linux-kernel - Re: backing up ext4 fs, system unresponsive, thrashing like crazy even though swap is unused

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Message-ID: <CACLa4psEfdA17mcjVHhUfgmARXTZ6AVA7QJ77DymXBeVtgjZ5w@mail.gmail.com>
Date:	Mon, 3 Dec 2012 13:47:15 -0500
From:	Eric Paris <eparis@...isplace.org>
To:	"Theodore Ts'o" <tytso@....edu>,
	Dimitrios Apostolou <jimis@....net>,
	Roland Eggner <edvx1@...temanalysen.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Catalin Marinas <catalin.marinas@....com>
Subject: Re: backing up ext4 fs, system unresponsive, thrashing like crazy
 even though swap is unused

On Mon, Dec 3, 2012 at 12:43 PM, Theodore Ts'o <tytso@....edu> wrote:

> If you are seeing a large number of inodes still in the ext4 inode
> cache after using drop_caches, then I'd look to see whether you have
> something like SELinux or auditing enabled which is pinning a bunch of
> dentries or inodes

You can safely ignore this suggestion as it does make sense.  SELinux
only grabs a references to dentries during its call to
fs_ops->getxattr, which can't last a meaningful length of time (unless
the filesystem is busted).  It only grabs references to inodes during
system initialization, when you couldn't have many in core.

Audit, likewise, only grabs a reference to a dentry during execve()
and only long enough to run getxattr and does not grab any reference
directly to an inode at all.

> or whether your backup program (or some other
> program running on your system) is keeping lots of directories or
> inodes open for some reason.

Certainly could be this suggestion though..
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