Messages in this thread | | | Date | Sun, 22 May 2011 03:21:26 +0100 | From | Al Viro <> | Subject | Re: [PATCH] VFS: Add VFS event counter infrastructure |
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On Fri, May 13, 2011 at 05:14:12PM -0700, Andi Kleen wrote: > From: Andi Kleen <ak@linux.intel.com> > > The recently discovered problem with RCU walks not working for absolute path > motivated me to add some counters for these events to the VFS. Networking > and VM has had such counters for a long time and they were always useful > to diagnose performance problems. An advantage of counters over tracepoints > is that they are always collected and are low enough overhead that > they can be always enabled (unlike tracing) > > This patch implements a simple per CPU counter framework for the VFS. > The counters are per CPU and are very little overhead. The counters > are output in debugfs (/sys/kernel/fs/vfsstat)
WTF? Since when had debugfs become mandatory?
> + fs = debugfs_create_dir("fs", NULL); > + if (fs) > + debugfs_create_file("vfsstat", 0444, fs, NULL, &vfsstat_fops); > + return 0;
Note that if that FPOS is configured away debugfs_create_dir() does _NOT_ return NULL - you get ERR_PTR(-ENODEV).
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