The RAM requirement of ECM tasks can be capped by a command line switch, to be specified in app_config.xml. Example syntax:
-maxmem 2000
for 2 GB. (Needs a proper app_version block and cmdline tags around it.) If the particular task needed more than is allowed by the command line switch, it will still run, but its run time will increase.
(
source in German, see 3rd post. Alas the syntax gets lost in
machine translation. The way how boinc checks for memory consumption is also discussed in this thread.)
Edit 2,
I only remember tasks with up to ~2 GB RAM usage, from the few and brief occasions that I ran yoyo@home. But according to the link above, there had been batches of WUs with up to 10 GB RAM requirement.
Furthermore, I understand from this thread: The server may send you tasks which
individually may need as much RAM as is configured in BOINC in the "Disk and memory" options. While the task runs and is allocating memory, the client should notice and either suspend other tasks, or this task, into "waiting for memory" state. But if the client is not quick enough to check, memory allocations will fail and tasks will crash.
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Edit 1,
concerned parties have opened two threads at the yoyo numbercrunching forum, in order to alert the admin about the impending server load:
https://www.rechenkraft.net/forum/viewtopic.php?f=57&t=16976
https://www.rechenkraft.net/forum/viewtopic.php?f=57&t=16977
However, since RKN, including yoyo, are actively participating in FB sprints, he noticed anyway in the morning.
https://www.rechenkraft.net/forum/viewtopic.php?f=92&t=16857&start=408#p175353