In that case I would assume the problem is that for some reason JAMM is failing to load, and so the liveRatio it would ordinarily calculate is defaulting to 10 - are you using the bundled cassandra launch scripts?
On 4 June 2014 15:51, Idrén, Johan <johan.id...@dice.se> wrote: > I wasn’t supplying it, I was assuming it was using the default. It does > not exist in my config file. Sorry for the confusion. > > > > From: Benedict Elliott Smith <belliottsm...@datastax.com> > Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org> > Date: Wednesday 4 June 2014 16:36 > To: "user@cassandra.apache.org" <user@cassandra.apache.org> > > Subject: Re: memtable mem usage off by 10? > > Oh, well ok that explains why I'm not seeing a flush at 750MB. Sorry, >> I was going by the documentation. It claims that the property is around in >> 2.0. > > But something else is wrong, as Cassandra will crash if you supply an > invalid property, implying it's not sourcing the config file you're using. > I'm afraid I don't have the context for why it was removed, but it > happened as part of the 2.0 release. > >> > > On 4 June 2014 13:59, Jack Krupansky <j...@basetechnology.com> wrote: > >> Yeah, it is in the doc: >> >> http://www.datastax.com/documentation/cassandra/2.0/cassandra/configuration/configCassandra_yaml_r.html >> >> And I don’t find a Jira issue mentioning it being removed, so... what’s >> the full story there?! >> >> -- Jack Krupansky >> >> *From:* Idrén, Johan <johan.id...@dice.se> >> *Sent:* Wednesday, June 4, 2014 8:26 AM >> *To:* user@cassandra.apache.org >> *Subject:* RE: memtable mem usage off by 10? >> >> >> Oh, well ok that explains why I'm not seeing a flush at 750MB. Sorry, I >> was going by the documentation. It claims that the property is around in >> 2.0. >> >> >> >> If we skip that, part of my reply still makes sense: >> >> >> >> Having memtable_total_size_in_mb set to 20480, memtables are flushed at a >> reported value of ~2GB. >> >> >> >> With a constant overhead of ~10x, as suggested, this would mean that it >> used 20GB, which is 2x the size of the heap. >> >> >> >> That shouldn't work. According to the OS, cassandra doesn't use more than >> ~11-12GB. >> >> >> ------------------------------ >> *From:* Benedict Elliott Smith <belliottsm...@datastax.com> >> *Sent:* Wednesday, June 4, 2014 2:07 PM >> *To:* user@cassandra.apache.org >> *Subject:* Re: memtable mem usage off by 10? >> >> I'm confused: there is no flush_largest_memtables_at property in C* 2.0? >> >> >> On 4 June 2014 12:55, Idrén, Johan <johan.id...@dice.se> wrote: >> >>> Ok, so the overhead is a constant modifier, right. >>> >>> >>> >>> The 3x I arrived at with the following assumptions: >>> >>> >>> >>> heap is 10GB >>> >>> Default memory for memtable usage is 1/4 of heap in c* 2.0 >>> max memory used for memtables is 2,5GB (10/4) >>> >>> flush_largest_memtables_at is 0.75 >>> >>> flush largest memtables when memtables use 7,5GB (3/4 of heap, 3x of the >>> default) >>> >>> >>> >>> With an overhead of 10x, it makes sense that my memtable is flushed when >>> the jmx data says it is at ~250MB, ie 2,5GB, ie 1/4 of the heap >>> >>> >>> >>> After I've set the memtable_total_size_in_mb to a value larger than >>> 7,5GB, it should still not go over 7,5GB on account of >>> flush_largest_memtables_at, 3/4 the heap >>> >>> >>> >>> So I would expect to see memtables flushed to disk after they're being >>> reportedly at around 750MB. >>> >>> >>> >>> Having memtable_total_size_in_mb set to 20480, memtables are flushed at >>> a reported value of ~2GB. >>> >>> >>> >>> With a constant overhead, this would mean that it used 20GB, which is 2x >>> the size of the heap, instead of 3/4 of the heap as it should be if >>> flush_largest_memtables_at was being respected. >>> >>> >>> >>> This shouldn't be possible. >>> >>> >>> ------------------------------ >>> *From:* Benedict Elliott Smith <belliottsm...@datastax.com> >>> *Sent:* Wednesday, June 4, 2014 1:19 PM >>> >>> *To:* user@cassandra.apache.org >>> *Subject:* Re: memtable mem usage off by 10? >>> >>> Unfortunately it looks like the heap utilisation of memtables was not >>> exposed in earlier versions, because they only maintained an estimate. >>> >>> The overhead scales linearly with the amount of data in your memtables >>> (assuming the size of each cell is approx. constant). >>> >>> flush_largest_memtables_at is an independent setting to >>> memtable_total_space_in_mb, and generally has little effect. Ordinarily >>> sstable flushes are triggered by hitting the memtable_total_space_in_mb >>> limit. I'm afraid I don't follow where your 3x comes from? >>> >>> >>> On 4 June 2014 12:04, Idrén, Johan <johan.id...