From owner-freebsd-arch@FreeBSD.ORG Fri Jun 1 21:42:41 2012 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 4ADA7106566B; Fri, 1 Jun 2012 21:42:41 +0000 (UTC) (envelope-from giovanni.trematerra@gmail.com) Received: from mail-qa0-f47.google.com (mail-qa0-f47.google.com [209.85.216.47]) by mx1.freebsd.org (Postfix) with ESMTP id B57408FC15; Fri, 1 Jun 2012 21:42:40 +0000 (UTC) Received: by qabg1 with SMTP id g1so677010qab.13 for ; Fri, 01 Jun 2012 14:42:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=1b+jNglZtbxjmC/T2jxHqzQUByHT4QP3SQaqaclj0LA=; b=UxZZFTPtRZLOfjplU5Vter32S+ZMyTi1K5bFSf7LvXxeIjwz6RHrv16Oduj/vg8AaE dyVvGfAtQ1DMoV49dyldbiqVBaVDFWv2QWzCR26Fu2T6debRcfTy7dvjVoVn2vVl4xZs 4ae6n2ff3Yo1y2DBNqn7V6iztPTVEUNZ35w9MvYYrXGmT2MRqYl8Ixed3E2u49/c259R fuVHJn/q0ySp5Rnuv23nQvaODt0eraUn1WgpVhR94WfT3j/YwWaZSaeHLnAypulpJePP ZF3b6gjlmx7enPjSDAtLzxRj6yr2c13G5yacQz8SVHnXf7Nb1UGW6FYK3EBoF/+fD0vb DZaQ== MIME-Version: 1.0 Received: by 10.224.181.134 with SMTP id by6mr5853096qab.56.1338586954256; Fri, 01 Jun 2012 14:42:34 -0700 (PDT) Received: by 10.229.160.20 with HTTP; Fri, 1 Jun 2012 14:42:34 -0700 (PDT) In-Reply-To: <20120601193522.GA2358@deviant.kiev.zoral.com.ua> References: <20120601193522.GA2358@deviant.kiev.zoral.com.ua> Date: Fri, 1 Jun 2012 23:42:34 +0200 Message-ID: From: Giovanni Trematerra To: Konstantin Belousov Content-Type: text/plain; charset=ISO-8859-1 Cc: Attilio Rao , alc@freebsd.org, Alexander Kabaev , freebsd-arch@freebsd.org Subject: Re: [RFC] Kernel shared variables X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 01 Jun 2012 21:42:41 -0000 On Fri, Jun 1, 2012 at 9:35 PM, Konstantin Belousov wrote: > On Fri, Jun 01, 2012 at 07:53:15PM +0200, Giovanni Trematerra wrote: >> Hello, >> I'd like to discuss a way to provide a mechanism to share some read-only >> data between kernel and user space programs avoiding syscall overhead, >> implementing some them, such as gettimeofday(3) and time(3) as ordinary >> user space routine. >> >> The patch at >> http://www.trematerra.net/patches/ksvar_experimental.patch >> > > I very much dislike what you described, it makes ABI maintanence > a nightmare. While I respect your decision to dislike my work, could you please give me some concrete examples of ABI maintenance nightmare? I mean not based on speculation. > Below is some mail I wrote around Spring 2009, making some notes about > desired proposal. I wonder why your proposal isn't on the Ideas Page wiki. By the way, is this proposal valid? http://wiki.freebsd.org/IdeasPage#Avoiding_syscall_overhead_.28GSoC.29 > This is what called vdso in Linux land. I know what vdso is in Linux land but while implementing vdso will give us some additional features in any case it needs a mechanism like the one I implemented (ksvar) to access kernel data while in user space and I think my implementation isn't too much different from what is called VVAR in linux parlance. Please take a look at http://fxr.watson.org/fxr/source/arch/x86/include/asm/vvar.h?v=linux-2.6 http://fxr.watson.org/fxr/source/arch/x86/vdso/vclock_gettime.c?v=linux-2.6;im=10 Could you please review the kernel part of the patch? -- Gianni