On Mon, Sep 19, 2011 at 09:40:30AM -0400, Becker, Jesse (NIH/NHGRI) [C] wrote:
>On Fri, Sep 16, 2011 at 03:10:27PM -0400, no-re...@cfengine.com wrote:
>>Forum: CFEngine Help
>>Subject: Re: Long running shadow file edits?
>>Author: sauer
>>Link to topic: https://cfengine.com/forum/read.php?3,23516,23520#msg-23520
>>
>>Are there a relatively large number of users being edited? I've noticed that
>>performance seems to drop substantially when looping results in a large
>>number of bundle calls, and assuming $index is a list iterator, that could be
>>related.
>
>I have *not* migrated to 3.2.0 yet. But on my test hosts, version 3.2.0
>seems to be noticiably slower than the current version we are running.
>This is a qualitative measure only--if I get a chance I will try to post
>something quantitaive later.
So I just did some test runs, comparing 3.0.5p1 and 3.2.0. The test rig
is a VMWare guest running Centos 5. I ran the following command with
both versions 5 times:
time strace -c -o out.$ver.$i.txt cf-agent -K
Where "$i" loops {1..5}, and "$ver" is 3.0.5 or 3.2.0, as appropriate.
Looking at the output from 'time', I find these average results (times
in seconds)
3.0.5p1
real 19.764
user 11.217
sys 4.071
3.2.0
real 23.515
user 15.267
sys 3.841
Neither batch of tests had significant outliers, with stdev < 0.4
seconds in all cases.
This backs up what I've observed in my test runs of 3.2.0 taking longer
than under 3.0.5, But note that the system time actually dropped by 5%.
Even more interesting is that there are 16,000 *more* syscalls in 3.2.0,
relative to 3.0.5p1, but the amount of time in syscalls reported by
strace is .316 seconds for v3.2.0 sec compared to .521 seconds for v3.0.5.
Most of the change seems to be in time spent in the clone() syscall.
Under 3.0.5, it's some 31% of the time (.164s), with 79 calls. Under 3.2.0,
it's almost 70% of the time, with 194 calls (.218s).
But as I noted, even with a 34% increase in the nubmer of calls, there
is (according to strace) a 39% drop in the time spent.
--
Jesse Becker
NHGRI Linux support (Digicon Contractor)
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