On 2017-07-07 07:26 (-0700), Pranay akula <pranay.akula2...@gmail.com> wrote: > Lately i am seeing some select queries timing out, data modelling to blame > for but not in a situation to redo it. > > Does increasing heap will help ?? > > currently using 1GB new_heap, I analysed the GC logs not having any issues > with major GC's . > > Using G1GC , does increasing new_heap will help ?? >
Increasing new heap size generally helps when you're seeing a lot of promotion - if you're not seeing long major GCs, are you seeing a lot of promotion from eden to old gen? You don't typically set -Xmn (new heap size) when using G1GC > currently using JVM_OPTS="$JVM_OPTS -XX:MaxGCPauseMillis=500", even if i > increase heap to lets say 2GB is that effective b/c young GC's will kick in > more frequently to complete in 500ms right ?? Min heap size for G1 is probably 16G. You were saying "new_heap", now you're just saying heap - do you mean new here, or total heap size? You tablestats show a max partition size of 75M, which isn't nearly as bad as I was expecting (or not nearly as bad as we often see when people ask this question). You do occasionally scan a lot of sstables (up to 20?), so I'm assuming you have STCS - you may benefit from switching to LCS to try to limit the number of sstables you touch on read. Also, if your data isn't in memory (if your data set is larger than RAM and reads are random), you may benefit from a much lower compression_chunk_size - the default is 64k, but 4k or 16k is often much better if you do have to read from disk. - Jeff --------------------------------------------------------------------- To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org For additional commands, e-mail: user-h...@cassandra.apache.org
