> > 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
Nope not really > currently using JVM_OPTS="$JVM_OPTS -XX:MaxGCPauseMillis=500", even if i > > increase heap to lets say 2GB is that effective b/c young GC's will kick > in > > more frequently to complete in 500ms right ?? > Min heap size for G1 is probably 16G. You were saying "new_heap", now > you're just saying heap - do you mean new here, or total heap size? Apologies, what i mean is new_heap. > > > You tablestats show a max partition size of 75M, which isn't nearly as bad > as I was expecting (or not nearly as bad as we often see when people ask > this question). You do occasionally scan a lot of sstables (up to 20?), so > I'm assuming you have STCS - you may benefit from switching to LCS to try > to limit the number of sstables you touch on read. Also, if your data isn't > in memory (if your data set is larger than RAM and reads are random), you > may benefit from a much lower compression_chunk_size - the default is 64k, > but 4k or 16k is often much better if you do have to read from disk. probably i have to try decreasing chunk size as LCS will not suit as we are write heavy On Fri, Jul 7, 2017 at 7:13 PM, Jeff Jirsa <jji...@apache.org> wrote: > > > On 2017-07-07 07:26 (-0700), Pranay akula <pranay.akula2...@gmail.com> > wrote: > > Lately i am seeing some select queries timing out, data modelling to > blame > > for but not in a situation to redo it. > > > > Does increasing heap will help ?? > > > > currently using 1GB new_heap, I analysed the GC logs not having any > issues > > with major GC's . > > > > Using G1GC , does increasing new_heap will help ?? > > > > Increasing new heap size generally helps when you're seeing a lot of > promotion - if you're not seeing long major GCs, are you seeing a lot of > promotion from eden to old gen? > > You don't typically set -Xmn (new heap size) when using G1GC > > > > currently using JVM_OPTS="$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 > >
