[Bug 1047566] Re: Memory leaks when using NFS

[Brian Norris]

I think Andrew is referring to my team in comment #7 (my NFS exports are
on an ext3 partition). I can confirm that mainline kernel 3.2.27-generic
does *not* resolve the leak, as I recently noticed the leak again. I
think it was a NFSv3 vs. v4 issue, as many of my clients moved back to
v3 as an attempt to resolve the issue. But a few rarely-utilized clients
remained, and it seems that NFSv4 activity from these clients correlates
with memory leakage in idr_layer_cache.

So, I've seen the leak on all the following:

3.2.0-30-generic
3.2.0-29-generic
3.2.27-030227-generic

The last kernel is a vanilla build from the Ubuntu PPA:
http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.2.27-precise/

So, I think that this is an upstream leak, at least in the 3.2.x stable
branch.

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https://bugs.launchpad.net/bugs/1047566

Title:
  Memory leaks when using NFS

Status in “nfs-utils” package in Ubuntu:
  Confirmed

Bug description:
  When using Ubuntu Server 12.04 with or without the latest updates
  (kernels 3.2.0-23 and 3.2.0-29, x86_64) as an NFS server with fairly
  heavy reading activity from clients (no writing), from a volume with a
  lot of small files, split into many subdirectories (with about 5-10
  files or subdirectories per directory, in a tree-like structure not
  unlike that of Squid proxy), available memory is quickly exhausted,
  however no single process shows that much memory being used, nor does
  the "buffers" or "cached" in "free" command output. The server
  eventually runs out of memory and crashes.

  slabtop shows that majority of memory is being used by idr_layer_cache
  (3.6G on a sever with 4G of RAM shortly before the kernel started
  killing processes and eventually crashed).

  The filesystem being shared is ext4. Clients (also the same version of
  Ubuntu Server) mount the volume in read-only mode, with default
  options.

  P.S. Also tried i386 version, with the same result.

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