Information Technology Reference
In-Depth Information
5 Experimental Results
All experiments were conducted on a Intel Core i7 920 @ 2.67GHz machine with
6 GB RAM, using Eclipse version 3.7 and OpenJDK version 7. The trace files
were generated using LTTng version 0.232. The trace files contain the detailed
execution trace at kernel level, including all the system calls, scheduling events
and interrupts.
5.1 Construction Time
History Tree Construction:
Figure 8 shows the time required to read a trace,
update the attribute tree and transient (current) state, and build the history tree.
The first case is to measure the time taken by the trace reader to only read the
trace events, without passing them to the state provider module. This gives an
idea of the proportion of time taken by each step. As Figure 8 shows, the time
required to write the intervals to the disk-based history tree is an important
factor. A solution to reduce the construction time is using the partial history
update, instead of complete update. In this case, as mentioned previously, the
history database is updated for a group of state changes, instead of each single
state change. The effect of using a partial database update (partial history tree)
on the construction time, storage space and query time is studied in the following
sections.
700
State System + History
Current State, without history
Reading only
LTTV State System
600
500
400
300
200
100
0
0
2000
4000
6000
8000
10000
12000
Size of the original trace (MB)
Fig. 8.
Time for reading the trace and constructing the attribute tree
Partial Tree Update:
Figure 9 shows the time required to store the values in
the history tree in different cases: the case that updates the database for each
single state changes and the case that updates the database partially for each
20,000, 50,000, 100,000 events, respectively.
With a partial history tree, the number of updates to database will be de-
creased during the construction phase, therefore less time is required. Please
note that in all cases, it still requires to inspect each event. For that reason, the
time required for the partial storage cases is almost the same.
