On Wed, Jun 1, 2016 at 2:08 AM, Jianjian Huo <jianjian.huo@xxxxxxxxxxx> wrote: > Hi Haomai, > > I noticed this as well, and made same changes to RocksDBStore in this PR last week: > https://github.com/ceph/ceph/pull/9215 > > One thing which is even worse, seek will bypass row cache, so kv pairs won't be able to be cached in row cache. > I am working to benchmark the performance impact, will publish the results after I am done this week. Oh, cool! I think you can cherry-pick my another leveldb fix. BTW, do you pay an attention to prefix seek api? I think it will be more suitable than column family in ceph case. If we can have well-defined prefix rule, we can make most of range query cheaper! > > Jianjian > > On Tue, May 31, 2016 at 9:49 AM, Haomai Wang <haomai@xxxxxxxx> wrote: >> Hi Sage and Mark, >> >> As mentioned in BlueStore standup, I found rocksdb iterator *Seek* >> won't use bloom filter like *Get*. >> >> *Get* impl: it will look at filter firstly >> https://github.com/facebook/rocksdb/blob/master/table/block_based_table_reader.cc#L1369 >> >> Iterator *Seek*: it will do binary search, by default we don't specify >> prefix feature(https://github.com/facebook/rocksdb/wiki/Prefix-Seek-API-Changes). >> https://github.com/facebook/rocksdb/blob/master/table/block.cc#L94 >> >> So I use a simple tests: >> >> ./db_bench -num 10000000 -benchmarks fillbatch >> fill the db firstly with 1000w records. >> >> ./db_bench -use_existing_db -benchmarks readrandomfast >> readrandomfast case will use *Get* API to retrive data >> >> [root@hunter-node2 rocksdb]# ./db_bench -use_existing_db -benchmarks >> readrandomfast >> >> LevelDB: version 4.3 >> Date: Wed Jun 1 00:29:16 2016 >> CPU: 32 * Intel(R) Xeon(R) CPU E5-2680 0 @ 2.70GHz >> CPUCache: 20480 KB >> Keys: 16 bytes each >> Values: 100 bytes each (50 bytes after compression) >> Entries: 1000000 >> Prefix: 0 bytes >> Keys per prefix: 0 >> RawSize: 110.6 MB (estimated) >> FileSize: 62.9 MB (estimated) >> Writes per second: 0 >> Compression: Snappy >> Memtablerep: skip_list >> Perf Level: 0 >> WARNING: Assertions are enabled; benchmarks unnecessarily slow >> ------------------------------------------------ >> DB path: [/tmp/rocksdbtest-0/dbbench] >> readrandomfast : 4.570 micros/op 218806 ops/sec; (1000100 of >> 1000100 found, issued 46639 non-exist keys) >> >> =========================== >> then I modify readrandomfast to use Iterator API[0]: >> >> [root@hunter-node2 rocksdb]# ./db_bench -use_existing_db -benchmarks >> readrandomfast >> LevelDB: version 4.3 >> Date: Wed Jun 1 00:33:03 2016 >> CPU: 32 * Intel(R) Xeon(R) CPU E5-2680 0 @ 2.70GHz >> CPUCache: 20480 KB >> Keys: 16 bytes each >> Values: 100 bytes each (50 bytes after compression) >> Entries: 1000000 >> Prefix: 0 bytes >> Keys per prefix: 0 >> RawSize: 110.6 MB (estimated) >> FileSize: 62.9 MB (estimated) >> Writes per second: 0 >> Compression: Snappy >> Memtablerep: skip_list >> Perf Level: 0 >> WARNING: Assertions are enabled; benchmarks unnecessarily slow >> ------------------------------------------------ >> DB path: [/tmp/rocksdbtest-0/dbbench] >> readrandomfast : 45.188 micros/op 22129 ops/sec; (1000100 of >> 1000100 found, issued 46639 non-exist keys) >> >> >> 45.18 us/op vs 4.57us/op! >> >> The test can be repeated and easy to do! Plz correct if I'm doing >> foolish thing I'm not aware.. >> >> So I proposal this PR: https://github.com/ceph/ceph/pull/9411 >> >> We still can make further improvements by scanning all iterate usage >> to make it better! >> >> [0]: >> --- a/db/db_bench.cc >> +++ b/db/db_bench.cc >> @@ -2923,14 +2923,12 @@ class Benchmark { >> int64_t key_rand = thread->rand.Next() & (pot - 1); >> GenerateKeyFromInt(key_rand, FLAGS_num, &key); >> ++read; >> - auto status = db->Get(options, key, &value); >> - if (status.ok()) { >> - ++found; >> - } else if (!status.IsNotFound()) { >> - fprintf(stderr, "Get returned an error: %s\n", >> - status.ToString().c_str()); >> - abort(); >> - } >> + Iterator* iter = db->NewIterator(options); >> + iter->Seek(key); >> + if (iter->Valid() && iter->key().compare(key) == 0) { >> + found++; >> + } >> + >> if (key_rand >= FLAGS_num) { >> ++nonexist; >> } >> -- >> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
