I thought that a common default on Linux was to block if /dev/random was to block if the pool of random data was emptied. Refer to http://en.wikipedia.org/?title=/dev/random for a description.
I thought that /dev/urandom did not block if the pool of random data was emptied. That same article describes the differences between the two. I've seen cases with some versions of Java and some Linux variants where Java performance suffered badly when I had emptied the pool of random data. I think that is why Stephen recommends using /dev/urandom so that your program won't block while waiting for random data. Mark Waite On Tue, Jul 29, 2014 at 10:44 PM, Dean Yu <[email protected]> wrote: > Obviously, going from 1.509.4 to 1.554.3 is a pretty big jump that > included lots and lots of changes. However, the fact that the singular act > of downgrading that library got us back to our prior build times is a big > smoking gun to me. > > > I wonder if something changed upstream... > > From the upstream release notes: > > > build217, 2013-06-03: > > - Support for SSH agent based authentication. > > build216, 2013-03-04: > > - Support of unencrypted entries in the known_hosts file. > - Improved timeout handling. > > > BTW you are using /dev/./urandom as an entropy source for the JVM? > > Nope. Should we? > > -- Dean > > > From: Stephen Connolly <[email protected]> > Reply-To: "[email protected]" <[email protected] > > > Date: Tuesday, July 29, 2014 at 2:16 PM > To: "[email protected]" <[email protected]> > Subject: Re: SSH slave performance degradation > > * KK's changes to window sizes should have *increased* performance > * My connection bug fixes were surgical IIRC > * Nicolas's merge of upstream seems to include an EOL change, so hard to > see what changed there with the Github diff tool: > https://github.com/jenkinsci/trilead-ssh2/compare/trilead-ssh2-build214-jenkins-3...trilead-ssh2-build217-jenkins-5 > > I wonder if something changed upstream... > > BTW you are using /dev/./urandom as an entropy source for the JVM? > > > On 29 July 2014 19:51, Dean Yu <[email protected]> wrote: > >> Hi folks, >> We just upgraded our cluster from 1.509.4 to 1.554.3, and discovered a >> significant increase in our build times. Builds that typically took ~50 to >> complete started taking ~90 minutes to finish, sometimes spiking to 2 >> hours. While researching, we found this JIRA[1] which reported that >> downgrading the trilead-ssh2 jar solved the performance issues. >> While this ticket talks specifically artifact downloads, we see that >> our builds as a whole were slower. >> The trilead-ssh2 dependency version was updated by [2], so it was >> introduced into 1.536, show would only have made it to LTS with 1.554.1 in >> April. >> Looking at the trilead-ssh2 repo[3], it looks like there were a small >> set of changes: >> - changes by ndeloof to merge a newer upstream (build214 to build217) >> - changes by stephenc to fix connection bugs >> - changes by kohsuke to support package window sizes >> >> Anyone have thoughts on the likely culprit? Given the severity of the >> performance hit we took, I'm surprised that more people haven't reported >> this. >> >> -- Dean >> >> [1] https://issues.jenkins-ci.org/browse/JENKINS-20550 >> [2] >> https://github.com/jenkinsci/jenkins/commit/bb265c5e95b0fe39128720b903914236962db41b >> [3] https://github.com/jenkinsci/trilead-ssh2/commits/master >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Jenkins Developers" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/d/optout. >> > > -- > You received this message because you are subscribed to the Google Groups > "Jenkins Developers" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "Jenkins Developers" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- Thanks! Mark Waite -- You received this message because you are subscribed to the Google Groups "Jenkins Developers" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
