic of the interconnection, I have
to duplicate the packets for broadcasting, and there is no guarantee that
packets will probe snoop ports before the dest ports (which was done in
bus::recvTiming). as a result, the memInhibit for one packet won't be seen by
its dulicates, and multiple responses may occur. In this case, I try to ignore
and discard the duplicated packet in Cache<TagStore>::handleResponse, but this
results in other faults. Do you know any way out of this ?Thanks!JiayuanFrom:
[EMAIL PROTECTED]: [EMAIL PROTECTED]: Sun, 9 Dec 2007 14:28:43 +0800Subject:
[m5-users] help with broadcast/snoop handling
Hi all,
I'm modeling the interconnection, when modeling the interconnection and
simulate all the routers, I am following the bus that broadcast a packet to all
the snoop ports if dest is broadcast.
However, I came to this during debugging in timing mode with my
interconnection prototype:
m5.debug: build/ALPHA_SE/mem/cache/miss/mshr.hh:211: MSHR::Target*
MSHR::getTarget(): Assertion `hasTargets()' failed.
triggered in Cache::handleResponse at the statement:
cache_impl.hh:707: MSHR::Target *initial_tgt =
mshr->getTarget();
doing a trace reveals that the broadcast request got two requests
(ReadExResp) from two nodes. (an L1 cache's memSidePort receives response first
from a peer L1's memSidePort, and then from the L2's memSidePort).
Is there any clue on top of your head about how this happens? My guess
is the peer's L1 snoops the packet and found a match, so both the peer L1 and
L2
both responsed the request, the second request got missed in the mshr
because the target has already been fulfilled. What do you think?
Thanks!
Jiayuan
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