Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758916Ab3GRMnx (ORCPT ); Thu, 18 Jul 2013 08:43:53 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:21931 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757881Ab3GRMnw (ORCPT ); Thu, 18 Jul 2013 08:43:52 -0400 Message-ID: <51E7E2FC.3070807@oracle.com> Date: Thu, 18 Jul 2013 20:43:40 +0800 From: Bob Liu User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130221 Thunderbird/17.0.3 MIME-Version: 1.0 To: Martin Steigerwald CC: Seth Jennings , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: zswap: How to determine whether it is compressing swap pages? References: <1674223.HVFdAhB7u5@merkaba> <3337744.IgTT2hGPE5@merkaba> <20130717143834.GA4379@variantweb.net> <3125575.Ki4S75m1kx@merkaba> In-Reply-To: <3125575.Ki4S75m1kx@merkaba> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1604 Lines: 42 Hi Martin, On 07/18/2013 03:38 AM, Martin Steigerwald wrote: > Am Mittwoch, 17. Juli 2013, 09:38:34 schrieb Seth Jennings: >> On Wed, Jul 17, 2013 at 01:41:44PM +0200, Martin Steigerwald wrote: >>> Is there any way to run zcache concurrently with zswap? I.e. use zcache only >>> for read caches for filesystem and zswap for swap? >> >> No, at least not with zcache's frontswap features enabled. frontswap is a very >> simple API that allows only one "backend" to register with it at a time. So >> that means _either_ zswap or zcache. >> >> The only way they can be used in a meaningful way together is to use the >> "nofrontswap" zcache option in the kernel boot parameters to prevent >> zcache overriding zswap's frontswap registration. >> >> But the general answer is no, they shouldn't be used together. >> >> >>> >>> What is better suited for swap? zswap or zcache? >> >> zswap targets the specific case of caching swapped out pages in a compressed >> cache and this is much simpler than zcache. zswap is also in mainline as of >> 3.11-rc1. > > Thanks. > > Okay, then I will test zswap for now. I have a nice use case for it: Playing Could you make some test by kernel compiling? Something like kernbench. During my testing, I found that the swap ins/outs operations reduced but the kernel compile time didn't reduce accordingly. -- Regards, -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/