Avoid seed reuse when --benchmarks has more than one test (#9733)
Summary: When --benchmarks has more than one test then the threads in one benchmark will use the same set of seeds as the threads in the previous benchmark. This diff fixe that. This fixes https://github.com/facebook/rocksdb/issues/9632 Pull Request resolved: https://github.com/facebook/rocksdb/pull/9733 Test Plan: For this command line the block cache is 8GB, so it caches at most 1024 8KB blocks. Note that without this diff the second run of readrandom has a much better response time because seed reuse means the second run reads the same 1000 blocks as the first run and they are cached at that point. But with this diff that does not happen. ./db_bench --benchmarks=fillseq,flush,compact0,waitforcompaction,levelstats,readrandom,readrandom --compression_type=zlib --num=10000000 --reads=1000 --block_size=8192 ... ``` Level Files Size(MB) -------------------- 0 0 0 1 11 238 2 9 253 3 0 0 4 0 0 5 0 0 6 0 0 ``` --- perf results without this diff DB path: [/tmp/rocksdbtest-2260/dbbench] readrandom : 46.212 micros/op 21618 ops/sec; 2.4 MB/s (1000 of 1000 found) DB path: [/tmp/rocksdbtest-2260/dbbench] readrandom : 21.963 micros/op 45450 ops/sec; 5.0 MB/s (1000 of 1000 found) --- perf results with this diff DB path: [/tmp/rocksdbtest-2260/dbbench] readrandom : 47.213 micros/op 21126 ops/sec; 2.3 MB/s (1000 of 1000 found) DB path: [/tmp/rocksdbtest-2260/dbbench] readrandom : 42.880 micros/op 23299 ops/sec; 2.6 MB/s (1000 of 1000 found) Reviewed By: jay-zhuang Differential Revision: D35089763 Pulled By: mdcallag fbshipit-source-id: 1b50143a07afe876b8c8e5fa50dd94a8ce57fc6b
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