From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pigeon.gentoo.org ([208.92.234.80] helo=lists.gentoo.org) by finch.gentoo.org with esmtp (Exim 4.60) (envelope-from ) id 1QPHS4-0002Yo-4s for garchives@archives.gentoo.org; Wed, 25 May 2011 17:00:56 +0000 Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 6AFB71C185; Wed, 25 May 2011 16:58:10 +0000 (UTC) Received: from mail-bw0-f53.google.com (mail-bw0-f53.google.com [209.85.214.53]) by pigeon.gentoo.org (Postfix) with ESMTP id 0C9C31C185 for ; Wed, 25 May 2011 16:58:09 +0000 (UTC) Received: by bwg12 with SMTP id 12so9020788bwg.40 for ; Wed, 25 May 2011 09:58:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:from:to:subject:date:message-id:user-agent :in-reply-to:references:mime-version:content-transfer-encoding :content-type; bh=jEkV/CJDIL3cA+gCk/KkWkuEAJSSCcpRb5LgQ3pWs8A=; b=KHF48sAq7YlMiEyYETnxp2hqt59eZP+3IhE3oyX3zcZ1MKYnWqTnEi731inhoLrbfK TFCHkN6eTDseKq7mZHwPwybevvjdYCaM6HkH/9ktyD+aIUqUpUWRZ4srf2k6/1O8TKnR +RzeZC8eH49rLYEDwXOEtLkr2D7lVRM5FTeeU= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=from:to:subject:date:message-id:user-agent:in-reply-to:references :mime-version:content-transfer-encoding:content-type; b=UeXbS0WcsGwzN07O77IkG6I59iwEV7vngGq/eap3e7CXmixOAD1dIUNMRVgIKR1S85 PzeRDoaQF1w8txkW4zm8ut5AZXj2wj2Zsf0BdIuuM526V8/9Vxv6IkNaxL4fMbc5xOYy zWGSG1Z1BtU+P5lrclr32juiLE4gqZIQMIj/c= Received: by 10.205.83.3 with SMTP id ae3mr1029380bkc.71.1306342689169; Wed, 25 May 2011 09:58:09 -0700 (PDT) Received: from localhost.localnet (p4FC74796.dip0.t-ipconnect.de [79.199.71.150]) by mx.google.com with ESMTPS id 16sm5340936bkm.18.2011.05.25.09.58.07 (version=TLSv1/SSLv3 cipher=OTHER); Wed, 25 May 2011 09:58:08 -0700 (PDT) From: Volker Armin Hemmann To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] Swap performance Date: Wed, 25 May 2011 18:58:06 +0200 Message-ID: <3411637.6h55QLqd4n@localhost> User-Agent: KMail/4.6 rc1 (Linux/2.6.36.4r4; KDE/4.6.3; x86_64; ; ) In-Reply-To: References: <201105251621.00659.wonko@wonkology.org> Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Archives-Salt: X-Archives-Hash: 136f862827cfa3ceb4f33d4089e7310e On Wednesday 25 May 2011 10:31:19 Paul Hartman wrote: > When I move the swap to a slow SD card instead (2MB/sec transfer > rate), even in that slow device, swapoff on the eMMC swap partition > with ~500M in-use takes about 2 or 3 minutes at most with the data > being swapped slowly into the SD card. > > So I think in your case it should be much faster than that! you are comparing apples with oranges (harddisks with moving arms with solid state devices). Do yourself a favour. Look up how long a harddisk needs to position its head. Now you can calculate how many times a second a harddisk can position its head. Now remember: swap is stupid, so lots and lots of head movement needed (and a cash flush is running too - so even more movements to write all that crap to disk), The result: the whole mess is fscking slow. You can have a nice fat raid with nice and fast harddisks - if you try to stream to a 15 year old DLT drive with 5/10mb/sec speed the dlt drive will constantly rewind - because harddisks suck when they have to seek. And swap (just like a backup) = lots and lots and lots of seeks.