Is the current reason for a large starting heap due to the memtable? On Thu, Feb 22, 2018 at 4:44 PM, Carl Mueller <carl.muel...@smartthings.com> wrote:
> ... compaction on its own jvm was also something I was thinking about, > but then I realized even more JVM sharding could be done at the table level. > > On Thu, Feb 22, 2018 at 4:09 PM, Jon Haddad <j...@jonhaddad.com> wrote: > >> Yeah, I’m in the compaction on it’s own JVM camp, in an ideal world where >> we’re isolating crazy GC churning parts of the DB. It would mean reworking >> how tasks are created and removal of all shared state in favor of messaging >> + a smarter manager, which imo would be a good idea regardless. >> >> It might be a better use of time (especially for 4.0) to do some GC >> performance profiling and cut down on the allocations, since that doesn’t >> involve a massive effort. >> >> I’ve been meaning to do a little benchmarking and profiling for a while >> now, and it seems like a few others have the same inclination as well, >> maybe now is a good time to coordinate that. A nice perf bump for 4.0 >> would be very rewarding. >> >> Jon >> >> > On Feb 22, 2018, at 2:00 PM, Nate McCall <zznat...@gmail.com> wrote: >> > >> > I've heard a couple of folks pontificate on compaction in its own >> > process as well, given it has such a high impact on GC. Not sure about >> > the value of individual tables. Interesting idea though. >> > >> > On Fri, Feb 23, 2018 at 10:45 AM, Gary Dusbabek <gdusba...@gmail.com> >> wrote: >> >> I've given it some thought in the past. In the end, I usually talk >> myself >> >> out of it because I think it increases the surface area for failure. >> That >> >> is, managing N processes is more difficult that managing one process. >> But >> >> if the additional failure modes are addressed, there are some >> interesting >> >> possibilities. >> >> >> >> For example, having gossip in its own process would decrease the odds >> that >> >> a node is marked dead because STW GC is happening in the storage JVM. >> On >> >> the flipside, you'd need checks to make sure that the gossip process >> can >> >> recognize when the storage process has died vs just running a long GC. >> >> >> >> I don't know that I'd go so far as to have separate processes for >> >> keyspaces, etc. >> >> >> >> There is probably some interesting work that could be done to support >> the >> >> orgs who run multiple cassandra instances on the same node (multiple >> >> gossipers in that case is at least a little wasteful). >> >> >> >> I've also played around with using domain sockets for IPC inside of >> >> cassandra. I never ran a proper benchmark, but there were some >> throughput >> >> advantages to this approach. >> >> >> >> Cheers, >> >> >> >> Gary. >> >> >> >> >> >> On Thu, Feb 22, 2018 at 8:39 PM, Carl Mueller < >> carl.muel...@smartthings.com> >> >> wrote: >> >> >> >>> GC pauses may have been improved in newer releases, since we are in >> 2.1.x, >> >>> but I was wondering why cassandra uses one jvm for all tables and >> >>> keyspaces, intermingling the heap for on-JVM objects. >> >>> >> >>> ... so why doesn't cassandra spin off a jvm per table so each jvm can >> be >> >>> tuned per table and gc tuned and gc impacts not impact other tables? >> It >> >>> would probably increase the number of endpoints if we avoid having an >> >>> overarching query router. >> >>> >> > >> > --------------------------------------------------------------------- >> > To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org >> > For additional commands, e-mail: dev-h...@cassandra.apache.org >> > >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org >> For additional commands, e-mail: dev-h...@cassandra.apache.org >> >> >
