Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750799AbXBNRR7 (ORCPT ); Wed, 14 Feb 2007 12:17:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750793AbXBNRR7 (ORCPT ); Wed, 14 Feb 2007 12:17:59 -0500 Received: from x35.xmailserver.org ([64.71.152.41]:1361 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750799AbXBNRR6 (ORCPT ); Wed, 14 Feb 2007 12:17:58 -0500 X-AuthUser: davidel@xmailserver.org Date: Wed, 14 Feb 2007 09:17:50 -0800 (PST) From: Davide Libenzi X-X-Sender: davide@alien.or.mcafeemobile.com To: Ingo Molnar cc: Evgeniy Polyakov , Benjamin LaHaise , Alan , Linux Kernel Mailing List , Linus Torvalds , Arjan van de Ven , Christoph Hellwig , Andrew Morton , Ulrich Drepper , Zach Brown , "David S. Miller" , Suparna Bhattacharya , Thomas Gleixner Subject: Re: [patch 00/11] ANNOUNCE: "Syslets", generic asynchronous system call support In-Reply-To: <20070214103731.GB6801@elte.hu> Message-ID: References: <20060529212109.GA2058@elte.hu> <20070213142010.GA638@elte.hu> <20070213150019.4b4d4827@localhost.localdomain> <20070213145848.GS18311@kvack.org> <20070213165642.GB16394@elte.hu> <20070213185636.GA23987@2ka.mipt.ru> <20070213221810.GF22104@elte.hu> <20070214085939.GA4665@2ka.mipt.ru> <20070214103731.GB6801@elte.hu> X-GPG-FINGRPRINT: CFAE 5BEE FD36 F65E E640 56FE 0974 BF23 270F 474E X-GPG-PUBLIC_KEY: http://www.xmailserver.org/davidel.asc MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1660 Lines: 39 On Wed, 14 Feb 2007, Ingo Molnar wrote: > > * Evgeniy Polyakov wrote: > > > Let me clarify what I meant. There is only limited number of threads, > > which are supposed to execute blocking context, so when all they are > > used, main one will block too - I asked about possibility to reuse the > > same thread to execute queue of requests attached to it, each request > > can block, but if blocking issue is removed, it would be possible to > > return. > > ah, ok, i understand your point. This is not quite possible: the > cachemisses are driven from schedule(), which can be arbitraily deep > inside arbitrary system calls. It can be in a mutex_lock() deep inside a > driver. It can be due to a alloc_pages() call done by a kmalloc() call > done from within ext3, which was called from the loopback block driver, > which was called from XFS, which was called from a VFS syscall. > > Even if it were possible to backtrack i'm quite sure we dont want to do > this, for three main reasons: IMO it'd be quite simple. We detect the service-thread full condition, *before* entering exec_atom and we queue the atom in an async_head request list. Yes, there is the chance that from the test time in sys_async_exec, to the time we'll end up entering exec_atom and down to schedule, one of the threads would become free, but IMO better that blocking sys_async_exec. - Davide - 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/