Schmidt2008experimental question 1 by lebo

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CSCI 6966 Advanced Semantic Web (Fall 2008)

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• Lesson 1, Lesson 2, Lesson 3, Lesson 4, Lesson 5, Lesson 6,
• Lesson 7, Lesson 8, Lesson 9, Lesson 10, Lesson 11, Lesson 12, Lesson 13

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A Question from Tim Lebo about schmidt2008experimental:

The only place the ratios of usr, sys, and total response times are mentioned is in the discussion for Q1 ("Return the year of publication of 'Journal 1 (1940)'", where the authors state, "The gap between total and usr+sys for 25M indicates that much time is spent in waiting for data being read from or written to disk". The choice to use different vertical scales in Figures 1-3 leads to an investigation of these ratios while obscuring a natural consideration of the more important issue: the relative response times between triple store approaches. Regardless, the ratio usr/sys falls within one of three categories: minority/majority, all/none, and none/none -- and the ratio's category transitions from none/none, to all/none, to minority/majority as the data size increases within a condition.

1. What does the ratio of usr and sys times indicate with respect to the performance of the query execution?

Jesse Weaver RDF Management Approaches

Question Modification

Thanks for pointing out that the ratios are skewed due to the log scale. In that case, my entire question might be moot :~0

The Answer from Michael Schmidt

When usr+sys is much smaller than total time this typically indicates that disc access dominates the evaluation time (of course we need to be careful here, since experiments were run on a Duo Core). This is exactly what we wanted to show in this particular scenario.

usr is the sum of usr times from the client and server process, and sys is the sum of the sys times from the client and server process (see "we provide the sum of the usr and sys times of the client and server processes" in the experimental section). Client time was typically negligible, so principally all values are very similar to server usr and server sys time.