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Description of problem: gdm-user-switch needs too much CPU


Version-Release number of selected component (if applicable): 2.28.2-5.el6.x86_64


How reproducible: 100%


Steps to Reproduce:
1. create password file with many entries
2. login
3. run top or ps
  
Actual results: gdm-user-switch takes almost 100% CPU time for quite a long time.


Expected results: less greedy gdm-user-switch


Additional info: I made tests with various sized /etc/passwd files:

# entries   CPU minutes
2000        ~1
4000        ~4:37
8000        ~20:46

This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release.  Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release.  This request is not yet committed for
inclusion.

*** This bug has been marked as a duplicate of bug 598483 ***