Software trace cache

We explore the use of compiler optimizations, which optimize the layout of instructions in memory. The target is to enable the code to make better use of the underlying hardware resources regardless of the specific details of the processor/architecture in order to increase fetch performance. The Software Trace Cache (STC) is a code layout algorithm with a broader target than previous layout optimizations. We target not only an improvement in the instruction cache hit rate, but also an increase in the effective fetch width of the fetch engine. The STC algorithm organizes basic blocks into chains trying to make sequentially executed basic blocks reside in consecutive memory positions, then maps the basic block chains in memory to minimize conflict misses in the important sections of the program. We evaluate and analyze in detail the impact of the STC, and code layout optimizations in general, on the three main aspects of fetch performance; the instruction cache hit rate, the effective fetch width, and the branch prediction accuracy. Our results show that layout optimized, codes have some special characteristics that make them more amenable for high-performance instruction fetch. They have a very high rate of not-taken branches and execute long chains of sequential instructions; also, they make very effective use of instruction cache lines, mapping only useful instructions which will execute close in time, increasing both spatial and temporal locality.Peer ReviewedPostprint (published version

A Comparison of Query Execution Speeds for Large Amounts of Data Using Various DBMS Engines Executing on Selected RAM and CPU Configurations

In modern economies, most important business decisions are based on detailed analysis of available data. In order to obtain a rapid response from analytical tools, data should be pre-aggregated over dimensions that are of most interest to each business. Sometimes however, important decisions may require analysis of business data over seemingly less important dimensions which have not been pre-aggregated during the ETL process. On these occasions, the ad-hoc "online" aggregation is performed whose execution time is dependent on the overall DBMS performance. This paper describes how the performance of several commercial and non-commercial DBMSs was tested by running queries designed for data analysis using "ad-hoc" aggregations over large volumes of data. Each DBMS was installed on a separate virtual machine and was run on several computers, and two amounts of RAM memory were allocated for each test. Measurements of query execution times were recorded which demonstrated that, as expected, column-oriented databases out-performed classical row-oriented database systems