----- Original Message ----- > From: "Alexandre Montplaisir" <[email protected]> > To: "Daniel Thibault" <[email protected]>, > [email protected] > Sent: Thursday, October 3, 2013 11:54:15 AM > Subject: Re: [lttng-dev] Making 32-bit user-space events on a 64-bit Linux > system > > >> The Debian/Ubuntu packages for liblttng-ust and liburcu are > >> multiarch-enabled, so you can install the :i386 and :amd64 versions in > >> parallel. That way they will be tracked by the package manager, and won't > >> "linger around". > > Except that the Ubuntu LTTng packages are hopelessly behind right now. > > I wanted to do everything with the 2.3.0 release. > > The packages from the official repo are often behind, yes. But we have > an Ubuntu PPA which follows the stable releases: > https://launchpad.net/~lttng/+archive/ppa > > It's updated daily with the contents of the stable-* git branches. > > > On a different note, why does LTTng have 32- and 64-bit consumers > > anyway? The only possible difference between a 32-bit tracer and a > > 64-bit tracer is that the latter could generate event record fields that > > are 64-bit longs and floats, while the former cannot (but will never > > have to, since the application it is tracing won't have such beasts > > anyway).
No, this is not it at all. 32-bit apps can generate 64-bit integers too, and double-precision floats. The difference between 32 and 64-bit consumers mainly comes for atomic operations: on 64-bit, consumer and application can interact through atomic operations on 64-bit integers, which allow detection of free-running counter overflow much larger than with 32-bit counter. Thanks, Mathieu So the 64-bit consumer should be backward compatible with the > > 32-bit consumer, because it deals with a super-set of the 32-bit consumer > > requirements. If this were the only difference, LTTng would not > > need a separate 32-bit consumer daemon. Is there some sort of > > context-switching overhead associated with a 64-bit daemon accessing a > > buffer that exists in a 32-bit process context? The performance gain would > > justify the existence of a 32-bit consumer, I suppose. > > The consumer shares memory space with the traced process, so they have > to use the same ABI. If they talked only through let's say a pipe, that > wouldn't be necessary, but performance would indeed be much worse. > > > Cheers, > Alex > > _______________________________________________ > lttng-dev mailing list > [email protected] > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
