From: Masami Hiramatsu <mhiramat@redhat.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Theodore Tso <tytso@mit.edu>,
"Frank Ch. Eigler" <fche@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
systemtap@sourceware.org,
Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Subject: Re: [PATCH] simple dprobe like markers for the kernel
Date: Mon, 14 Jul 2008 16:28:00 -0000 [thread overview]
Message-ID: <487B7E37.9050600@redhat.com> (raw)
In-Reply-To: <1215886965.3360.16.camel@localhost.localdomain>
Hi James,
James Bottomley wrote:
> This is just an incremental update based on feedback. The most
> significant was that making the marker a compiler barrier will free the
> inserter from worrying about the mark sliding around changes to named
> variables (and thus having to worry about this in placement) at
> practically zero optimisation cost. I also updated the code to drop and
> asm section instead of using the static variable scheme. I also added
> documentation and made the module loader ignore them (since modules
> don't go through the vmlinux.lds transformations).
I'm very interested in your approach.
IMHO, as Aoki investigated, the overhead of markers is not so big
unless we put a lot of them into kernel. And from "active"
overhead point of view, it takes less than tens of nano-seconds,
while kprobes takes hundreds of nano-seconds. Kprobe also has a
limitation of probable points, it can't probe "__kprobes" marked
functions. So, original markers still has advantages.
However, your approach is also useful, especially for embedding
thousands of markers in kernel or drivers.
So I think it's better to use both of them as the situation demands.
I just have one comment on its name. Since it doesn't trace
anything, so I'd rather like notation() or note_mark() than
trace_simple(). :-)
Thank you,
>
> I also added a simple versioning scheme (basically tack the version on
> to the end of the section name). It can be used simply and even
> provides backwards compatibility (just emit the old and the new
> sections).
>
> If everyone's happy with this, I'll follow it up with the systemtap
> changes to make use of them ... they've been incredibly helpful
> debugging some of the CDROM problems for me so far.
>
> James
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division
e-mail: mhiramat@redhat.com
next prev parent reply other threads:[~2008-07-14 16:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1215638551.3444.39.camel__22002.9595810503$1215638656$gmane$org@localhost.localdomain>
2008-07-10 2:30 ` [RFC] " Frank Ch. Eigler
2008-07-10 13:51 ` James Bottomley
2008-07-10 14:23 ` Frank Ch. Eigler
2008-07-10 14:46 ` James Bottomley
2008-07-10 15:30 ` Theodore Tso
2008-07-10 15:57 ` James Bottomley
2008-07-10 18:20 ` Frank Ch. Eigler
2008-07-12 18:23 ` [PATCH] " James Bottomley
2008-07-12 20:05 ` [PATCH] systemtap: add parser for simple markers James Bottomley
2008-07-12 23:08 ` Frank Ch. Eigler
2008-07-14 16:28 ` Masami Hiramatsu [this message]
2008-07-14 22:03 ` [PATCH] simple dprobe like markers for the kernel James Bottomley
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=487B7E37.9050600@redhat.com \
--to=mhiramat@redhat.com \
--cc=James.Bottomley@HansenPartnership.com \
--cc=fche@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@polymtl.ca \
--cc=systemtap@sourceware.org \
--cc=tytso@mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).