From owner-freebsd-hackers@FreeBSD.ORG  Sat Oct  2 15:01:13 2004
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id 79FFC16A4CE; Sat,  2 Oct 2004 15:01:13 +0000 (GMT)
Received: from lara.cc.fer.hr (lara.cc.fer.hr [161.53.72.113])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id BA0D243D49; Sat,  2 Oct 2004 15:01:12 +0000 (GMT)
	(envelope-from ivoras@fer.hr)
Received: from [127.0.0.1] (localhost.cc.fer.hr [127.0.0.1])
	by lara.cc.fer.hr (8.13.1/8.13.1) with ESMTP id i92F0SsZ000753;
	Sat, 2 Oct 2004 17:00:28 +0200 (CEST)
	(envelope-from ivoras@fer.hr)
Message-ID: <415EC28B.4030900@fer.hr>
Date: Sat, 02 Oct 2004 17:00:27 +0200
From: Ivan Voras <ivoras@fer.hr>
User-Agent: Mozilla Thunderbird 0.7.3 (X11/20040923)
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: hackers@freebsd.org, current@freebsd.org
References: <415BDFC2.1020304@fer.hr> <415C9967.3090309@jonny.eng.br>
	<415D2E86.5060007@fer.hr> <20041002133512.GA16646@nerve.riss-telecom.ru>
In-Reply-To: <20041002133512.GA16646@nerve.riss-telecom.ru>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: GEOM (ggate) compression consumer +problem
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 02 Oct 2004 15:01:13 -0000

Dmitry Frolov wrote:
> * Ivan Voras <ivoras@fer.hr> [01.10.2004 17:17]:
> 
>>But, I still can't solve the wdrain problem. I've tried it on a recent 
>>BETA6 kernel and it still remains. Writes get slower and slower 
>>(actually, the frequency of writes), and then something locks up (with 
>>no CPU usage...). Sometimes, *any* writes to any filesystem lock up.
> 
> 
> Looks very similar to a syncing problem found in md(4).
> Take a look at cvs log entry for revision 1.115 of md.c:
> 
> http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/dev/md/md.c

Thank you! It's exactly the same problem I've got. After including 
O_DIRECT and O_FSYNC flags to the open() call, the problems dissapear 
(though performance takes a big hit).

Also, it's the same problem with ggatel. This small patch solves it:


--- ggatel.c.old        Sat Oct  2 16:48:08 2004
+++ ggatel.c    Sat Oct  2 16:48:11 2004
@@ -160,7 +160,7 @@
         struct g_gate_ctl_create ggioc;
         int fd;

-       fd = open(path, g_gate_openflags(flags));
+       fd = open(path, g_gate_openflags(flags) | O_DIRECT | O_FSYNC);
         if (fd < 0)
                 err(EXIT_FAILURE, "Cannot open %s", path);
         ggioc.gctl_version = G_GATE_VERSION;


I've poslihed some quirks from the ggatec, so it should now be ready for 
somewhat broader testing ;)

(It's at http://ivoras.sharanet.org/ggcomp.tgz ; expect about 10x worse 
performance compared to performance without compression).