From owner-freebsd-hackers Mon Jan 18 22:57:37 1999 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id WAA26288 for freebsd-hackers-outgoing; Mon, 18 Jan 1999 22:57:37 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from whistle.com (s205m131.whistle.com [207.76.205.131]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id WAA26280 for ; Mon, 18 Jan 1999 22:57:35 -0800 (PST) (envelope-from archie@whistle.com) Received: (from smap@localhost) by whistle.com (8.7.5/8.6.12) id WAA11998; Mon, 18 Jan 1999 22:56:56 -0800 (PST) Received: from bubba.whistle.com( 207.76.205.7) by whistle.com via smap (V2.0) id xma011996; Mon, 18 Jan 99 22:56:29 -0800 Received: (from archie@localhost) by bubba.whistle.com (8.8.7/8.6.12) id WAA09547; Mon, 18 Jan 1999 22:56:29 -0800 (PST) From: Archie Cobbs Message-Id: <199901190656.WAA09547@bubba.whistle.com> Subject: Re: Found problem w/ Paging performance over NFS In-Reply-To: <199901190128.RAA84794@apollo.backplane.com> from Matthew Dillon at "Jan 18, 99 05:28:35 pm" To: dillon@apollo.backplane.com (Matthew Dillon) Date: Mon, 18 Jan 1999 22:56:29 -0800 (PST) Cc: hackers@FreeBSD.ORG X-Mailer: ELM [version 2.4ME+ PL38 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Matthew Dillon writes: > Ok. I just figured out the interaction -- in fact, we *can't* test m->busy > in this section of code because of the following sequence: > > vm_fault -> vnode_pager_getpages -> ffs_getpages -> ffs_read -> > cluster_read -> getblk -> allocbuf ( lockup ) > > ffs_getpages converts the PG_BUSY into a vm_page_t->busy before getting into > the cluster stuff, and thus allocbuf() deep down cannot sleep on > vm_page_t->busy. > > Ick. I'm going to add a comment explaining that case. Yow. I don't think it's possible to overcomment the VM subsystem.. :-) -Archie ___________________________________________________________________________ Archie Cobbs * Whistle Communications, Inc. * http://www.whistle.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message