From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qe0-f49.google.com (mail-qe0-f49.google.com [209.85.128.49]) by kanga.kvack.org (Postfix) with ESMTP id 9D7176B0031 for ; Wed, 20 Nov 2013 22:50:48 -0500 (EST) Received: by mail-qe0-f49.google.com with SMTP id w7so1286779qeb.8 for ; Wed, 20 Nov 2013 19:50:48 -0800 (PST) Received: from mail-qa0-x235.google.com (mail-qa0-x235.google.com [2607:f8b0:400d:c00::235]) by mx.google.com with ESMTPS id ko6si9766506qeb.85.2013.11.20.19.50.47 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 20 Nov 2013 19:50:47 -0800 (PST) Received: by mail-qa0-f53.google.com with SMTP id j5so2774507qaq.5 for ; Wed, 20 Nov 2013 19:50:47 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <528D570D.3020006@oracle.com> References: <1384976973-32722-1-git-send-email-ddstreet@ieee.org> <528D570D.3020006@oracle.com> Date: Thu, 21 Nov 2013 11:50:47 +0800 Message-ID: Subject: Re: [PATCH v2] mm/zswap: change zswap to writethrough cache From: Weijie Yang Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Bob Liu Cc: Dan Streetman , Seth Jennings , linux-mm@kvack.org, linux-kernel , Minchan Kim , Weijie Yang Hello Dan, On Thu, Nov 21, 2013 at 8:42 AM, Bob Liu wrote: > Hi Dan, > > On 11/21/2013 03:49 AM, Dan Streetman wrote: >> Currently, zswap is writeback cache; stored pages are not sent >> to swap disk, and when zswap wants to evict old pages it must >> first write them back to swap cache/disk manually. This avoids >> swap out disk I/O up front, but only moves that disk I/O to >> the writeback case (for pages that are evicted), and adds the >> overhead of having to uncompress the evicted pages, and adds the >> need for an additional free page (to store the uncompressed page) >> at a time of likely high memory pressure. Additionally, being >> writeback adds complexity to zswap by having to perform the >> writeback on page eviction. >> > > Good work! > >> This changes zswap to writethrough cache by enabling >> frontswap_writethrough() before registering, so that any >> successful page store will also be written to swap disk. All the >> writeback code is removed since it is no longer needed, and the >> only operation during a page eviction is now to remove the entry >> from the tree and free it. >> Thanks for your work. I reviewed this patch, and it is good to me. However, I am skeptical about it because: 1. it will add more IO than original zswap, how does it result in a performance improvement ? 2. most embedded device use NAND, more IO will reduce its working life Regards > Could you do some testing using eg. SPECjbb? And compare the result with > original zswap. > > Thanks, > -Bob > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- 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