From: "H. Peter Anvin" <hpa@zytor.com>
To: Rodolfo Giometti <giometti@linux.it>
Cc: linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
David Woodhouse <dwmw2@infradead.org>,
Dave Jones <davej@redhat.com>, Sam Ravnborg <sam@ravnborg.org>,
Greg KH <greg@kroah.com>, Randy Dunlap <randy.dunlap@oracle.com>,
Kay Sievers <kay.sievers@vrfy.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>, Ingo Molnar <mingo@elte.hu>,
Michael Kerrisk <mtk.manpages@gmail.com>,
Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 09/11] pps: low level IRQ timestamps recording.
Date: Wed, 02 Dec 2009 16:10:44 -0800 [thread overview]
Message-ID: <4B170204.4080604@zytor.com> (raw)
In-Reply-To: <1259774329-29663-10-git-send-email-giometti@linux.it>
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...
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2009-12-03 0:19 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-02 17:18 LinuxPPS new functionalities Rodolfo Giometti
2009-12-02 17:18 ` [PATCH 01/11] pps: userland header file for PPS API Rodolfo Giometti
2009-12-02 17:18 ` [PATCH 02/11] pps: documentation programs and examples Rodolfo Giometti
2009-12-02 17:18 ` [PATCH 03/11] pps: LinuxPPS clients support Rodolfo Giometti
2009-12-02 17:18 ` [PATCH 04/11] ldisc: new dcd_change() method for line disciplines Rodolfo Giometti
2009-12-02 17:18 ` [PATCH 05/11] ldisc n_tty: export all N_TTY ldisc methods Rodolfo Giometti
2009-12-02 17:18 ` [PATCH 06/11] pps: serial clients support Rodolfo Giometti
2009-12-02 17:18 ` [PATCH 07/11] serial 8250: enable PPS support Rodolfo Giometti
2009-12-02 17:18 ` [PATCH 08/11] pps: parallel port clients support Rodolfo Giometti
2009-12-02 17:18 ` [PATCH 09/11] pps: low level IRQ timestamps recording Rodolfo Giometti
2009-12-02 17:18 ` [PATCH 10/11] serial amba-pl010: enable PPS support Rodolfo Giometti
2009-12-02 17:18 ` [PATCH 11/11] arm: add low level IRQ timestamps recording for arm platforms Rodolfo Giometti
2009-12-03 0:10 ` H. Peter Anvin [this message]
2009-12-03 12:01 ` [PATCH 09/11] pps: low level IRQ timestamps recording Rodolfo Giometti
2009-12-05 6:46 ` H. Peter Anvin
2009-12-02 18:59 ` [PATCH 06/11] pps: serial clients support Alan Cox
2009-12-03 10:53 ` Rodolfo Giometti
2009-12-03 11:46 ` Alan Cox
2009-12-03 12:05 ` Rodolfo Giometti
2009-12-03 12:24 ` Alan Cox
2009-12-02 18:18 ` [PATCH 05/11] ldisc n_tty: export all N_TTY ldisc methods Greg KH
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