Hi Xinxin,
Thanks! I wonder as well if it might be interesting to expose the
options related to universal compaction? It looks like rocksdb provides
a lot of interesting knobs you can adjust!
Mark
On 07/24/2014 12:08 AM, Shu, Xinxin wrote:
Hi mark,
I think this maybe related to 'verify_checksums' config option ,when
ReadOptions is initialized, default this option is true , all data read from
underlying storage will be verified against corresponding checksums, however,
this option cannot be configured in wip-rocksdb branch. I will modify code to
make this option configurable .
Cheers,
xinxin
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Mark Nelson
Sent: Thursday, July 24, 2014 7:14 AM
To: [email protected]
Subject: First attempt at rocksdb monitor store stress testing
Hi Guys,
So I've been interested lately in leveldb 99th percentile latency (and the
amount of write amplification we are seeing) with leveldb. Joao mentioned he
has written a tool called mon-store-stress in wip-leveldb-misc to try to
provide a means to roughly guess at what's happening on the mons under heavy
load. I cherry-picked it over to wip-rocksdb and after a couple of hacks was
able to get everything built and running with some basic tests. There was
little tuning done and I don't know how realistic this workload is, so don't
assume this means anything yet, but some initial results are here:
http://nhm.ceph.com/mon-store-stress/First%20Attempt.pdf
Command that was used to run the tests:
./ceph-test-mon-store-stress --mon-keyvaluedb <leveldb|rocksdb>
--write-min-size 50K --write-max-size 2M --percent-write 70 --percent-read 30
--keep-state --test-seed 1406137270 --stop-at 5000 foo
The most interesting bit right now is that rocksdb seems to be hanging in the
middle of the test (left it running for several hours). CPU usage on one core
was quite high during the hang. Profiling using perf with dwarf symbols I see:
- 49.14% ceph-test-mon-s ceph-test-mon-store-stress [.] unsigned int
rocksdb::crc32c::ExtendImpl<&rocksdb::crc32c::Fast_CRC32>(unsigned int, char
const*, unsigned long)
- unsigned int
rocksdb::crc32c::ExtendImpl<&rocksdb::crc32c::Fast_CRC32>(unsigned int, char
const*, unsigned long)
51.70% rocksdb::ReadBlockContents(rocksdb::RandomAccessFile*,
rocksdb::Footer const&, rocksdb::ReadOptions const&, rocksdb::BlockHandle
const&, rocksdb::BlockContents*, rocksdb::Env*, bool)
48.30%
rocksdb::BlockBasedTableBuilder::WriteRawBlock(rocksdb::Slice const&,
rocksdb::CompressionType, rocksdb::BlockHandle*)
Not sure what's going on yet, may need to try to enable logging/debugging in
rocksdb. Thoughts/Suggestions welcome. :)
Mark
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