MRG Realtime FAQ

No, since the same compiler tools and runtime environment are preserved from standard Red Hat Enterprise Linux 5, complete compatibility is assured. You can use the exact same applications from a standard Red Hat Enterprise Linux 5 environment.

No. The realtime capabilities are implemented in the kernel - and preserve the same system call interface as standard Red Hat Enterprise Linux. In effect, the realtime enhancements are under the hood providing more precise and predictable levels of low-latency determinism. Having said that, the MRG Realtime is fundamentally a kernel feature, and is therefore incapable of addressing fundamental application level flaws. In other words MRG Realtime is not a panacea for poorly implemented applications.

Yes. No realtime kernel is a panacea. You are still required to perform similar system tuning as is done on standard Red Hat Enterprise Linux. The documentation provided with MRG Realtime includes tuning recommendations.

There are numerous realtime enablers in the Red Hat Enterprise Linux 5 distribution, such as enhancements to the glibc runtime library, PAM library, etc. In short, the technical prerequisites for realtime could not be met in Red Hat Enterprise Linux 4 because the implementation is too old. Hence, there are no plans to provide a Red Hat Enterprise Linux 4 based realtime offering.

Red Hat's objective is to continue the upstream incorporation of realtime capabilities to enable for a common kernel source code base to be used for future releases of both standard and realtime product variants.

Red Hat began the earlier realtime alpha testing on a 2.6.21 baseline which ran quite successfully. Later, rebasing to 2.6.22 was considered, however through our first-hand experience in the large volume of users of Fedora test releases, it became apparent that 2.6.22 had a variety of stability issues. Among them were the shakeout of the new Completely Fair Scheduler (CFS) which was early in its maturity cycle. Given that Red Hat engineers are the authors of the new upstream scheduler Red Hat is in an ideal position to evaluate its product readiness. Aside from CFS, there were other instabilities in 2.6.22. More recently, given our extensive test regiment, combined with the external testing of partners (such as IBM's realtime Java group) and involved customers - there wasn't enough time to rebase to 2.6.23 and get it hardened. It is likely that in later maintenance updates that we may rebase to a newer kernel version - but only after it proves product worthy in our collective testing.

No, the set of kernel changes required for realtime are too large and invasive to backport to the Red Hat Enterprise Linux 5 kernel. This is why Red Hat is productizing MRG Realtime - to provide customers access to new capabilities in advance of the next major release.

Unfortunately not. The latency tracer has dependencies on numerous other MRG Realtime enhancements.

Absolutely. Red Hat continues to advance the capabilities of MRG Realtime. There will be periodic updates, which are likely to include rebasing to more recent upstream kernels to be able to take advantage of new features. For example, Red Hat is currently completing the upstream implementation of a new kernel scheduler called CFS - the Completely Fair Scheduler. This improves the priority handling of realtime processes. CFS is likely to be delivered in a future update to MRG Realtime.

Contact your Red Hat sales representative. Realtime system support is based on customer demand and testing participation by the hardware providers.

Not necessarily. Realtime certification has additional requirements as outlined in the Supported Hardware section.

Since no recompilation is required to run on MRG Realtime, complete application compatibility with standard Red Hat Enterprise Linux 5 is preserved. Hence there are no technical compatibility issues. Red Hat is working with our ISV partners to raise their awareness and confirm support for their applications when run with MRG Realtime. Expect to see an upcoming list of 3rd party ISVs endorsing the realtime platform.

MRG Realtime provides a deterministic and fast basis for MRG Messaging and MRG Grid to offer capabilities like deterministic, low latency messaging and optimized environments for grid tasks. Red Hat is highly optimizing the other parts of Red Hat Enterprise MRG for MRG Realtime.