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To: ch huang <justlooks@gmail.com>
Cc: systemtap@sourceware.org
Subject: Re: problem in run systemtap script
References: <CACeqxwQRVHN0_wjMqpmi1WfaF6C6OZazvTscyzRX-8f5ww5VyA@mail.gmail.com>
From: fche@redhat.com (Frank Ch. Eigler)
Date: Tue, 13 Mar 2012 14:20:00 -0000
In-Reply-To: <CACeqxwQRVHN0_wjMqpmi1WfaF6C6OZazvTscyzRX-8f5ww5VyA@mail.gmail.com> (ch huang's message of "Tue, 13 Mar 2012 16:17:23 +0800")
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ch huang <justlooks@gmail.com> writes:

> how to handle this?
> [...]
> WARNING: probe module("ext3").function("ext3_journalled_set_page_dirty@fs/ext3/inode.c:1780").call
> (address 0xffffffff8804dff8) registration error (rc -22)
> WARNING: probe module("ext3").function("bget_one@fs/ext3/inode.c:1419").call
> (address 0xffffffff8804d50a) registration error (rc -22)
> [...]

This could be the kernel kprobes limitation also mentioned in
<https://bugzilla.redhat.com/show_bug.cgi?id=801785>.  Some functions
will simply miss being probed.  But note that they are all warnings.

> ERROR: probe overhead exceeded threshold
> WARNING: Number of errors: 1, skipped probes: 0

This would be the real problem.  Rerun with -DSTP_NO_OVERLOAD to
disable the overload-prevention mechanism.

- FChE