linux-kernel - Re: [patch 10/10] Scheduler profiling

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]

Date:	Sat, 7 Jul 2007 13:55:03 -0400
From:	"Frank Ch. Eigler" <fche@...hat.com>
To:	Adrian Bunk <bunk@...sta.de>
Cc:	Dave Jones <davej@...hat.com>, Chuck Ebbert <cebbert@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Alexey Dobriyan <adobriyan@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 10/10] Scheduler profiling - Use immediate values

Hi, Adrian -

On Sat, Jul 07, 2007 at 07:01:57PM +0200, Adrian Bunk wrote:
> [...]
> > Things are not so simple.  One might not know that one has a
> > performance problem until one tries some analysis tools.  Rebooting
> > into different kernels just to investigate does not work generally [...]
> 
> I'm not getting this:
>
> You'll only start looking into an analysis tool if you have a
> performance problem, IOW if you are not satisfied with the
> performance.

There may be people whose jobs entail continually suspecting
performance problems.  Or one may run instrumentation code on a
long-term basis specifically to locate performance spikes.

> And the debug code will not have been tested on this machine no matter 
> whether it's enabled through a compile option or at runtime.

There is a big difference in favour of the former.  The additional
instrumentation code may be small enough to inspect carefully.  The
rest of the kernel would be unaffected.

> [...]  If you might be able to get a big part of tracing and other
> debug code enabled with a performance penalty of a few percent of
> _kernel_ performance, then you might get much debugging aid without
> any effective impact on application performance.

Agreed.


- FChE
-
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/