Changes between Initial Version and Version 1 of WinMulticore

Timestamp:

Oct 25, 2019, 3:27:21 PM (5 years ago)

Author:

davea

Comment:

--

WinMulticore

@@ +1 @@
+= Supporting Windows computers with > 64 cores =
+
+On Windows machines with > 64 cores,
+the cores are divided into "processor groups".
+A given process runs in a particular process group,
+inherited from its parent.
+
+Docs on this:
+
+https://docs.microsoft.com/en-us/windows/win32/procthread/processor-groups
+
+https://docs.microsoft.com/en-us/windows/win32/procthread/what-s-new-in-processes-and-threads
+
+https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-setprocessaffinitymask
+
+Unpleasant, but we're stuck with it.
+
+Currently, the client doesn't do anything related to processor groups,
+and apps run in processor group 0.
+This means that on (say) a 256-core machine,
+BOINC will run 256 single-threaded apps,
+but they'll all run on the same 64 cores.
+This is bad.
+
+Proposed development:
+
+== Phase 0 ==
+
+On startup, get and print processor group info.
+
+== Phase 1 ==
+
+As the client runs apps, it assigns them to a processor group,
+and keeps track of how many free cores each processor group has.
+The assignment policy: run the app in the group that has enough free cores,
+and for which the number of free cores is smallest.
+This will tend to run multicore apps in their own process groups,
+and sequential apps in other groups.
+
+Note: the server doesn't know about processor groups.
+It may send jobs that want to use 256 cores.
+These will end up running as 256 threads on 64 cores.
+
+== Phase 2 ==
+
+Send processor group info to the server,
+which can use it to set the # of threads for multicore apps.
+
+== Notes ==
+
+ * We're not going to use processor affinity.
+  If a job runs in a processor group,
+  its affinity mask is all the processors in that group.
+
+* It's possible for applications to create threads in multiple processor groups,
+  e.g. to use all 256 cores.
+  For now, we'll assume that applications don't do this.