From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 27 Oct 2000 16:44:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 27 Oct 2000 16:44:09 -0400 Received: from fw.SuSE.com ([202.58.118.35]:45817 "EHLO linux.local") by vger.kernel.org with ESMTP id ; Fri, 27 Oct 2000 16:44:06 -0400 Date: Fri, 27 Oct 2000 13:46:03 -0700 From: Jens Axboe To: Rui Sousa Cc: Rik van Riel , linux-kernel@vger.kernel.org Subject: Re: Blocked processes <=> Elevator starvation? Message-ID: <20001027134603.A513@suse.de> In-Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: ; from rsousa@grad.physics.sunysb.edu on Fri, Oct 27, 2000 at 05:22:01PM +0100 X-OS: Linux 2.4.0-test10 i686 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 27 2000, Rui Sousa wrote: > I finally had time to give this a better look. It now seems the problem > is in the VM system. > > I patched a test10-pre4 kernel with kdb, then started two "diff -ur > linux-2.4.0testX linux-2.4.0testY > log1" and two "find / -true > > log". After this I tried cat"ing" a small file. The cat never > returned. At this point I entered kdb and did a stack trace on the "cat" > process: > > schedule() > ___wait_on_page() > do_generic_file_read() > generic_file_read() > sys_read() > system_call() > > So it seems the process is either in a loop in ___wait_on_page() > racing for the PageLock or it never wakes-up... (I guess I could add a > printk to check which) > Unfortunately I didn't find anything obviously wrong with the code. > I hope you can do a better job tracking the problem down. Rik is right, just because you are seeing long waits on wait_on_page doesn't make it a vm problem. When a I/O on a page completes, the page will be unlocked and wait_on_page can grab it -- so I/O stalls would results in this behaviour. Could you try this patch: *.kernel.org/pub/linux/kernel/people/axboe/patches/2.4.0-test10-pre6/blk-7.bz2 and see if it makes a difference? -- * Jens Axboe * SuSE Labs - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/