From owner-freebsd-hackers@freebsd.org Sat Aug 12 15:23:12 2017 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id E7867DDD1FC for ; Sat, 12 Aug 2017 15:23:12 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: from mail-io0-x22b.google.com (mail-io0-x22b.google.com [IPv6:2607:f8b0:4001:c06::22b]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id B7DAB64D02 for ; Sat, 12 Aug 2017 15:23:12 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: by mail-io0-x22b.google.com with SMTP id c74so28291014iod.4 for ; Sat, 12 Aug 2017 08:23:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bsdimp-com.20150623.gappssmtp.com; s=20150623; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to:cc; bh=KwO/XVBpOG7QTfik8pt8RmLifkNZKiSd91RRNBg8IRk=; b=PGxIv3SQOznX6n6BcXseYcntjC5r00YadA36o3jWnX7vG4j5jpj5Of7z50jqYiB1rw JM1poHe0mlQ3zW+0ZA6LOIPAdEGFfb4ae+jufb7jQHR71brRB0efMXuEDRny0XUUmkay qCbjM8uAJ0We5k2aZrGmLHRWrdg1YpkOaymjI9BGk1WnL2UttwPBxYLlg5K+IV79ndg6 cNzaUUMXY5iAgzCLcHWdeyziLpVCbg/Gm9LQjyui5kMCyLqH5w1BKqZW0VFjgwVG6bKk TnX9rpWcen9j/iGifvxhMm1xPU0BHYHQU1X5Tw6njZcKLJCdd2NCiOt+M0HZoL0MFsJl 69vQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to:cc; bh=KwO/XVBpOG7QTfik8pt8RmLifkNZKiSd91RRNBg8IRk=; b=e1ur8n7Ii+vUrwXuDPP+ll6FkiWvjHk9DTQYv1X8HRWylS7BbsTVZe6Vxv4NILUtlD FqEGVzVTIKeTqsHDKt0ODlobPxJuE1PTtV/kensDWTrUqJFETiJyleP9unW7lF3ywY9w eQJtXaxdpY6frf3bhj36akTMRjr7fryfc0SJx0dulbFilyuCE2ZNFDhZaI48j3s7MATX fllnsLozIdEIUa+guWRGqumG/jI3m7o4pLc7fp3JhDKaq8NAuk7Kpq1okof+mACTlk8r D7sWGTEERInwUfoQ2xp7xjJFZLvS9j/1RGbCRT2qtlxqFXSusPI/co0VynBOh9DNMAFi sphA== X-Gm-Message-State: AIVw112j0uoMerlxCwOGfZjUIqUXd2n2Ag+5duaLfoEQ7YPBXDn/4l7T y7VmZYqZrImfxX7t/62qrNfImVvcwxvT X-Received: by 10.107.145.2 with SMTP id t2mr15283396iod.160.1502551391893; Sat, 12 Aug 2017 08:23:11 -0700 (PDT) MIME-Version: 1.0 Sender: wlosh@bsdimp.com Received: by 10.79.10.71 with HTTP; Sat, 12 Aug 2017 08:23:11 -0700 (PDT) X-Originating-IP: [2603:300b:6:5100:e113:b8b8:d4d8:acf3] In-Reply-To: References: <598ADB65.8060701@grosbein.net> From: Warner Losh Date: Sat, 12 Aug 2017 09:23:11 -0600 X-Google-Sender-Auth: tVgrs3Z4yk1vwvkkwhFAGQejQKI Message-ID: Subject: Re: Freebsd 11.0 - system freeze on intensive I/O To: Gautam Cc: freebsd-hackers , "gautam@execve.net" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.23 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 12 Aug 2017 15:23:13 -0000 On Fri, Aug 11, 2017 at 11:17 PM, Gautam wrote: > Hi, > > On Wed, Aug 9, 2017 at 10:23 PM, Gautam wrote: > > > Hi, > > > > I just want to comment, that when I tested it there > > was absolutely no need for any swap usage. I tried the test on a laptop > > with 8GB RAM and > > did it from the console mode. But it does seem that there might be some > > request (read/write) to swap which > > =E2=80=8Bcauses a lock up to the system.=E2=80=8B > > > > =E2=80=8BOne update on this one. I installed a custom stable/11 kernel = and world > (sched =3D 4BSD was the only change), and the problem > is no longer seen. From my untrained eyes, it looks like some kind of swa= p > request starvation causing a hang when ULE is in use.=E2=80=8B > I did some patches a few years ago that separated out geom requests into their own uma map, if you wanted and hacked the swap pager to use that to ensure that it always had BIOs available to do it's I/O. Maybe I should dust them off and see if they help you. They didn't seem to help me too much, but didn't hurt too much either. There's still the issue of some drivers not pre-allocating requests, which is what makes the deadlock possible in the first place. Warner