jm + oom-killer   3

How to stop Ubuntu Xenial (16.04) from randomly killing your big processes
ugh.
Unfortunately, a bug was recently introduced into the allocator which made it sometimes not try hard enough to free kernel cache memory before giving up and invoking the OOM killer. In practice, this means that at random times, the OOM killer would strike at big processes when the kernel tries to allocate, say, 16 kilobytes of memory for a new process’s thread stack — even when there are many gigabytes of memory in reclaimable kernel caches!
oom-killer  ooms  linux  ops  16.04 
7 weeks ago by jm
Transparent huge pages implicated in Redis OOM
A nasty real-world prod error scenario worsened by THPs:
jemalloc(3) extensively uses madvise(2) to notify the operating system that it's done with a range of memory which it had previously malloc'ed. The page size on this machine is 2MB because transparent huge pages are in use. As such, a lot of the memory which is being marked with madvise(..., MADV_DONTNEED) is within substantially smaller ranges than 2MB. This means that the operating system never was able to evict pages which had ranges marked as MADV_DONTNEED because the entire page has to be unneeded to allow a page to be reused. Despite initially looking like a leak, the operating system itself was unable to free memory because of madvise(2) and transparent huge pages. This led to sustained memory pressure on the machine and redis-server eventually getting OOM killed.
oom-killer  oom  linux  ops  thp  jemalloc  huge-pages  madvise  redis  memory 
march 2015 by jm
Taming the OOM killer [LWN.net]
hmm, I never knew about oom_adj, useful (via Peter Blair)
via:petermblair  oom  linux  memory  oom-killer  sysadmin  lwn  from delicious
january 2011 by jm

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