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Date: Thu, 25 Jun 2009 09:15:19 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Daniel Walker <dwalker@fifo99.com>
Cc: Linus Walleij <linus.ml.walleij@gmail.com>,
       Brian Swetland <swetland@google.com>,
       Arve =?ISO-8859-14?B?SGr4bm5lduVn?= <arve@android.com>,
       Jeremy Fitzhardinge <jeremy@goop.org>,
       Greg Kroah-Hartman <greg@kroah.com>, linux-kernel@vger.kernel.org,
       hackbod@android.com, Marcel Holtmann <marcel@holtmann.org>
Subject: Re: [PATCH 1/6] staging: android: binder: Remove some funny &&
 usage
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On Wed, 24 Jun 2009 17:20:19 -0700
Daniel Walker <dwalker@fifo99.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 ?