[Ocfs2-devel] [PATCH 00/34] OCFS2: Add trace event and replace mlog(0).

[Joel Becker <Joel.Becker@oracle.com>]

On Tue, Jan 04, 2011 at 05:06:53PM +0800, Tao Ma wrote:
> On 01/01/2011 06:39 AM, Joel Becker wrote:
> >On Fri, Dec 31, 2010 at 11:11:31PM +0800, Tao Ma wrote:
> >>On 12/31/2010 08:52 PM, Joel Becker wrote:
> >>>	Overall this seems pretty straightforward.  There wasn't a lot
> >>>of editing of masklog entries; we still have a million tracepoints.  I
> >>>wonder how much memory that will use.  Have you checked the space usage
> >>>of all the sysfs files for all of our tracepoints?
> >>Sorry, I don't know how to check the space usage of these files. any tips?
> >
> >	Just count the number of files and directories added to sysfs.
> >I believe the files disappear when not open, but the directories
> >I think have inode and dentry structures around permanently..
> OK, so
> #find /sys/kernel/debug/tracing/events/ocfs2 -type d|wc -l
> give me 319. Every trace event dir has 4
> members(enable,filter,format and id). So it contains about
> 1600(dir+files).

	I think what matters to count is dirs, because files disappear
when you're not using them.
	If you have 319 trace event directories, that's 319 inodes.  On
my x86, a vanilla struct inode is 360 bytes and a dentry is 136 bytes.
That's 154K always in RAM for these knobs.  I gotta say that I'm not too
worried about 154K.  On x86_64 (ca-build24) this grows to 241K.  I
imagine it will double when cluster and dlm are moved to similar trace
events.
	Are we OK with 300K on x86 and 500K on x86_64 always used up by
these tracing entries?

Joel

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Joel Becker
Senior Development Manager
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127