Line 84 is the line where a string parameter is created. I can't see much relation to file uploads (besides perhaps the sync plugin is doing all requests in one PHP call?). Our XML-RPC library isn't optimized for large files, everyone writing code using that library should be aware of that. It might be possible PHP is keeping a number of copies of the data in the RAM. So I vote for won't fix, not a bug. Perhaps the sync plugin can workaround that limitation by e.g. using a more efficient XML-RPC library for file uploads, but that isn't subject of this bug tracker. I've created another bug report for the problem with filenames described in that forum post, it's
FS#1918.