@dice.se> wrote: >>> >>>> Aha, ok. Thanks. >>>> >>>> >>>> >>>> Trying to understand what my cluster is doing: >>>> >>>> >>>> >>>> cassandra.db.memtable_data_size only gets me the actual data but not >>>> the memtable heap memory usage. Is there a way to check for heap memory >>>> usage? >>>> >>>> >>>> I would expect to hit the flush_largest_memtables_at value, and this >>>> would be what causes the memtable flush to sstable then? By default 0.75? >>>> >>>> >>>> Then I would expect the amount of memory to be used to be maximum ~3x >>>> of what I was seeing when I hadn't set memtable_total_space_in_mb (1/4 by >>>> default, max 3/4 before a flush), instead of close to 10x (250mb vs 2gb). >>>> >>>> >>>> This is of course assuming that the overhead scales linearly with the >>>> amount of data in my table, we're using one table with three cells in this >>>> case. If it hardly increases at all, then I'll give up I guess :) >>>> >>>> At least until 2.1.0 comes out and I can compare. >>>> >>>> >>>> BR >>>> >>>> Johan >>>> >>>> >>>> ------------------------------ >>>> *From:* Benedict Elliott Smith <belliottsm...@datastax.com> >>>> *Sent:* Wednesday, June 4, 2014 12:33 PM >>>> >>>> *To:* user@cassandra.apache.org >>>> *Subject:* Re: memtable mem usage off by 10? >>>> >>>> These measurements tell you the amount of user data stored in the >>>> memtables, not the amount of heap used to store it, so the same applies. >>>> >>>> >>>> On 4 June 2014 11:04, Idrén, Johan <johan.id...@dice.se> wrote: >>>> >>>>> I'm not measuring memtable size by looking at the sstables on disk, >>>>> no. I'm looking through the JMX data. So I would believe (or hope) that >>>>> I'm >>>>> getting relevant data. >>>>> >>>>> >>>>> >>>>> If I have a heap of 10GB and set the memtable usage to 20GB, I would >>>>> expect to hit other problems, but I'm not seeing memory usage over 10GB >>>>> for >>>>> the heap, and the machine (which has ~30gb of memory) is showing ~10GB >>>>> free, with ~12GB used by cassandra, the rest in caches. >>>>> >>>>> >>>>> >>>>> Reading 8k rows/s, writing 2k rows/s on a 3 node cluster. So it's not >>>>> idling. >>>>> >>>>> >>>>> >>>>> BR >>>>> >>>>> Johan >>>>> >>>>> >>>>> ------------------------------ >>>>> *From:* Benedict Elliott Smith <belliottsm...@datastax.com> >>>>> *Sent:* Wednesday, June 4, 2014 11:56 AM >>>>> *To:* user@cassandra.apache.org >>>>> *Subject:* Re: memtable mem usage off by 10? >>>>> >>>>> If you are storing small values in your columns, the object >>>>> overhead is very substantial. So what is 400Mb on disk may well be 4Gb in >>>>> memtables, so if you are measuring the memtable size by the resulting >>>>> sstable size, you are not getting an accurate picture. This overhead has >>>>> been reduced by about 90% in the upcoming 2.1 release, through tickets >>>>> 6271 <https://issues.apache.org/jira/browse/CASSANDRA-6271>, 6689 >>>>> <https://issues.apache.org/jira/browse/CASSANDRA-6689> and 6694 >>>>> <https://issues.apache.org/jira/browse/CASSANDRA-6694>. >>>>> >>>>> >>>>> On 4 June 2014 10:49, Idrén, Johan <johan.id...@dice.se> wrote: >>>>> >>>>>> Hi, >>>>>> >>>>>> >>>>>> >>>>>> I'm seeing some strange behavior of the memtables, both in 1.2.13 and >>>>>> 2.0.7, basically it looks like it's using 10x less memory than it should >>>>>> based on the documentation and options. >>>>>> >>>>>> >>>>>> >>>>>> 10GB heap for both clusters. >>>>>> >>>>>> 1.2.x should use 1/3 of the heap for memtables, but it uses max >>>>>> ~300mb before flushing >>>>>> >>>>>> >>>>>> >>>>>> 2.0.7, same but 1/4 and ~250mb >>>>>> >>>>>> >>>>>> >>>>>> In the 2.0.7 cluster I set the memtable_total_space_in_mb to 4096, >>>>>> which then allowed cassandra to use up to ~400mb for memtables... >>>>>> >>>>>> >>>>>> >>>>>> I'm now running with 20480 for memtable_total_space_in_mb and >>>>>> cassandra is using ~2GB for memtables. >>>>>> >>>>>> >>>>>> >>>>>> Soo, off by 10 somewhere? Has anyone else seen this? Can't find a >>>>>> JIRA for any bug connected to this. >>>>>> >>>>>> java 1.7.0_55, JNA 4.1.0 (for the 2.0 cluster) >>>>>> >>>>>> >>>>>> >>>>>> BR >>>>>> >>>>>> Johan >>>>>> >>>>> >>>>> >>>> >>>> >>> >>> >> >> > >
