Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751287AbWJEPHz (ORCPT ); Thu, 5 Oct 2006 11:07:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751488AbWJEPHz (ORCPT ); Thu, 5 Oct 2006 11:07:55 -0400 Received: from berlioz.imada.sdu.dk ([130.225.128.12]:8120 "EHLO berlioz.imada.sdu.dk") by vger.kernel.org with ESMTP id S1751287AbWJEPHx (ORCPT ); Thu, 5 Oct 2006 11:07:53 -0400 From: Hans Henrik Happe To: Evgeniy Polyakov Subject: Re: [take19 1/4] kevent: Core files. Date: Thu, 5 Oct 2006 17:07:48 +0200 User-Agent: KMail/1.9.1 Cc: Eric Dumazet , Ulrich Drepper , lkml , David Miller , Ulrich Drepper , Andrew Morton , netdev , Zach Brown , Christoph Hellwig , Chase Venters , Johann Borck References: <11587449471424@2ka.mipt.ru> <200610051601.20701.hhh@imada.sdu.dk> <20061005141556.GA30715@2ka.mipt.ru> In-Reply-To: <20061005141556.GA30715@2ka.mipt.ru> MIME-Version: 1.0 Content-Type: text/plain; charset="koi8-r" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200610051707.49087.hhh@imada.sdu.dk> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2062 Lines: 46 On Thursday 05 October 2006 16:15, Evgeniy Polyakov wrote: > On Thu, Oct 05, 2006 at 04:01:19PM +0200, Hans Henrik Happe (hhh@imada.sdu.dk) wrote: > > > And what happens when there are 3 empty at the beginning and \we need to > > > put there 4 ready events? > > > > Couldn't there be 3 areas in the mmap buffer: > > > > - Unused: entries that the kernel can alloc from. > > - Alloced: entries alloced by kernel but not yet used by user. Kernel can > > update these if new events requires that. > > - Consumed: entries that the user are processing. > > > > The user takes a set of alloced entries and make them consumed. Then it > > processes the events after which it makes them unused. > > > > If there are no unused entries and the kernel needs some, it has wait for free > > entries. The user has to notify when unused entries becomes available. It > > could set a flag in the mmap'ed area to avoid unnessesary wakeups. > > > > The are some details with indexing and wakeup notification that I have left > > out, but I hope my idea is clear. I could give a more detailed description if > > requested. Also, I'm a user-level programmer so I might not get the whole > > picture. > > This looks good on a picture, but how can you put it into page-based > storage without major and complex shared structures, which should be > properly locked between kernelspace and userspace? I wasn't clear about the structure. I meant a ring-buffer with 3 areas. So it's basically the same model as Eric Dumazet described, only with 3 indexes; 2 in the user-writeable page and 1 in kernel. When the kernel has alloced an entry it should store it in a way that makes it invalid after user consumsion, which is simply an increment of an index. Sliding-window like schemes should solve this. Hans Henrik Happe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/