From owner-freebsd-fs@freebsd.org Sat Aug 8 11:09:13 2015 Return-Path: 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 5A3F19B57CE for ; Sat, 8 Aug 2015 11:09:13 +0000 (UTC) (envelope-from wjw@digiware.nl) 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 41B7BC for ; Sat, 8 Aug 2015 11:09:13 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: by mailman.ysv.freebsd.org (Postfix) id 3E9289B57CD; Sat, 8 Aug 2015 11:09:13 +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 3D2F79B57CC for ; Sat, 8 Aug 2015 11:09:13 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: from smtp.digiware.nl (smtp.digiware.nl [31.223.170.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id EF407B for ; Sat, 8 Aug 2015 11:09:12 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: from rack1.digiware.nl (unknown [127.0.0.1]) by smtp.digiware.nl (Postfix) with ESMTP id 92C8B15344D; Sat, 8 Aug 2015 13:09:09 +0200 (CEST) X-Virus-Scanned: amavisd-new at digiware.nl Received: from smtp.digiware.nl ([127.0.0.1]) by rack1.digiware.nl (rack1.digiware.nl [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id YPgb8gqH2v5L; Sat, 8 Aug 2015 13:08:59 +0200 (CEST) Received: from [192.168.10.10] (asus [192.168.10.10]) by smtp.digiware.nl (Postfix) with ESMTPA id 523421534C0; Sat, 8 Aug 2015 13:08:59 +0200 (CEST) Subject: Re: Using SSDs as swap To: Konstantin Belousov References: <55C5D48E.6010605@digiware.nl> <20150808102900.GA2072@kib.kiev.ua> Cc: fs@freebsd.org From: Willem Jan Withagen Message-ID: <55C5E34B.9010905@digiware.nl> Date: Sat, 8 Aug 2015 13:08:59 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <20150808102900.GA2072@kib.kiev.ua> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 08 Aug 2015 11:09:13 -0000 On 8-8-2015 12:29, Konstantin Belousov wrote: > On Sat, Aug 08, 2015 at 12:06:06PM +0200, Willem Jan Withagen wrote: >> 2) Does the SSD "suffer" unneeded from swapping on it? > Depends on your swapping activity, but yes, I believe that intense swapping > would wear SSD in the short time. Would it be more intense than being beaten to death as a ARC cache?? If I look at most of my systems I try to prevent them even using really swap since that usually kills performance big time... So things get swapped out under pressure, but rarely get swapped back in, because the LRU properties of that part of the application minimise that chance of things getting paged back in. So the number of times that swap actually gets used is rather seldom. In writting swap, how are the allocations made where things are swapped. Do things always end up in a lineair order on swap writting things as close to the start as slots in swap allow it. SSD would profit from it being sort of a circular buffer... (Guess I have to try and understand the swap code.... ) --WjW