From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 14972] [regression] msync() call on ext4 causes disk thrashing
Date: Sat, 2 Jan 2010 17:54:55 GMT
Message-ID: <201001021754.o02HstpS022786@demeter.kernel.org>
References: <bug-14972-13602@http.bugzilla.kernel.org/>
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http://bugzilla.kernel.org/show_bug.cgi?id=14972





--- Comment #6 from Theodore Tso <tytso@mit.edu>  2010-01-02 17:54:54 ---
You need to compile kernel with CONFIG_BLK_DEV_IO_TRACE and then you need to
make sure that the debugfs file system is mounted in /sys/kernel/debug, i.e.:

    mount -t debugfs none /sys/kernel/debug

The following documentation is from 2007, so there are some newer features (and
the underlying implementation has moved to using ftrace), but the basic user
interface hasn't changed much:

    http://pdfedit.petricek.net/bt/file_download.php?file_id=17&type=bug

More information:

    http://www.gelato.org/pdf/apr2006/gelato_ICE06apr_blktrace_brunelle_hp.pdf

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