e4defrag has fatal CPU performance bottleneck

Bug #1398434 reported by Karl-Philipp Richter on 2014-12-02
This bug affects 1 person
Affects Status Importance Assigned to Milestone
e2fsprogs (Ubuntu)

Bug Description

During defragmentation of a 5 TB ext4 filesystem with one 600 GB file with current value of 300000 and optimal value of 300 shown by `e4defrag -c`, `e4defrag' seems to suffer from a huge CPU performance bottleneck. Over hours only one CPU core is used (-> no parallelization) and there's almost no I/O during that time <1 % of the underlying device's capabilities.

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: e2fsprogs 1.42.10-1.1ubuntu1
Uname: Linux 3.17.4-031704-generic x86_64
ApportVersion: 2.14.7-0ubuntu8
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Dec 2 16:29:12 2014
SourcePackage: e2fsprogs
UpgradeStatus: No upgrade log present (probably fresh install)

Theodore Ts'o (tytso) wrote :

Please strace the e4defrag process to see if it is spinning in userspace or in the kernel. If it is spinning in the kernel, then it's a kernel bug, not an e2fsrpogs problem. And since you're using a non-Ubuntu kernel, you'll need to take this to the upstream linux-ext4 mailing list.

If it turns out to be a case of spinning in the kernel, what we'll want to know is whether you can easily reproduce the problem, and if so, whether you can give us a kernel stack trace by using magic-sysrq-l and magic-sysrq-t.

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