[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20091203120130.GD12943@gundam.enneenne.com>
Date: Thu, 3 Dec 2009 13:01:30 +0100
From: Rodolfo Giometti <giometti@...eenne.com>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
David Woodhouse <dwmw2@...radead.org>,
Dave Jones <davej@...hat.com>, Sam Ravnborg <sam@...nborg.org>,
Greg KH <greg@...ah.com>,
Randy Dunlap <randy.dunlap@...cle.com>,
Kay Sievers <kay.sievers@...y.org>,
Alan Cox <alan@...rguk.ukuu.org.uk>,
Ingo Molnar <mingo@...e.hu>,
Michael Kerrisk <mtk.manpages@...il.com>,
Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 09/11] pps: low level IRQ timestamps recording.
On Wed, Dec 02, 2009 at 04:10:44PM -0800, H. Peter Anvin wrote:
> On 12/02/2009 09:18 AM, Rodolfo Giometti wrote:
> > Add low level IRQ timestamps recording for x86 (32 and 64 bits)
> > platforms and enable UART clients in order to use it.
> >
> > This improves PPS precision. :)
>
> It also invokes getnstimeofday on every single interrupt, including ones
> which have absolutely nothing to do with the PPS, and are potentially
> high volume. getnstimeofday can be a fairly expensive operation,
> especially if the best available clock is away from the CPU, or it
> requires extensive arithmetic in order to normalize the clock value...
I see, that's why I propose my patches to you: in order to have some
feedbacks for better solutions. :)
Can I add a IRQF_TIMESTAMP in order to ask to the system to record irq
timestamps for particular irq lines? The problem is that I cannot set
that flag at irq_register() time but I have to do it later... it can
be a problem?
Ciao,
Rodolfo
--
GNU/Linux Solutions e-mail: giometti@...eenne.com
Linux Device Driver giometti@...ux.it
Embedded Systems phone: +39 349 2432127
UNIX programming skype: rodolfo.giometti
Freelance ICT Italia - Consulente ICT Italia - www.consulenti-ict.it
--
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/
Powered by blists - more mailing lists