|Summary:||kcryptd I/O blockage using encrypted filesystem on LVM|
|Product:||[Fedora] Fedora||Reporter:||Michael Hampton <error>|
|Component:||kernel||Assignee:||Milan Broz <mbroz>|
|Status:||CLOSED RAWHIDE||QA Contact:||Fedora Extras Quality Assurance <extras-qa>|
|Fixed In Version:||Doc Type:||Bug Fix|
|Doc Text:||Story Points:||---|
|Last Closed:||2008-08-26 11:13:14 UTC||Type:||---|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
|Cloudforms Team:||---||Target Upstream Version:|
Description Michael Hampton 2008-06-17 01:34:01 UTC
Description of problem: When using an encrypted filesystem on LVM, whether an encrypted PV or LV, the kernel frequently blocks for long periods of time waiting for I/O. top shows anywhere from 20% to 100% CPU time waiting for I/O. Affected processes freeze for several seconds, up to a minute or more, waiting for even small disk reads/writes. Version-Release number of selected component (if applicable): kernel-188.8.131.52-55.fc9.x86_64 How reproducible: Random Steps to Reproduce: 1. Install Fedora 9 to encrypted PV. 2. Use moderately disk intensive processes such as firefox, thunderbird or liferea. Actual results: Some disk operations take dozens of seconds to complete. Expected results: Disk operations should complete in a reasonable time. Additional info: Issue did not occur with Fedora 8. Help tracking this down would be greatly appreciated.
Comment 1 Dave Jones 2008-06-17 01:45:54 UTC
this is likely another case of the 'firefox fsyncs too much' bug. (it calls fsync every time it updates the history db - ie, each time you view a new page. unfortunatly fsync on ext3 means 'write everything in memory out to disk, not just the data from this process'.
Comment 2 Milan Broz 2008-07-04 16:32:29 UTC
There is commit in 2.6.26 kernel (adding cond_resched()) in dmcrypt code, which should help in this situation. (System still need wait for io to finish, but other running application should be more responsible.)
Comment 3 Milan Broz 2008-08-26 11:13:14 UTC
cond_resched() call is in 2.6.26+ kernels, it should help in some situations. There are still some situations when system will wait for IO - mainly if you have multiple LVs but only one encrypted PV... closing this rahwide, there is already kernel with this patch.