cassandra节点由于oom而宕机，检查下面的/var/log/消息。

Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: java invoked oom-killer: gfp_mask=0x280da, order=0, oom_score_adj=0
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: java cpuset=/ mems_allowed=0
....
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: Node 0 DMA: 1*4kB (U) 0*8kB 0*16kB 1*32kB (U) 2*64kB (U) 1*128kB (U) 1*256kB (U) 0*512kB 1*1024kB (U) 1*2048kB (M) 3*4096kB (M) = 15908kB
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: Node 0 DMA32: 1294*4kB (UM) 932*8kB (UEM) 897*16kB (UEM) 483*32kB (UEM) 224*64kB (UEM) 114*128kB (UEM) 41*256kB (UEM) 12*512kB (UEM) 7*1024kB (UE
M) 2*2048kB (EM) 35*4096kB (UM) = 242632kB
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: Node 0 Normal: 5319*4kB (UE) 3233*8kB (UEM) 960*16kB (UE) 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 62500kB
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=1048576kB
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: 38109 total pagecache pages
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: 0 pages in swap cache
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: Swap cache stats: add 0, delete 0, find 0/0
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: Free swap  = 0kB
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: Total swap = 0kB
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: 16394647 pages RAM
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: 0 pages HighMem/MovableOnly
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: 310559 pages reserved
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [ pid ]   uid  tgid total_vm      rss nr_ptes swapents oom_score_adj name
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [ 2634]     0  2634    41614      326      82        0             0 systemd-journal
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [ 2690]     0  2690    29793      541      27        0             0 lvmetad
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [ 2710]     0  2710    11892      762      25        0         -1000 systemd-udevd
.....
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [13774]     0 13774   459778    97729     429        0             0 Scan Factory
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [14506]     0 14506    21628     5340      24        0             0 macompatsvc
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [14586]     0 14586    21628     5340      24        0             0 macompatsvc
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [14588]     0 14588    21628     5340      24        0             0 macompatsvc
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [14589]     0 14589    21628     5340      24        0             0 macompatsvc
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [14598]     0 14598    21628     5340      24        0             0 macompatsvc
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [14599]     0 14599    21628     5340      24        0             0 macompatsvc
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [14600]     0 14600    21628     5340      24        0             0 macompatsvc
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [14601]     0 14601    21628     5340      24        0             0 macompatsvc
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [19679]     0 19679    21628     5340      24        0             0 macompatsvc
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [19680]     0 19680    21628     5340      24        0             0 macompatsvc
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [ 9084]  1007  9084  2822449   260291     810        0             0 java
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [ 8509]  1007  8509 17223585 14908485   32510        0             0 java
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [21877]     0 21877   461828    97716     318        0             0 ScanAction Mgr
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [21884]     0 21884   496653    98605     340        0             0 OAS Manager
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [31718]    89 31718    25474      486      48        0             0 pickup
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [ 4891]  1007  4891    26999      191       9        0             0 iostat
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: [ 4957]  1007  4957    26999      192      10        0             0 iostat
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: Out of memory: Kill process 8509 (java) score 928 or sacrifice child
Jan 23 20:07:17 ip-xxx-xxx-xxx-xxx kernel: Killed process 8509 (java) total-vm:68894340kB, anon-rss:59496344kB, file-rss:137596kB, shmem-rss:0kB

除了带有搜索和监视代理的dse cassandra之外，此主机上没有其他运行程序。最大堆大小设置为31g，cassandrajava进程在出错时似乎使用了~57gb（ram为62gb）。所以我猜jvm开始使用大量内存并触发oom错误。我的理解正确吗？这是linux触发的jvm杀死，因为jvm消耗的内存超过了可用内存？
所以在本例中，jvm使用的最大值是31g，剩余的26gb是非堆内存。通常，这个进程需要42g左右的时间，而且在oom的时候它消耗了57g，我怀疑java进程是罪魁祸首而不是受害者。
在问题出现时，没有进行堆转储，我现在已经对其进行了配置。但即使采取堆转储，也有助于找出谁消耗了更多内存。heapdump只转储堆内存区，应该用什么来转储非heapdump？本机内存跟踪是我遇到的一件事。有什么方法可以在oom发生时转储本机内存吗？监视jvm内存以诊断oom错误的最佳方法是什么？