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Capriccio

A capriccio is a spritely, improvisational musical dance involving multiple voices.

The Capriccio project aims to create tools to ease the burden on programmers who develop high-performance systems software. Our primary goal is to allow high performance without high complexity. Our target applications include clustered Internet servers, databases and OS kernel components. These applications must perform well under a wide range of operating conditions. In particular, they must handle large variations in load gracefully and make maximal use of the available resources. Conventional mechanisms for realizing these goals require very complicated programming logic. This introduces bugs and makes the software difficult to write and maintain.

Approach

The key insight behind Capriccio is that many of the tricks that programmers use to achieve high performance can be automated, either statically or by changing the runtime system. Hence, we are working to achieve the following goals:

Flexible, application-specific user-level threading.

High-performance system software is typified by a large number of concurrent actions. Managing this concurrency is often one of the most difficult and error-prone aspects of high-performance systems programming. Many researchers have argued that event-based programming is the best way to handle high concurrency, as it exposes both scheduling and per-task resource management direclty to the programmer, and allows more taylored programs.

We believe that events are fundamentally more difficult to use than threads, and can cause more errors in the resulting programs. Hence, we have developed a threads package with all of the performance advantgages of events. This threads package forms the core of the Capriccio runtime environment.

Powerful static analysis framework.

Capriccio leverages the powerful static analysis framework provided by CIL and Ccured to deduce important properties of a program at compile time. This information can be used statically to catch bugs and reduce programmer errors. It can also be fed into the runtime system to allow more effecient execution.

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