Hi mark, I tested this option on my setup , same issue happened , I will dig into it , if you want to get info log , there is a workaround, set this option to none: Rocksdb_log = "" Cheers, xinxin -----Original Message----- From: Mark Nelson [mailto:mark.nelson@xxxxxxxxxxx] Sent: Saturday, July 26, 2014 12:10 AM To: Shu, Xinxin; ceph-devel@xxxxxxxxxxxxxxx Subject: Re: First attempt at rocksdb monitor store stress testing Hi Xinxin, I'm trying to enable the rocksdb log file as described in config_opts using: rocksdb_log = <path to log file> The file gets created but is empty. Any ideas? Mark On 07/24/2014 08:28 PM, Shu, Xinxin wrote: > Hi mark, > > I am looking forward to your results on SSDs . > rocksdb generates a crc of data to be written , this cannot be switch off (but can be subsititued with xxhash), there are two options , Option. verify_checksums_in_compaction and ReadOptions. verify_checksums, If we disable these two options , i think cpu usage will goes down . If we use universal compaction , this is not friendly with read operation. > > Btw , can you list your rocksdb configuration? > > Cheers, > xinxin > > -----Original Message----- > From: Mark Nelson [mailto:mark.nelson@xxxxxxxxxxx] > Sent: Friday, July 25, 2014 7:45 AM > To: Shu, Xinxin; ceph-devel@xxxxxxxxxxxxxxx > Subject: Re: First attempt at rocksdb monitor store stress testing > > Earlier today I modified the rocksdb options so I could enable universal compaction. Over all performance is lower but I don't see the hang/stall in the middle of the test either. Instead the disk is basically pegged with 100% writes. I suspect average latency is higher than leveldb, but the highest latency is about 5-6s while we were seeing 30s spikes for leveldb with levelled (heh) compaction. > > I haven't done much tuning either way yet. It may be that if we keep level 0 and level 1 roughly the same size we can reduce stalls in the levelled setups. It will also be interesting to see what happens in these tests on SSDs. > > Mark > > On 07/24/2014 06:13 AM, Mark Nelson wrote: >> 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: ceph-devel-owner@xxxxxxxxxxxxxxx >>> [mailto:ceph-devel-owner@xxxxxxxxxxxxxxx] On Behalf Of Mark Nelson >>> Sent: Thursday, July 24, 2014 7:14 AM >>> To: ceph-devel@xxxxxxxxxxxxxxx >>> 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 >>> -- >>> 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
