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path: root/lib/sqfs/frag_table.c
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2020-06-07Move the fragment deduplication hash table back into the block processorDavid Oberhollenzer
Fragment deduplication really doesn't belong into the public API of the fragment table. Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
2020-05-19Cleanup: move hash table header to include directoryDavid Oberhollenzer
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
2020-04-22Import and use Mesa's hash tableMatt Turner
With `perf record`/`perf report` I saw that 30% of the time was spent in `sqfs_frag_table_find_tail_end` with tar2sqfs for a tarball containing the Gentoo ebuild repository (many thousands of small files). The reason was the bucketing hash table in frag_table.c: too many elements in too few buckets meant lots of walking over the linked lists. This patch replaces that hash table with the hash table implementation from Mesa. Its implementation is more complex (is is an open-addressing, linear-reprobing) hash table, but it is much better suited for the task. On my 4c/8t Skylake, the time to run tar2sqfs drops from 7.5s to less than 3s. CPU usage increases from ~207% to ~356%, presumably indicating an increase in available parallelism due to the removal of the hash table as a bottleneck. The `perf report` profile with this patch shows that the time spent in `sqfs_frag_table_find_tail_end` has dropped from ~30% to 0.01%. Output from ministat: x before + after N Min Max Median Avg Stddev x 20 7.476 7.685 7.5725 7.5615 0.051254268 + 20 2.79 2.901 2.846 2.84475 0.03543842 Difference at 95.0% confidence -4.71675 +/- 0.0282015 -62.3785% +/- 0.241477% (Student's t, pooled s = 0.0440618) I imported only the bits of the hash table implementation that were needed for frag_table.c. Among the changes I made after importing are - removed usage of ralloc, Mesa's recursive memory allocator - Replaced ralloc -> malloc ralloc_free -> free rzalloc_array -> calloc - Removed mem_ctx parameters - Added free()s to the appropriate places (valgrind confirms there are no leaks) - removed _mesa_-prefix from function names Fixes: #40 Signed-off-by: Matt Turner <mattst88@gmail.com>
2020-03-04Add a generic copying mechanism to sqfs_object_tDavid Oberhollenzer
This patch adds a deep-copy callback to sqfs_object_t and removes the copying mechanism from sqfs_compressor_t. This is also interesting for other types. Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
2020-02-12Use a hash table for fragment lookup instead of linear searchDavid Oberhollenzer
Profiling on a sample filesystem determined that fragment deduplication lookups rank third place directly after crc32 and the actual compression. By using a hash table instead of linear search, this time can be reduced drastically. Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
2020-02-12Implement a more explicit object systemDavid Oberhollenzer
Make every dynamically allocated, opaque data structure inherit from a common sqfs_object_t structure with common entry points (e.g. destroy). This removes tons of public API functions and replaces them with a simple sqfs_destroy instead. If semantics of the (until now implicit) object system need to be extended, it can be much more conveniantely done this way. Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
2020-01-26Cleanup: Move fragment deduplication code over to fragment tableDavid Oberhollenzer
This removes further clutter from the data writer. Any future efforts on making fragment by hash lookup faster can focus on that area only and don't clutter the block processor. Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
2020-01-24Add a fragment table primitive to libsquashfsDavid Oberhollenzer
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>