linux-kernel - Re: >10% performance degradation since 2.6.18

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: <20090703191321.GO5480@parisc-linux.org>
Date:	Fri, 3 Jul 2009 13:13:22 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	"Styner, Douglas W" <douglas.w.styner@...el.com>,
	Chinang Ma <chinang.ma@...el.com>,
	"Prickett, Terry O" <terry.o.prickett@...el.com>,
	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	Eric.Moore@....com, DL-MPTFusionLinux@....com
Subject: Re: >10% performance degradation since 2.6.18

On Fri, Jul 03, 2009 at 08:54:14PM +0200, Jens Axboe wrote:
> On Fri, Jul 03 2009, Andi Kleen wrote:
> > 
> > Matthew Wilcox <matthew@....cx> writes:
> > >
> > > ======oprofile CPU_CLK_UNHALTED for top 30 functions
> > > Cycles% 2.6.18-92.el5-op           Cycles% 2.6.30
> > > 70.1409 <database>                 67.0207 <database>
> > > 1.3556 mpt_interrupt               1.7029 mpt_interrupt
> > 
> > It's strange that mpt_interrupt is that more costly in 2.6.30
> > than in 2.6.18. I diffed 2.6.30's drivers/message/fusion/mptbase.c
> > to a rhel 5.3s and they seem to be about the same. 
> > 
> > So why does it cost 0.5% more in 2.6.30?
> > 
> > [adding MPT maintainers]
> 
> Look at the irqs/sec rate, it's higher by about the same percentage. So
> it's likely not a more costly irq handler, it's likely just called that
> much more. It could be IO pattern, causing more commands to be issued
> (which leads to more interrupts, etc).

Yes, but the irqs/sec increase doesn't appear to be due to MPT interrupts.
In the /proc/interrupt summaries, RH5 did 388666895 IOC interrupts and
2.6.30 did 378419042.  As a percentage of interrupts, the IOC interrupts
were 59.4% with RH and 51.8% with 2.6.30.

This isn't quite conclusive since the collection of /proc/interrupts is
over the entire life of the system, not during the measurement period.
But I do find it persuasive.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
--
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/