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Accepted
Brian Bi
Asked: 2014-03-12 21:17:17 +0800 CST

Tracing system calls is slow on a KVM VPS?

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I run a website on a KVM VPS and I noticed that processes appear to run extremely slowly when being traced. For example, I ran ls on my home directory, which contains 72 files and directories.

With strace:

real    0m13.591s
user    0m0.024s
sys     0m6.972s

No particular system call is especially slow, but there is a noticeable (~0.1 s) pause after each one in the strace output.

Without strace:

real    0m0.101s
user    0m0.000s
sys     0m0.068s

I'm not sure whether this is related, but recursively removing large directories is also very slow. For example, I used

rsync -av `mktemp -d`/ dir

and it made extremely slow progress, removing only about 200 files per second. (That's slow, right?)

Is this a bug in KVM? Is there any way I could get my hosting company to fix it?

vps

1 Answers

  1. Best Answer

    Update: I still don't know what the problem was, but rebooting fixed it.

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