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Review request for Default. Repository: gem5 Description ------- Changeset 10879:f244ad15be32 --------------------------- mem: Delay responses in the crossbar before forwarding This patch changes how the crossbar classes deal with responses. Instead of forwarding responses directly and burdening the neighbouring modules in paying fot the latency (through the pkt->headerDelay), we now queue them before sending them. The coherency protocol is not affected as requests and any snoop requests/responses are still passed on in zero time. Thus, the responses end up paying for any header delay accumulated when passing through the crossbar. Any latency incurred on the request path will be paid for on the response side, if no other module has dealt with it. As a result of this patch, responses are returned at a later point. This affects the number of outstanding transactions, and quite a few regressions see an impact in blocking due to no MSHRs, increased cache-miss latencies, etc. Going forward we should be able to use the same concept also for snoop responses, and any request that is not an express snoop. Diffs ----- src/mem/cache/cache_impl.hh ebb3d0737aa7 src/mem/coherent_xbar.hh ebb3d0737aa7 src/mem/coherent_xbar.cc ebb3d0737aa7 src/mem/noncoherent_xbar.hh ebb3d0737aa7 src/mem/noncoherent_xbar.cc ebb3d0737aa7 src/mem/snoop_filter.hh ebb3d0737aa7 src/mem/xbar.hh ebb3d0737aa7 Diff: http://reviews.gem5.org/r/2887/diff/ Testing ------- Thanks, Andreas Hansson _______________________________________________ gem5-dev mailing list [email protected] http://m5sim.org/mailman/listinfo/gem5-dev
