** Description changed:

  I have a ssd/hdd system where the ssd is used for the system and most of
  home is on a large hdd.
  
  I noticed that the weekly fstrim cron job slows the system down considerable, 
including e.g. firefox and
  the desktop. iotop reports:
  """
  otal DISK READ :       0.00 B/s | Total DISK WRITE :       0.00 B/s
  Actual DISK READ:       0.00 B/s | Actual DISK WRITE:       7.71 K/s
-  TID  PRIO  USER     DISK READ  DISK WRITE  SWAPIN     IO>    COMMAND         
 
+  TID  PRIO  USER     DISK READ  DISK WRITE  SWAPIN     IO>    COMMAND
  24504 be/4 root        0.00 B/s    0.00 B/s  0.00 % 99.99 % fstrim --all
  """
  
  So hardly any real io activity but still massive slowdown with
  3.16.0-24-generic.
  
  E.g. a dpkg operation while fstrim is running:
  """
- # time dpkg -i 2vcard_0.5-3_all.deb 
+ # time dpkg -i 2vcard_0.5-3_all.deb
  real  0m8.221s
  user  0m0.895s
  sys   0m0.671s
  
- # time dpkg -i 2vcard_0.5-3_all.deb 
+ # time dpkg -i 2vcard_0.5-3_all.deb
  real  0m8.215s
  user  0m0.895s
  sys   0m0.705s
  
  # killall fstrim
- # time dpkg -i 2vcard_0.5-3_all.deb 
+ # time dpkg -i 2vcard_0.5-3_all.deb
  real  0m2.023s
  user  0m0.992s
  sys   0m0.703s
  
- # time dpkg -i 2vcard_0.5-3_all.deb 
+ # time dpkg -i 2vcard_0.5-3_all.deb
  real  0m1.709s
  user  0m0.958s
  sys   0m0.738s
  """
  
- This may of course be simply a kernel problem.
+ This may of course be simply a kernel problem but I do get similar
+ result for both 3.16 and 3.13.

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https://bugs.launchpad.net/bugs/1393335

Title:
  fstrim slows down mixed ssd/hdd considerable

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