K42: Building a Complete OS Orran Krieger, Marc Auslander, Bryan Rosenburg, Robert Wisniewski, Jimi Xenidis, Dilma Da Silva, Michal Ostrowski, Jonathan Appavoo, Maria Butrico, Mark Mergen, Amos Waterland, Volkmar Uhlig http://www.research.ibm.com/K42
K42: Building a Complete OS. Orran Krieger , Marc Auslander, Bryan Rosenburg, Robert Wisniewski, Jimi Xenidis, Dilma Da Silva, Michal Ostrowski, Jonathan Appavoo, Maria Butrico, Mark Mergen, Amos Waterland, Volkmar Uhlig http://www.research.ibm.com/K42. How it all started. - PowerPoint PPT Presentation
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K42: Building a Complete OS
Orran Krieger, Marc Auslander, Bryan Rosenburg, Robert Wisniewski, Jimi Xenidis, Dilma Da Silva,
Michal Ostrowski, Jonathan Appavoo, Maria Butrico, Mark Mergen, Amos Waterland, Volkmar Uhlig
http://www.research.ibm.com/K42
How it all started
Our Predictions 1996
• Microsoft Windows will dominate• Large-scale SMMP increasingly important• Within 5 years multi-core pervasive• Traditional OS structures not maintainable • Customizability and extensibility critical• Within 5 years 64-bit pervasive
Sufficient motivation to design entirely new OS.
Small aggressive research team.
Resulting K42 Goals• performance/scalability:
– up to large MP and large applications– down for small-scale MP and small apps on large-scale MP
• flexibility/customizability: – policies/implementations of resource instances can be customized to
application needs– system can adapt without penalizing common case performance
• applicability– full functionality with multiple personalities– support client to embedded to server
• wide availability– release open source and build community– highly maintainable/extensible structure
• enable problem domain experts• re-enable architectural innovation• re-enable OS research community
• Framework per service designed to:– Separate mechanism/policy that can be independently customized.– Application or agents can determine which implementation to use
for workload.
• Dynamic customizations: patches/updates, adaptive algorithms, specializing common case, monitoring, application optimizations– Hot swapping: replacing O1 with O2 to adapt to new demands– Dynamic upgrade: replace all objects of a type
Massive investment in/on Linux• In late 90s Linux appeared to be taking off & we abandoned
multiple personalities• Linux API/ABI compatibility largely in library, exceptions:
– Server code for process groups, ptys…– Fork has had way too pervasive impact on kernel MM (we violated our
programming style).• Support both unmodified glibc via trap reflection, and
modified glibc.• Applications with specialized needs can reach past Linux
personality, e.g., to instantiate object, handle events…• We are also compatible with Linux kernel modules, including
device drivers, FS & TCP/IP stack:– Tracking Linux is an ongoing nightmare
Bad predictions, mistakes and questions
Our Predictions 1996
Microsoft Windows will dominate Wasted huge amount of time on multiple personality support.
Large-scale SMMP increasingly important.– True, but much slower than expected.– Massive investment in HW:
• allows existing OSes to run reasonably well• Makes SMMP not cost effective
Within 5 years multi-core pervasive– Only common today, not compelling differentiator until now
Traditional OS structures not maintainable. Customizability and extensibility critical
Within 5 years 64-bit pervasive.– Only common today, this has been a huge barrier to building community
Mistakes/Questions• We should have had a 32-bit version. • Application manager was a bad idea, we totally missed on
virtualization:– Gets rid of the device driver nightmare– Can deploy new OS to solve subset of problem.
• While user-level implementation & micro-kernel clean, continuous challenge & orthogonal to OO design
• We implemented fork wrong!!!• OO design, and infrastructure, obscures control flow:
– Much more difficult for Linux hacker to gain broad understanding.– Requires more sophisticated debugging tools.
• Does OO really help maintainability?
Concluding remarks
The good news• High degree of functionality:
– 32 & 64 bit apps, support standard gentoo tree, MPI. – Applications/benchmarks include SPEC SDET, ReAIM, SPECfp,
many HPC apps (DARPA & DOE)– Recently provided enough support to run commercial JVM (J9)
and DB2. • Object-oriented design has advantages...
– have found special casing easy– hot-swapping simpler than adaptive algorithm– Clustered objects relatively simple to do– local fixes, publish interface not structure– Domain experts/students can easily develop specialized
component. • Have been able to work around global policies, e.g.,
paging.
The good news• General performance monitoring infrastructure key to
identifying problems.• We achieved excellent base performance (although since
degraded); can compensate for intrinsic overheads: – advantages of Linux's hierarchical page tables: exception level traversal,
identify PT entry for fast unmap and avoid segment unmapping, aggressive fork pre-mapping for anonymous memory
multi-core makes design more relevant than at any time in project history.
• Most of IBM team no longer have K42 as day job, but are still passionate about it:– We continue to be excited to support community.– We are actively soliciting people to take over parts of the system.