From owner-freebsd-fs@freebsd.org  Sat Aug  8 18:26:43 2015
Return-Path: <owner-freebsd-fs@freebsd.org>
Delivered-To: freebsd-fs@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 D4B889B5D77
 for <freebsd-fs@mailman.ysv.freebsd.org>; Sat,  8 Aug 2015 18:26:43 +0000 (UTC)
 (envelope-from wblock@wonkity.com)
Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org
 [IPv6:2001:1900:2254:206a::50:5])
 by mx1.freebsd.org (Postfix) with ESMTP id BAA2DBB7
 for <freebsd-fs@freebsd.org>; Sat,  8 Aug 2015 18:26:43 +0000 (UTC)
 (envelope-from wblock@wonkity.com)
Received: by mailman.ysv.freebsd.org (Postfix)
 id B7B589B5D76; Sat,  8 Aug 2015 18:26:43 +0000 (UTC)
Delivered-To: fs@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 B74C79B5D75
 for <fs@mailman.ysv.freebsd.org>; Sat,  8 Aug 2015 18:26:43 +0000 (UTC)
 (envelope-from wblock@wonkity.com)
Received: from wonkity.com (wonkity.com [67.158.26.137])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client CN "wonkity.com", Issuer "wonkity.com" (not verified))
 by mx1.freebsd.org (Postfix) with ESMTPS id 7952BBB6
 for <fs@freebsd.org>; Sat,  8 Aug 2015 18:26:43 +0000 (UTC)
 (envelope-from wblock@wonkity.com)
Received: from wonkity.com (localhost [127.0.0.1])
 by wonkity.com (8.15.2/8.15.2) with ESMTPS id t78IQdGH042727
 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO);
 Sat, 8 Aug 2015 12:26:39 -0600 (MDT)
 (envelope-from wblock@wonkity.com)
Received: from localhost (wblock@localhost)
 by wonkity.com (8.15.2/8.15.2/Submit) with ESMTP id t78IQcJ5042720;
 Sat, 8 Aug 2015 12:26:39 -0600 (MDT)
 (envelope-from wblock@wonkity.com)
Date: Sat, 8 Aug 2015 12:26:38 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
To: Willem Jan Withagen <wjw@digiware.nl>
cc: Konstantin Belousov <kostikbel@gmail.com>, fs@freebsd.org
Subject: Re: Using SSDs as swap
In-Reply-To: <55C60441.7040906@digiware.nl>
Message-ID: <alpine.BSF.2.20.1508081222371.53526@wonkity.com>
References: <55C5D48E.6010605@digiware.nl> <20150808102900.GA2072@kib.kiev.ua>
 <55C5E34B.9010905@digiware.nl> <20150808113750.GC2072@kib.kiev.ua>
 <55C60441.7040906@digiware.nl>
User-Agent: Alpine 2.20 (BSF 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII; format=flowed
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.4.3
 (wonkity.com [127.0.0.1]); Sat, 08 Aug 2015 12:26:39 -0600 (MDT)
X-BeenThere: freebsd-fs@freebsd.org
X-Mailman-Version: 2.1.20
Precedence: list
List-Id: Filesystems <freebsd-fs.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-fs>,
 <mailto:freebsd-fs-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-fs/>
List-Post: <mailto:freebsd-fs@freebsd.org>
List-Help: <mailto:freebsd-fs-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-fs>,
 <mailto:freebsd-fs-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 08 Aug 2015 18:26:43 -0000

On Sat, 8 Aug 2015, Willem Jan Withagen wrote:
>
> So perhaps the nicest thing to do for the SSDs is TRIM swap at
> startup??? So the the SSD controller van do its garbage collection and
> then keep the remainder of the stuff as it is.

This can be done now by using a swap file on a UFS partition with trim 
enabled.  The catch is that the swap file has to be deleted and 
recreated to trigger the trim.  The delete is quick, but the create 
depends on the size of the file and the speed of the hardware.  (And no, 
sparse files do not work as swap files.)

Maybe rotate swap files like log files, so they could be created when 
the system is idle.