Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933039AbXAaRsT (ORCPT ); Wed, 31 Jan 2007 12:48:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932955AbXAaRsT (ORCPT ); Wed, 31 Jan 2007 12:48:19 -0500 Received: from agminet01.oracle.com ([141.146.126.228]:48659 "EHLO agminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933039AbXAaRsT (ORCPT ); Wed, 31 Jan 2007 12:48:19 -0500 In-Reply-To: References: <1170209044.26655.364.camel@localhost.localdomain> Mime-Version: 1.0 (Apple Message framework v752.3) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <1FB0094B-4B45-4749-8855-5AFD1A26085D@oracle.com> Cc: Benjamin Herrenschmidt , Linux Kernel Mailing List , linux-aio@kvack.org, Suparna Bhattacharya , Benjamin LaHaise , Ingo Molnar Content-Transfer-Encoding: 7bit From: Zach Brown Subject: Re: [PATCH 0 of 4] Generic AIO by scheduling stacks Date: Wed, 31 Jan 2007 09:47:42 -0800 To: Linus Torvalds X-Mailer: Apple Mail (2.752.3) X-Brightmail-Tracker: AAAAAQAAAAI= X-Whitelist: TRUE Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1494 Lines: 37 > Does that mean that we might not have some cases where we'd need to > make > sure we do things differently? Of course not. Something migt show up. Might, and has. For a good time, take journal_info out of per_call_chain() in the patch set and watch it helpfully and loudly wet itself. There really really are bits of thread_struct which are strictly thread-local-storage, of a sort, for a kernel call path. Sharing them, even only through cooperate scheduling, is fatal. link_count is another obvious one. They're also the only ones I've bothered to discover so far :). > But > this actually makes it very clear what the difference between "struct > thread_struct" and "struct task_struct" are. One is shared between > fibrils, the other isn't. Indeed. Right now the per-fibril uses of task_struct members are left inline in task_struct and are copied on fibril switches. We *could* put them in thread_info, at the cost of stack pressure, or hang them off task_struct in their own struct to avoid the copies, at the cost of indirection. I didn't like imposing a cost on paths that don't use fibrils, though, so I left them inline. (I think you know all this. I'm clarifying for the peanut gallery, I hope.) - z - 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/