Hi All,
Could somebody explain/describe CellCache allocation/eviction policy?
After running random read/write tests, I came to the conclusion that
CellCache operation is very different from what is described in Google
BigTable paper, i.e. CellCache works as a write buffer rather than a
cache. CellCache seems to help a lot for optimizing writes but it
doesn't help reads.
Here are the results:
random_write_test 100000000
Elapsed time: 8.16 s
Total inserts: 100000
Throughput: 12403559.87 bytes/s
Throughput: 12256.48 inserts/s
random_read_test 100000000
Elapsed time: 1038.47 s
Total scanned: 100000
Throughput: 97451.43 bytes/s
Throughput: 96.30 scanned cells/s
Random read speed is ~100x slower than the result in Google BigTable
for random read test which fits in the memory. In this case the data
set size should be ~100MB and should comfortably fit in the DRAM
(8GB).
Also, tcmalloc heap profiling shows that the usage memory actually
decreases to ~50MB during random read test while it is >700MB during
random write test (although top instead shows increase).
I apologize if I am missing something very basic, I have very little
experience in this area.
Thanks,
Alex
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