> On Sept. 9, 2016, 2:53 p.m., Gabor Dozsa wrote: > > I like the idea of starting the sync on a pseudo op very much. I cannot see > > the usefulness of stopping the sync after it started though. Do you have a > > use case in mind? > > > > I have a few comments below (mainly minor nits). > > > > However, I think there is also a basic issue with the CPU suspend approach. > > A CPU can wake up whenever there is an interrupt or even a snoop request. > > That should be taken care of somehow I assume.
The use case for switching off would be if you have multiple regions of interest in the code and no need to sync in between. You could also just run the simulation a bunch of times and move the start sync point, but I think it’s much cleaner to run the app once and toggle the sync. I suppose a spurious wakeup is possible; I had not really thought about it. I haven't seen CPUs wakeup in practice, but I don't really have any devices that would generate an interrupt/snoop when all the cores are asleep. One alternative way to do this would be to not suspend any of the cores and modify the sync to support all the devices being on different ticks when sync starts. We would need to remember what the start time was for all the participating nodes and use that time to enforce synchronization instead of assuming everyone is on the same tick. I avoided doing this since suspending the CPUs until we reach the max of all nodes ticks' was easier. - Michael ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: http://reviews.gem5.org/r/3595/#review8713 ----------------------------------------------------------- On Aug. 4, 2016, 4:51 p.m., Michael LeBeane wrote: > > ----------------------------------------------------------- > This is an automatically generated e-mail. To reply, visit: > http://reviews.gem5.org/r/3595/ > ----------------------------------------------------------- > > (Updated Aug. 4, 2016, 4:51 p.m.) > > > Review request for Default. > > > Repository: gem5 > > > Description > ------- > > Changeset 11561:1414a40eb1e2 > --------------------------- > dev: Add m5 op to toggle synchronization for dist-gem5. > This patch adds the ability for an application to request dist-gem5 to begin/ > end synchronization using an m5 op. When toggling on sync, all nodes agree on > the next sync point based on the maximum of all nodes' ticks. CPUs are > suspended until the sync point to avoid sending network messages until sync > has > been enabled. Toggling off sync acts like a global execution barrier, where > all CPUs are disabled until every node reaches the toggle off point. This > avoids tricky situations such as one node hitting a toggle off followed by a > toggle on before the other nodes hit the first toggle off. > > > Diffs > ----- > > configs/common/Options.py 91f58918a76abf1a1dedcaa70a9b95789da7b88c > src/arch/x86/isa/decoder/two_byte_opcodes.isa > 91f58918a76abf1a1dedcaa70a9b95789da7b88c > src/dev/net/Ethernet.py 91f58918a76abf1a1dedcaa70a9b95789da7b88c > src/dev/net/dist_etherlink.cc 91f58918a76abf1a1dedcaa70a9b95789da7b88c > src/dev/net/dist_iface.hh 91f58918a76abf1a1dedcaa70a9b95789da7b88c > src/dev/net/dist_iface.cc 91f58918a76abf1a1dedcaa70a9b95789da7b88c > src/dev/net/dist_packet.hh 91f58918a76abf1a1dedcaa70a9b95789da7b88c > src/dev/net/tcp_iface.hh 91f58918a76abf1a1dedcaa70a9b95789da7b88c > src/dev/net/tcp_iface.cc 91f58918a76abf1a1dedcaa70a9b95789da7b88c > src/sim/pseudo_inst.hh 91f58918a76abf1a1dedcaa70a9b95789da7b88c > src/sim/pseudo_inst.cc 91f58918a76abf1a1dedcaa70a9b95789da7b88c > util/m5/m5op.h 91f58918a76abf1a1dedcaa70a9b95789da7b88c > util/m5/m5op_x86.S 91f58918a76abf1a1dedcaa70a9b95789da7b88c > util/m5/m5ops.h 91f58918a76abf1a1dedcaa70a9b95789da7b88c > > Diff: http://reviews.gem5.org/r/3595/diff/ > > > Testing > ------- > > > Thanks, > > Michael LeBeane > > _______________________________________________ gem5-dev mailing list [email protected] http://m5sim.org/mailman/listinfo/gem5-dev
