ext4 random block I/O write performance regression with 3.11 Saucy Kernel
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux (Ubuntu) |
Fix Released
|
Medium
|
Colin Ian King |
Bug Description
Commit e7ea81db5(ext4: restructure writeback path) introduced a performance regression with random writes. Using tools such as bonnie++, writes with dd or even stress testing with tools such as 'stress' one can observe a 10%-20% performance regression.
SRU Justification:
Commit e7ea81db5(ext4: restructure writeback path) introduced a performance regression with random writes. Using tools such as bonnie++, writes with dd or even stress testing with tools such as 'stress' one can observe a 10%-20% performance regression.
Impact:
Write performance is diminished causing a noticeable regression compared to previous released kernels.
Fix:
Two patches are required:
a) upstream fix 9c12a83 which fixes the overly aggressive writing back of pages which ultimulately resulted in more seeking and
less performance.
b) commit aeac589a7 from the dev branch of kernel/
Testcase:
Using stress-ng on a 2 CPU machine run:
stress-ng --hdd 2 --hdd-ops 200000
(see: git://kernel.
With the fix, this consistently runs ~10-20% faster than the non-fixed kernel.
CVE References
Changed in linux (Ubuntu): | |
status: | New → In Progress |
importance: | Undecided → Medium |
assignee: | nobody → Colin King (colin-king) |
Changed in linux (Ubuntu): | |
status: | In Progress → Fix Committed |
bug 1242085 may be a duplicate of this bug.