[Bug 381300] Re: elevator=cfq (default) cause starvation

[Andrea Bravetti]

** Description changed:

  Binary package hint: linux-image
  
  I had many performance problems using a usb pendrive:
  writing large files cause a system slowdown sometimes unacceptable.
  
  I performed several tests and in the end the culprit was found to
  be the CFQ scheduler which is used by default since 2.6.18...
  
  CFQ may be good on large system (but I'm not sure), but on a desktop
- with one (or two) cpu and only one disk it is unacceptable.
+ with one (or two) cpu and only one disk and some very slow (but usefull)
+ devices it is unacceptable.
  
  If you are unsure try something like "dd if=/dev/zero of=/dev/sdx" where
  /dev/sdx is a 4gb pendrive, then try opening a web page... panic!
  
  No, not "kernel panic" but "user panic" is guaranteed!
  
  Any user that will try ubuntu and need to use a pendrive will
  think that it work like a floppy disk on win95...
  
  For a long time I believed it was a driver problem, but now
  I'm sure it depends on the scheduler, in fact, I resolved it just
  adding "elevator=noop".
  
  If you care the desktop experience, please, consider the possibility
  of moving to elevator=noop, at least for the "desktop" version
  if not for the "server"...
  
  I'm having this problem with any ubuntu version with kernel >= 2.6.18
  and actually I'm on jaunty with karmic's 2.6.30...
  
  A nice lecture:
  http://www.redhat.com/magazine/008jun05/features/schedulers/

** Description changed:

  Binary package hint: linux-image
  
  I had many performance problems using a usb pendrive:
- writing large files cause a system slowdown sometimes unacceptable.
+ writing large files cause a system slowdown (starvation, may be)
+ sometimes unacceptable.
  
  I performed several tests and in the end the culprit was found to
  be the CFQ scheduler which is used by default since 2.6.18...
  
  CFQ may be good on large system (but I'm not sure), but on a desktop
  with one (or two) cpu and only one disk and some very slow (but usefull)
  devices it is unacceptable.
  
  If you are unsure try something like "dd if=/dev/zero of=/dev/sdx" where
  /dev/sdx is a 4gb pendrive, then try opening a web page... panic!
  
  No, not "kernel panic" but "user panic" is guaranteed!
  
  Any user that will try ubuntu and need to use a pendrive will
  think that it work like a floppy disk on win95...
  
  For a long time I believed it was a driver problem, but now
  I'm sure it depends on the scheduler, in fact, I resolved it just
  adding "elevator=noop".
  
  If you care the desktop experience, please, consider the possibility
  of moving to elevator=noop, at least for the "desktop" version
  if not for the "server"...
  
  I'm having this problem with any ubuntu version with kernel >= 2.6.18
  and actually I'm on jaunty with karmic's 2.6.30...
  
  A nice lecture:
  http://www.redhat.com/magazine/008jun05/features/schedulers/

-- 
elevator=cfq (default) cause starvation
https://bugs.launchpad.net/bugs/381300
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