[Bug 3186] Surprisingly large unshared memory usage

bugzilla-daemon at dp3.samba.org bugzilla-daemon at dp3.samba.org
Wed Nov 23 06:42:00 GMT 2005


------- Comment #2 from vanes002 at umn.edu  2005-11-22 23:41 MST -------
What version are you using?  You have 2.6.7 selected in the bug report, but
that's still in development.

The copy-on-write optimization wasn't done until v2.6.1 (Apr 2004):

    - The generator is now better about not modifying the file list
      during the transfer in order to avoid a copy-on-write memory
      bifurcation (on systems where fork() uses shared memory).
      Previously, rsync's shared memory would slowly become unshared,
      resulting in real memory usage nearly doubling on the receiving
      side by the end of the transfer.  Now, as long as permissions
      are being preserved, the shared memory should remain that way
      for the entire transfer.

You use the -p option, so you meet the "permissions being preserved" condition.

The file_struct data and other chunks of data are allocated out of the free
memory pool.  If lots of those allocated chunks are returned to the pool, pool
management involves memory being modified, so that would require new writes.

Wayne - does rsync free up anything substantial at any time after the fork that
might trigger this?

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