Performance Analysis and Optimization of the Hurricane File System ...

CHAPTER 6. MICROBENCHMARKS – OTHER FUNDAMENTAL OPERATIONS 60
results in Section 6.3.1. The files were regular, random-access files 5 and the initial pool of block cache entries
was set to 200 instead of the default of 20. All threads were executed in parallel and each was assigned its
own processor and disk.
The results, shown in Figure 6.17, are similar to the results for the file name lookup experiment in
Section 6.3.1. Scalability was poor beyond 2 processors.
6.4.4 Stat with Name Lookup, All Optimizations
This experiment examined the impact of implementing all optimizations in the getAttribute() with name
lookup workload. This configuration included all the optimizations we used previously. The results, shown
in Figure 6.18 and Figure 6.19, indicate that scalability was good but not ideal since it took twice as long
for each thread to execute on 12 processors than on 1 processor. The results were very similar to the results
in Section 6.3.2 that examine the optimized name lookup operation, indicating that the name lookup portion
of the task was the rate limiting component where as the getAttribute() portion scaled well, as shown in
Section 6.4.2. The 8 processor results exhibited the same anomaly as described in Section 5.5.7, resulting in
the lower error bar in the graph. Fortunately, performance trends show that thread execution times appear
to stabilize from 8 processors onwards.
6.4.5 Summary
The optimizations implemented from the file read experiments were applicable to the file stat operation of the
file system. File stat scalability was improved drastically. Ideal scalability was achieved in the getAttribute()
portion of the task, whereas the name lookup portion performed relatively well but did not achieve ideal
scalability.
6.5 Regular File Write Test
This section examines the scalability of the write operation on regular, random-access-based files. Each
thread sequentially writes a 4,096,000 byte regular, random-access-based file to its own disk while running
on its own processor. The operation causes meta-data to accumulate in the caches. The flushing of the
caches to disk was disabled to measure ideal file writing conditions. No optimizations were implemented
for this initial base test. The results, shown in Figure 6.20, indicate that scalability was poor beyond
2 processors, closely mirroring the results of the unoptimized regular file read experiment in Section 5.5.1.
5 In terms of the actions taken by the file system during the getAttribute() operation, there is no difference between extentbased
or regular, random-access files. Consequently, either file types can be used for the getAttribute experiments.