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

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CHAPTER 3. HFS ARCHITECTURE 25 Block cache entry Directory content 1. 2. 3. ¦¦¦¦¦¦¦¦ ¦¦¦¦¦¦¦¦ ¦¦¦¦¦¦¦¦ ¦¦¦¦¦¦¦¦ ¦¦¦¦¦¦¦¦ ¦¦¦¦¦¦¦¦ ¦¦¦¦¦¦¦¦ ¦¦¦¦¦¦¦¦ ¦¦¦¦¦¦¦¦ ¦¦¦¦¦¦¦¦ disk ORS cache entry Partial block index of directory For loading of ORS cache entry, see trace of getAttribute() diagram. Block cache entry Complete block index of directory Figure 3.8: Cache trace of path name lookup. block numbers. It identifies the disk block that contains the packed data and allows it to be loaded into the block cache. 4. If the block index is not found, the block cache is searched a third time but for the file index. The file index identifies the disk block that contains the block index of the packed data file and allows it to be loaded from disk into the block cache. 5. If the file index cannot be found, the indirect file index in the superblock is consulted, which is always resident in memory. At this point in the call chain, the execution is reversed and the missing block cache and ORS cache entries are filled from disk. The indirect file index leads to the direct file index, which leads to the block index of the packed data file. The packed data block cache is filled and the ORS cache extracts the packed data from the block cache to fill the ORS cache entry. The ORS cache now contains the attributes of the target file. The general idea is that in the common case, meta-data is in the caches and that is why the caches are always checked first. If the meta-data is not found in the cache, it is placed into the cache by following the meta-data chain and using that information to access the disk. This is a recursive process that repeats as necessary. The read and write file system operations interact with the cache system in a similar fashion using steps 3, 4, and 5. 3.6.2 Path Name Lookup The path name lookup operation returns a file token identifier for a given path name, such as /usr/bin/diff. The file token, which is similar to an inode number under Berkeley FFS, allows for easy identification of the target file by the file system and is used by clients to identify specific files. The token is a concatenation of the file number, file type, and disk number. The root directory is a well-known file token and this is where the operation begins. The task involves tracing the path name recursively by using the file token of the disk
CHAPTER 3. HFS ARCHITECTURE 26 current path component, such as /, to extract the subsequent file token of the next path component, such as /usr/. The caches are accessed as follows (Figure 3.8): 1. The directory contents of the current path component is acquired from the block cache. The directory contents may occupy several block cache entries and each one is searched until the path name component is found or until the end of the directory contents is reached. 2. If a directory block is not found in the block cache, the ORS cache is searched for the partial directory block index. If the ORS cache entry cannot be found, the procedure for ORS cache miss handling is similar to the previous description of the getAttribute() file system call. The partial directory block index indicates the disk block of the desired directory block and allows it to be loaded from disk into the block cache. 3. If the complete directory block index is required, the block cache is searched. If the index cannot be found, is it loaded from disk and placed into the block cache. The target disk block, which contains the complete directory block index, is indicated in the very last entry of the partial directory block index. Once loaded into the block cache, the complete index can be used to load the appropriate directory content block from disk into the block cache. The above steps are repeated recursively for each component of the directory path until the path name is resolved and the final target file token is found. The getDents() file system call, which returns the contents of a directory rather than the file token of a particular file of directory, interacts with the cache system in a similar fashion. The getAttribute() and path name lookup operations cover most of the important code paths and their traces have demonstrated the role of the meta-data caches and the general operation of HFS.
Page 1 and 2: Performance Analysis and Optimizati
Page 3 and 4: Acknowledgements This thesis has be
Page 5 and 6: 4.6 Measurements Taken and Graph In
Page 7 and 8: List of Tables 3.1 File system inte
Page 9 and 10: 6.1 Create. . . . . . . . . . . . .
Page 11 and 12: CHAPTER 1. INTRODUCTION AND MOTIVAT
Page 13 and 14: CHAPTER 1. INTRODUCTION AND MOTIVAT
Page 15 and 16: CHAPTER 2. BACKGROUND AND RELATED W
Page 23 and 24: Chapter 3 HFS Architecture This cha
Page 25 and 26: CHAPTER 3. HFS ARCHITECTURE 16 3.1.
Page 27 and 28: CHAPTER 3. HFS ARCHITECTURE 18 ORS
Page 29 and 30: CHAPTER 3. HFS ARCHITECTURE 20 dirt
Page 31 and 32: CHAPTER 3. HFS ARCHITECTURE 22 dire
Page 33: CHAPTER 3. HFS ARCHITECTURE 24 1. 2
Page 37 and 38: CHAPTER 4. EXPERIMENTAL SETUP 28 1
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Page 43 and 44: Chapter 5 Microbenchmarks - Read Op
Page 45 and 46: CHAPTER 5. MICROBENCHMARKS - READ O
Page 61 and 62: Chapter 6 Microbenchmarks - Other F
Page 63 and 64: CHAPTER 6. MICROBENCHMARKS - OTHER
Page 75 and 76: Chapter 7 Macrobenchmark 7.1 Purpos
Page 77 and 78: CHAPTER 7. MACROBENCHMARK 68 server
Page 79 and 80: CHAPTER 7. MACROBENCHMARK 70 avg #
Page 81 and 82: CHAPTER 7. MACROBENCHMARK 72 Logica
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CHAPTER 7. MACROBENCHMARK 76 avg #
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CHAPTER 7. MACROBENCHMARK 78 7.5 Ot
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CHAPTER 7. MACROBENCHMARK 80 to deq
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CHAPTER 8. CONCLUSIONS 82 8.1 Gener
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CHAPTER 8. CONCLUSIONS 84 read-only
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Bibliography [1] Gene M. Amdahl. Va
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BIBLIOGRAPHY 88 [33] David Kotz, So
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BIBLIOGRAPHY 90 [71] Keith A. Smith
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Performance Analysis and Optimization of the Hurricane File System ...

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