From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx198.postini.com [74.125.245.198]) by kanga.kvack.org (Postfix) with SMTP id 25FEE6B0069 for ; Fri, 17 Aug 2012 18:32:38 -0400 (EDT) Received: from /spool/local by e4.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 17 Aug 2012 18:32:37 -0400 Received: from d01relay03.pok.ibm.com (d01relay03.pok.ibm.com [9.56.227.235]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id 9A00C6E803C for ; Fri, 17 Aug 2012 18:32:34 -0400 (EDT) Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by d01relay03.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q7HMWYE3112308 for ; Fri, 17 Aug 2012 18:32:34 -0400 Received: from d01av03.pok.ibm.com (loopback [127.0.0.1]) by d01av03.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q7HMWYHL025131 for ; Fri, 17 Aug 2012 19:32:34 -0300 Message-ID: <502EC67F.4070603@linux.vnet.ibm.com> Date: Fri, 17 Aug 2012 17:32:31 -0500 From: Seth Jennings MIME-Version: 1.0 Subject: Re: [PATCH 0/3] staging: zcache+ramster: move to new code base and re-merge References: <1345156293-18852-1-git-send-email-dan.magenheimer@oracle.com> <20120816224814.GA18737@kroah.com> <9f2da295-4164-4e95-bbe8-bd234307b83c@default> <20120816230817.GA14757@kroah.com> In-Reply-To: <20120816230817.GA14757@kroah.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Greg KH Cc: Dan Magenheimer , devel@linuxdriverproject.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ngupta@vflare.org, Konrad Wilk , minchan@kernel.org On 08/16/2012 06:08 PM, Greg KH wrote: > On a larger note, I _really_ don't want a set of 'delete and then add it > back' set of patches. That destroys all of the work that people had > done up until now on the code base. > > I understand your need, and want, to start fresh, but you still need to > abide with the "evolve over time" model here. Surely there is some path > from the old to the new codebase that you can find? I very much agree that this is the wrong way to do this. I can't possibly inspect the code changes in this format, so I'll just comment on some high level changes and mention some performance results. I like frontswap reclaiming memory from cleancache. I think that would work better than having the pages go back to the kernel-wide page pool using the shrinker interface. That being said, I can't test the impact of this alone because all these changes are being submitted together. I also like the sysfs->debugfs cleanup and zbud being moved into its own file. I do _not_ support replacing zsmalloc with zbud: https://lkml.org/lkml/2012/8/14/347 I do not support the integration of ramster mixed in with all the rest of these changes. I have no way to see or measure the impact of the ramster code. I ran my kernel building benchmark twice on an unmodified v3.5 kernel with zcache and then with these changes. On none-low memory pressure, <16 threads, they worked roughly the same with low swap volume. However, in mid-high pressure, >20 threads, these changes degraded zcache runtime and I/O savings by 30-80%. I would suspect the low-density storage of zbud as the culprit; however I can't confirm this because, again, it all one huge change. Some smaller issues: 1. This patchset breaks the build when CONFIG_SWAP in not set. FRONTSWAP depends on SWAP, but ZCACHE _selects_ FRONTSWAP. If ZCACHE is selected and FRONTSWAP can't be selected because SWAP isn't selected, then there is a break. 2. I get about 8 unsued/uninit'ed variable warnings at compile time. So I can't support this patchset, citing the performance degradation and the fact that this submission is unreviewable due to it being one huge monolithic patchset on top of an existing codebase. Seth -- 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