Date: Fri, 14 Jul 2000 15:29:35 +0200 From: Sheldon Hearn <sheldonh@uunet.co.za> To: hackers@FreeBSD.org Subject: Re: Where is the syncer kernel process implemented? Message-ID: <67168.963581375@axl.ops.uunet.co.za> In-Reply-To: Your message of "Fri, 14 Jul 2000 14:32:11 %2B0200." <66316.963577931@axl.ops.uunet.co.za>
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On Fri, 14 Jul 2000 14:32:11 +0200, Sheldon Hearn wrote: > I need to replace the update(4) manual page with a syncer(4) manual > page. Can someone please point me at the code that implements this > process? Alfred Perlstein pointed me at the correct code. I used the update(4) manual page as a starting point and came up with this after a fairly lazy glance at the code. Does it look alright? Ciao, Sheldon. .\" Copyright (c) 2000 Sheldon Hearn <sheldonh@FreeBSD.org> .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $FreeBSD$ .\" .Dd July 14, 2000 .Dt SYNCER 4 .Os .Sh NAME .Nm syncer .Nd filesystem synchronizer kernel process .Sh SYNOPSIS .Nm syncer .Sh DESCRIPTION The .Nm kernel process helps protect the integrity of disk volumes by flushing volatile cached filesystem data to disk. This is done at thirty second .Pq actually Dv SYNCER_MAXDELAY - 2 intervals by default. .Pp The kernel places all .Xr vnode 9 Ns 's in a number of queues equal to .Dv SYNCER_MAXDELAY . The .Nm process works through the queues in a round-robin fashion, usually processing one queue per second. For each .Xr vnode 9 on the queue, the .Nm process forces a write out to disk of its dirty buffers. .Sh SEE ALSO .Xr sync 2 , .Xr fsck 8 , .Xr sync 8 .Sh BUGS It is possible on some systems that a .Xr sync 2 occurring simultaneously with a crash may cause file system damage. See .Xr fsck 8 . .Sh HISTORY The .Nm process is a descendant of the update command, which apeared in .At v6 , and was usually started by .Pa /etc/rc when the system went multi-user. A kernel initiated update process first appeared in .Fx 2.0 . To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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