El mié, 11-05-2011 a las 14:24 +1200, aaron morton escribió: > What version and what were the values for RecentBloomFilterFalsePositives and > BloomFilterFalsePositives ? > > The bloom filter metrics are updated in SSTableReader.getPosition() the only > slightly odd thing I can see is that we do not count a key cache hit a a true > positive for the bloom filter. If there were a lot of key cache hits and a > few false positives the ratio would be wrong. I'll ask around, does not seem > to apply to Hectors case though. > > Cheers
0.7.5, and I am no longer using key cache. I get the bloom filter stats via jmx. BloomFilterFalsePositiveRatio is always stuck at 1.0. RecentBloomFilterFalsePositiveRation fluctuates from 0 to 1.0 with no intermediate values. As for the index interval settings, I changed it from 128 to 256 and memory consumption was just a tad lower but read performance was worse by a few ms, so not much to gain there. > ----------------- > Aaron Morton > Freelance Cassandra Developer > @aaronmorton > http://www.thelastpickle.com > > On 11 May 2011, at 10:38, Chris Burroughs wrote: > > > On 05/10/2011 02:12 PM, Peter Schuller wrote: > >>> That reminds me, my false positive ration is stuck at 1.0, so I guess > >>> bloom filters aren't doing a lot for me. > >> > >> That sounds unlikely unless you're hitting some edge case like reading > >> a particular row that happened to be a collision, and only that row. > >> This is from JMX stats on the column family store? > >> > > > > (From jmx) I also see BloomFilterFalseRatio stuck at 1.0 on my > > production nodes. The only values that RecentBloomFilterFalseRatio had > > over the past several minutes were 0.0 and 1.0. While I can't prove > > that isn't accurate, it is very suspicions. > > > > The code looked reasonable until I got to SSTableReader, which was too > > complicated to just glance through. >
