linux-kernel - Re: [PATCH] new irq tracer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20090218213545.GB3112@redhat.com>
Date:	Wed, 18 Feb 2009 16:35:45 -0500
From:	Jason Baron <jbaron@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...e.hu, rostedt@...dmis.org, linux-kernel@...r.kernel.org,
	acme@...stprotocols.net, fweisbec@...il.com, fche@...hat.com,
	compudj@...stal.dyndns.org
Subject: Re: [PATCH] new irq tracer

On Wed, Feb 18, 2009 at 10:15:25PM +0100, Peter Zijlstra wrote:
> On Wed, 2009-02-18 at 14:53 -0500, Jason Baron wrote:
> > hi,
> > 
> > Using a copule of tracepoints i've implemented an 'irq tracer' which has
> > the following column format:
> > 
> > [time][irq][action][handled][cpu][length]
> > 
> > for example on my system:
> > 
> > [ 1038.927248381]     28     eth0      1        3     0.000002745
> > [ 1038.927544688]     28     eth0      1        3     0.000002520
> > [ 1038.927593609]     28     eth0      1        3     0.000002509
> > [ 1038.974087675]     29     ahci      1        1     0.000013135
> > [ 1038.974288475]     29     ahci      1        1     0.000005542
> > [ 1038.974414324]     29     ahci      1        1     0.000007953
> > 
> > I think this patch is useful in understanding irq system behavior, and
> > for tracking down irq driver handlers that are firing too often or
> > spending too much time handling an irq. This approach could be extended
> > to the timer irq and for softirqs...
> 
> The function graph tracer can already do this, it has a special section
> to recognize irq entry function, and already measures time spend.
> 
> I guess with Steve's new triggers (probes or whatever they ended up
> being called) you could limit it to just IRQ entry points.
> 

i did look at the graph tracer first. While it does measure irq related
functions, it does not give this level of detail concerning which irq #,
which irq handler is involved, and whether or not the irq was handled
successfully or not. So I believe this tracepoints add a level of detail
that the graph tracer does not have. Furthermore, this patch requires 2
tracepoints, not instrumentation for all kernel functions.

thanks,

-Jason



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/