linux-kernel - Re: [PATCH 1/6] staging: android: binder: Remove some funny && usage

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Message-ID: <20090625091519.23bc42ff@lxorguk.ukuu.org.uk>
Date:	Thu, 25 Jun 2009 09:15:19 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Daniel Walker <dwalker@...o99.com>
Cc:	Linus Walleij <linus.ml.walleij@...il.com>,
	Brian Swetland <swetland@...gle.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Greg Kroah-Hartman <greg@...ah.com>,
	linux-kernel@...r.kernel.org, hackbod@...roid.com,
	Marcel Holtmann <marcel@...tmann.org>
Subject: Re: [PATCH 1/6] staging: android: binder: Remove some funny &&
 usage

On Wed, 24 Jun 2009 17:20:19 -0700
Daniel Walker <dwalker@...o99.com> wrote:

> On Thu, 2009-06-25 at 02:01 +0200, Linus Walleij wrote:
> 
> > What I really want to know, is how this relates to the vmsplice() and
> > other zero-copy buffer passing schemes already in the kernel. I was
> > sort of dreaming that D-Bus and other IPC could be accelerated on
> > top of that.
> 
> Marcel had mentioned earlier in this thread that D-Bus could be
> accelerated with shared memory or moving the dbus-daemon into the
> kernel. splice() and vmplice() seem like fairly robust system calls. I
> would think they could be used also ..

Except for very large amounts of data what makes you think zero copy
buffer passing will be fast ? TLB shootdowns are expensive and they scale
horribly badly with threaded apps on multiprocessor systems ?
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