From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <46D6CC35.90207@aitel.hist.no> Date: Thu, 30 Aug 2007 15:55:01 +0200 From: Helge Hafting MIME-Version: 1.0 Subject: Re: speeding up swapoff References: <46D61F48.5090406@shaw.ca> In-Reply-To: <46D61F48.5090406@shaw.ca> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Robert Hancock Cc: Daniel Drake , Arjan van de Ven , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: Robert Hancock wrote: > Daniel Drake wrote: >> On Wed, 2007-08-29 at 07:30 -0700, Arjan van de Ven wrote: >>>> My experiments show that when there is not much free physical memory, >>>> swapoff moves pages out of swap at a rate of approximately 5mb/sec. >>> sounds like about disk speed (at random-seek IO pattern) >> >> We are only using 'standard' seagate SATA disks, but I would have >> thought much more performance (40+ mb/sec) would be reachable. > > Not if it is doing random seeks.. If the swap device is full, then there is no need for random seeks as the swap pages can be read in disk order. A not so full swap will skip over the unused areas, the time needed should still be limited to the time needed for reading the whole swap device. If this optimization is worth it is another problem though. Helge Hafting -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org