Hi Wade I don't know if your scenario matches mine, but I've been struggling with memory pressure in 1.x as well. I made the jump from 0.7.9 to 1.1.0, along with enabling compression and levelled compactions, so I don't know which specifically is the main culprit.
Specifically, all my nodes seem to "lose" heap memory. As parnew and CMS do their job, over any reasonable period of time, the "floor" of memory after a GC keeps rising. This is quite visible if you leave jconsole connected for a day or so, and manifests itself as a funny-looking cone like so: http://mina.naguib.ca/images/cassandra_jconsole.png Once memory pressure reaches a point where the heap can't be maintained reliably below 75%, cassandra goes into survival mode - via a bunch of tunables in cassandra.conf it'll do things like flush memtables, drop caches, etc - all of which, in my experience, especially with the recent off-heap data structures, exasperate the problem. I've been meaning, of course, to collect enough technical data to file a bug report, but haven't had the time. I have not yet tested 1.1.1 to see if it improves the situation. What I have found however, is a band-aid which you see at the rightmost section of the graph in the screenshot I posted. That is simply to hit "Perform GC" button in jconsole. It seems that a full System.gc() *DOES* reclaim heap memory that parnew and CMS fail to reclaim. On my production cluster I have a full-GC via JMX scheduled in a rolling fashion every 4 hours. It's extremely expensive (20-40 seconds of unresponsiveness) but is a necessary evil in my situation. Without it, my nodes enter a nasty spiral of constant flushing, constant compactions, high heap usage, instability and high latency. On 2012-06-05, at 2:56 PM, Poziombka, Wade L wrote: > Alas, upgrading to 1.1.1 did not solve my issue. > > -----Original Message----- > From: Brandon Williams [mailto:dri...@gmail.com] > Sent: Monday, June 04, 2012 11:24 PM > To: user@cassandra.apache.org > Subject: Re: memory issue on 1.1.0 > > Perhaps the deletes: https://issues.apache.org/jira/browse/CASSANDRA-3741 > > -Brandon > > On Sun, Jun 3, 2012 at 6:12 PM, Poziombka, Wade L > <wade.l.poziom...@intel.com> wrote: >> Running a very write intensive (new column, delete old column etc.) process >> and failing on memory. Log file attached. >> >> Curiously when I add new data I have never seen this have in past sent >> hundreds of millions "new" transactions. It seems to be when I >> modify. my process is as follows >> >> key slice to get columns to modify in batches of 100, in separate threads >> modify those columns. I advance the slice with the start key each with last >> key in previous batch. Mutations done are update a column value in one >> column family(token), delete column and add new column in another (pan). >> >> Runs well until after about 5 million rows then it seems to run out of >> memory. Note that these column families are quite small. >> >> WARN [ScheduledTasks:1] 2012-06-03 17:49:01,558 GCInspector.java (line >> 145) Heap is 0.7967470834946492 full. You may need to reduce memtable >> and/or cache sizes. Cassandra will now flush up to the two largest >> memtables to free up memory. Adjust flush_largest_memtables_at >> threshold in cassandra.yaml if you don't want Cassandra to do this >> automatically >> INFO [ScheduledTasks:1] 2012-06-03 17:49:01,559 StorageService.java >> (line 2772) Unable to reduce heap usage since there are no dirty >> column families >> INFO [GossipStage:1] 2012-06-03 17:49:01,999 Gossiper.java (line 797) >> InetAddress /10.230.34.170 is now UP >> INFO [ScheduledTasks:1] 2012-06-03 17:49:10,048 GCInspector.java >> (line 122) GC for ParNew: 206 ms for 1 collections, 7345969520 used; >> max is 8506048512 >> INFO [ScheduledTasks:1] 2012-06-03 17:49:53,187 GCInspector.java >> (line 122) GC for ConcurrentMarkSweep: 12770 ms for 1 collections, >> 5714800208 used; max is 8506048512 >> >> ---------------- >> Keyspace: keyspace >> Read Count: 50042632 >> Read Latency: 0.23157864418482224 ms. >> Write Count: 44948323 >> Write Latency: 0.019460829472992797 ms. >> Pending Tasks: 0 >> Column Family: pan >> SSTable count: 5 >> Space used (live): 1977467326 >> Space used (total): 1977467326 >> Number of Keys (estimate): 16334848 >> Memtable Columns Count: 0 >> Memtable Data Size: 0 >> Memtable Switch Count: 74 >> Read Count: 14985122 >> Read Latency: 0.408 ms. >> Write Count: 19972441 >> Write Latency: 0.022 ms. >> Pending Tasks: 0 >> Bloom Filter False Postives: 829 >> Bloom Filter False Ratio: 0.00073 >> Bloom Filter Space Used: 37048400 >> Compacted row minimum size: 125 >> Compacted row maximum size: 149 >> Compacted row mean size: 149 >> >> Column Family: token >> SSTable count: 4 >> Space used (live): 1250973873 >> Space used (total): 1250973873 >> Number of Keys (estimate): 14217216 >> Memtable Columns Count: 0 >> Memtable Data Size: 0 >> Memtable Switch Count: 49 >> Read Count: 30059563 >> Read Latency: 0.167 ms. >> Write Count: 14985488 >> Write Latency: 0.014 ms. >> Pending Tasks: 0 >> Bloom Filter False Postives: 13642 >> Bloom Filter False Ratio: 0.00322 >> Bloom Filter Space Used: 28002984 >> Compacted row minimum size: 150 >> Compacted row maximum size: 258 >> Compacted row mean size: 224 >> >> Column Family: counters >> SSTable count: 2 >> Space used (live): 561549994 >> Space used (total): 561549994 >> Number of Keys (estimate): 9985024 >> Memtable Columns Count: 0 >> Memtable Data Size: 0 >> Memtable Switch Count: 38 >> Read Count: 4997947 >> Read Latency: 0.092 ms. >> Write Count: 9990394 >> Write Latency: 0.023 ms. >> Pending Tasks: 0 >> Bloom Filter False Postives: 191 >> Bloom Filter False Ratio: 0.37525 >> Bloom Filter Space Used: 18741152 >> Compacted row minimum size: 125 >> Compacted row maximum size: 179 >> Compacted row mean size: 150 >> >> ----------------
