From: Dave Hansen <dave@sr71.net>
To: Adam Goode <adam@evdebs.org>
Cc: Pavel Machek <pavel@suse.cz>, Jens Axboe <axboe@suse.de>,
Alejandro Bonilla Beeche <abonilla@linuxwireless.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
hdaps devel <hdaps-devel@lists.sourceforge.net>
Subject: Re: [Hdaps-devel] Re: HDAPS, Need to park the head for real
Date: Thu, 18 Aug 2005 14:30:31 -0700 [thread overview]
Message-ID: <1124400632.6546.3.camel@localhost> (raw)
In-Reply-To: <1124399756.28353.0.camel@lynx.auton.cs.cmu.edu>
On Thu, 2005-08-18 at 17:15 -0400, Adam Goode wrote:
> On Thu, 2005-08-18 at 22:49 +0200, Pavel Machek wrote:
> > Please make it "echo 1 > frozen", then userspace can do "echo 0 > frozen"
> > after five seconds.
>
> What if the code to do "echo 0 > frozen" is swapped out to disk? ;)
In the real world, to be really sure that you're not doing a trip out to
the disk, you'll need a daemon which doesn't do any allocations between
when it's notified and when it does the write to the control file.
In reality, that probably means a statically compiled daemon that
mlock()s itself, and any structures that it will need. It _might_ even
need to keep an open file descriptor on the "frozen" file. Because, in
theory, that file could be written out to the sysfs backing store.
-- Dave
next prev parent reply other threads:[~2005-08-18 21:30 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-08-16 15:25 HDAPS, Need to park the head for real Alejandro Bonilla Beeche
2005-08-16 15:34 ` Lee Revell
2005-08-16 15:41 ` Alejandro Bonilla Beeche
2005-08-16 20:07 ` Jens Axboe
2005-08-16 23:15 ` Alejandro Bonilla Beeche
2005-08-16 23:29 ` [Hdaps-devel] " Yani Ioannou
2005-08-17 5:53 ` Jens Axboe
2005-08-17 6:23 ` [Hdaps-devel] " Jon Escombe
2005-08-17 7:47 ` Avi Kivity
2005-08-17 7:56 ` Jens Axboe
2005-08-18 20:49 ` Pavel Machek
2005-08-18 21:15 ` Adam Goode
2005-08-18 21:30 ` Dave Hansen [this message]
2005-08-18 21:38 ` Pavel Machek
2005-08-19 6:36 ` Jens Axboe
2005-08-19 10:05 ` [Hdaps-devel] " Jon Escombe
2005-08-19 10:23 ` Jens Axboe
2005-08-19 12:41 ` Alejandro Bonilla
[not found] ` <20050816200708.GE3425-l3A5Bk7waGM@public.gmane.org>
2005-08-24 21:44 ` Jon Escombe
2005-08-24 21:44 ` [Hdaps-devel] " Jon Escombe
2005-08-25 10:57 ` Alan Cox
2005-08-25 18:14 ` Jon Escombe
[not found] ` <430E0A84.8080809-Xbpc2PeERmvQXOPxS62xeg@public.gmane.org>
2005-08-26 6:49 ` Jens Axboe
2005-08-26 6:49 ` [Hdaps-devel] " Jens Axboe
-- strict thread matches above, loose matches on Subject: below --
2005-08-19 11:36 Stefan Rompf
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