After upgrading one of my vCenters to 6.0u1 (and subsequently to 6.0u2), I noticed that the vCenter log bundles progressively grew larger and larger. So large that I could no longer upload them to sftpsite.vmware.com through the browser. I had to upload the logs via FTP (which would often timeout).
I asked support if there was a KB for cleaning out old log files, especially the dmp files, but they said no. What I did was I take one of the log bundles and looks for the large directories. These are the two directories with large .dmp or .dmp* files:
C:\ProgramData\VMware\vCenterServer\logs\vmware-vpx\
C:\ProgramData\VMware\VMware VirtualCenter\Logs\
If you look for dmp files in there (some may have dmp.gz or dmp.exe.gz), if you delete them then you will save significant space in your bundle.