It's true that a 16GB heap is generally not a good idea; however, it's not clear from the data provided what problem you're trying to solve.
What is it that you don't like about the default settings? -Bryan On Fri, May 3, 2013 at 4:27 AM, Oleg Dulin <oleg.du...@gmail.com> wrote: > Here is my question. It can't possibly be a good set up to use 16gig heap > space, but this is the best I can do. Setting it to default never worked > well for me, setting it to 8g doesn't work well either. It can't keep up > with flushing memtables. It is possibly that someone at some point may have > broken something in the config files. If I were to look for hints there, > what should I look at ? > > Look at my gc log from Cassandra: > > Starts off like this: > > 2013-04-29T08:53:44.548-0400: 5.386: [GC 1677824K->11345K(16567552K), > 0.0509880 secs] > 2 2013-04-29T08:53:47.701-0400: 8.539: [GC 1689169K->42027K(16567552K), > 0.1269180 secs] > 3 2013-04-29T08:54:05.361-0400: 26.199: [GC > 1719851K->231763K(16567552K), 0.1436070 secs] > 4 2013-04-29T08:55:44.797-0400: 125.635: [GC > 1909587K->1480096K(16567552K), 1.2626270 secs] > 5 2013-04-29T08:58:44.367-0400: 305.205: [GC > 3157920K->2358588K(16567552K), 1.1198150 secs] > 6 2013-04-29T09:01:12.167-0400: 453.005: [GC > 4036412K->3634298K(16567552K), 1.0098650 secs] > 7 2013-04-29T09:03:35.204-0400: 596.042: [GC > 5312122K->4339703K(16567552K), 0.4597180 secs] > 8 2013-04-29T09:04:51.562-0400: 672.400: [GC > 6017527K->4956381K(16567552K), 0.5361800 secs] > 9 2013-04-29T09:04:59.205-0400: 680.043: [GC > 6634205K->5131825K(16567552K), 0.1741690 secs] > 10 2013-04-29T09:05:06.638-0400: 687.476: [GC > 6809649K->5027933K(16567552K), 0.0607470 secs] > 11 2013-04-29T09:05:13.908-0400: 694.747: [GC > 6705757K->5012439K(16567552K), 0.0624410 secs] > 12 2013-04-29T09:05:20.909-0400: 701.747: [GC > 6690263K->5039538K(16567552K), 0.0618750 secs] > 13 2013-04-29T09:06:35.914-0400: 776.752: [GC > 6717362K->5819204K(16567552K), 0.5738550 secs] > 14 2013-04-29T09:08:05.589-0400: 866.428: [GC > 7497028K->6678597K(16567552K), 0.6781900 secs] > 15 2013-04-29T09:08:12.458-0400: 873.296: [GC > 8356421K->6865736K(16567552K), 0.1423040 secs] > 16 2013-04-29T09:08:18.690-0400: 879.529: [GC > 8543560K->6742902K(16567552K), 0.0516470 secs] > 17 2013-04-29T09:08:24.914-0400: 885.752: [GC > 8420726K->6725877K(16567552K), 0.0517290 secs] > 18 2013-04-29T09:08:31.008-0400: 891.846: [GC > 8403701K->6741781K(16567552K), 0.0532540 secs] > 19 2013-04-29T09:08:37.201-0400: 898.039: [GC > 8419605K->6759614K(16567552K), 0.0563290 secs] > 20 2013-04-29T09:08:43.493-0400: 904.331: [GC > 8437438K->6772147K(16567552K), 0.0569580 secs] > 21 2013-04-29T09:08:49.757-0400: 910.595: [GC > 8449971K->6776883K(16567552K), 0.0558070 secs] > 22 2013-04-29T09:08:55.973-0400: 916.812: [GC > 8454707K->6789404K(16567552K), 0.0577230 secs] > > …… > > > look what it is today: > > 41536 2013-05-03T07:17:13.519-0400: 339814.357: [GC > 9178946K->9176740K(16567552K), 0.0265830 secs] > 41537 2013-05-03T07:17:19.556-0400: 339820.394: [GC > 10854564K->9178449K(16567552K)**, 0.0253180 secs] > 41538 2013-05-03T07:17:24.390-0400: 339825.228: [GC > 10856273K->9179073K(16567552K)**, 0.0266450 secs] > 41539 2013-05-03T07:17:30.729-0400: 339831.567: [GC > 10856897K->9178629K(16567552K)**, 0.0261150 secs] > 41540 2013-05-03T07:17:35.584-0400: 339836.422: [GC > 10856453K->9178586K(16567552K)**, 0.0250870 secs] > 41541 2013-05-03T07:17:38.514-0400: 339839.352: [GC > 10856410K->9179314K(16567552K)**, 0.0258120 secs] > 41542 2013-05-03T07:17:43.200-0400: 339844.038: [GC > 10857138K->9180160K(16567552K)**, 0.0250150 secs] > 41543 2013-05-03T07:17:46.566-0400: 339847.404: [GC > 10857984K->9179071K(16567552K)**, 0.0264420 secs] > 41544 2013-05-03T07:17:52.913-0400: 339853.751: [GC > 10856895K->9179870K(16567552K)**, 0.0262430 secs] > 41545 2013-05-03T07:17:58.303-0400: 339859.141: [GC > 10857694K->9179209K(16567552K)**, 0.0255130 secs] > 41546 2013-05-03T07:18:03.427-0400: 339864.265: [GC > 10857033K->9178316K(16567552K)**, 0.0263140 secs] > 41547 2013-05-03T07:18:11.657-0400: 339872.495: [GC > 10856140K->9178351K(16567552K)**, 0.0265340 secs] > 41548 2013-05-03T07:18:17.429-0400: 339878.267: [GC > 10856175K->9179067K(16567552K)**, 0.0254820 secs] > 41549 2013-05-03T07:18:21.251-0400: 339882.089: [GC > 10856891K->9179680K(16567552K)**, 0.0264210 secs] > 41550 2013-05-03T07:18:25.062-0400: 339885.900: [GC > 10857504K->9178985K(16567552K)**, 0.0267200 secs] > > > > > -- > Regards, > Oleg Dulin > NYC Java Big Data Engineer > http://www.olegdulin.com/ > > >
