From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: async network I/O, event channels, etc Date: Thu, 27 Jul 2006 10:11:15 +0200 Message-ID: <20060727081114.GH5282@suse.de> References: <20060726062817.GA20636@2ka.mipt.ru> <20060726.231055.121220029.davem@davemloft.net> <20060727074902.GC5490@2ka.mipt.ru> <20060727.010255.87351515.davem@davemloft.net> <20060727080901.GG5282@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: johnpol@2ka.mipt.ru, drepper@redhat.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:28202 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S1750792AbWG0IL2 (ORCPT ); Thu, 27 Jul 2006 04:11:28 -0400 To: David Miller Content-Disposition: inline In-Reply-To: <20060727080901.GG5282@suse.de> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, Jul 27 2006, Jens Axboe wrote: > On Thu, Jul 27 2006, David Miller wrote: > > From: Evgeniy Polyakov > > Date: Thu, 27 Jul 2006 11:49:02 +0400 > > > > > I.e. map skb's data to userspace? Not a good idea especially with it's > > > tricky lifetime and unability for userspace to inform kernel when it > > > finished and skb can be freed (without additional syscall). > > > > Hmmm... > > > > If it is paged based, I do not see the problem. Events and calls to > > AIO I/O routines make transfer of buffer ownership. The fact that > > while kernel (and thus networking stack) "owns" the buffer for an AIO > > call, the user can have a valid mapping to it is a unimportant detail. > > Ownership may be clear, but "when can I reuse" is tricky. The same issue > comes up for vmsplice -> splice to socket. Ownership transition from user -> kernel that is, what I'm trying to say that returning ownership to the user again is the tricky part. -- Jens Axboe