Hi If there is MSLAB enabled - one is with pool and another is without Pool.
I hope you are using MSLAB without pool in this case. So only when ever there are writes that happen then we create 2MB chunks and write data to them. As and when the chunk is full we keep creating new chunks. So when a memstore snapshot happens then we flush out all those chunks and again we keep creating chunks to continue with writes. So in your case when there are empty regions - ya there won't be any chunk being created. >>since data are removed after configured TTL. Would like to know would that cause unnecessary heap usage? If there is an active write that is happening then the last chunk would be around till that is flushed and cleared off. How long is the TTL? Is it few seconds or minutes where TTL expiry can even happen on the memstore data itself? Regards Ram On Thu, Oct 5, 2017 at 9:25 AM, Stack <[email protected]> wrote: > On Wed, Oct 4, 2017 at 9:42 AM, Subash Kunjupillai <[email protected]> > wrote: > > > As sited in HBase Doc > > <http://archive-primary.cloudera.com/cdh5/cdh/5/hbase-0.98.1 > > -cdh5.1.3/book/regions.arch.html#too_many_regions> > > , I understand that MSLAB of each memstore will occupy 2MB(default) of > the > > region server heap memory. So if there are 2000 regions in my region > > server, > > 3.9GB of my heap would be occupied. > > > > My question is, memory for MSLAB will be allocated as soon as the regions > > come online or only if data is written to memstore? > > > It looks like the latter, lazy allocation on first Cell add. > See HeapMemStoreLAB alloc called out of DefaultMemStore. > > If up for experimenting, you could try running without MSLAB with G1GC > enabled; various report G1GC mitigates need for MSLAB (I've not tried this > myself). > > > > > Because I've a cluster > > where 1000 of empty regions in a table, since data are removed after > > configured TTL. Would like to know would that cause unnecessary heap > usage? > > > > > > > As I read it, it would; the last Chunk allocated in DefaultMemStore would > stick around. > > St.Ack > > > > > > > > > > -- > > Sent from: http://apache-hbase.679495.n3.nabble.com/HBase-User-f4020416 > > .html > > >
