Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756624Ab3CNKJG (ORCPT ); Thu, 14 Mar 2013 06:09:06 -0400 Received: from e23smtp09.au.ibm.com ([202.81.31.142]:60559 "EHLO e23smtp09.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755566Ab3CNKJE (ORCPT ); Thu, 14 Mar 2013 06:09:04 -0400 From: Wanpeng Li To: Greg Kroah-Hartman , Andrew Morton Cc: Dan Magenheimer , Seth Jennings , Konrad Rzeszutek Wilk , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wanpeng Li Subject: [PATCH v2 0/4] zcache: Support zero-filled pages more efficiently Date: Thu, 14 Mar 2013 18:08:13 +0800 Message-Id: <1363255697-19674-1-git-send-email-liwanp@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.5.4 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13031410-3568-0000-0000-0000034A0199 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2352 Lines: 67 Changelog: v1 -> v2: * avoid changing tmem.[ch] entirely, spotted by Dan. * don't accumulate [eph|pers]pageframe and [eph|pers]zpages for zero-filled pages, spotted by Dan * cleanup TODO list * add Dan Acked-by. Motivation: - Seth Jennings points out compress zero-filled pages with LZO(a lossless data compression algorithm) will waste memory and result in fragmentation. https://lkml.org/lkml/2012/8/14/347 - Dan Magenheimer add "Support zero-filled pages more efficiently" feature in zcache TODO list https://lkml.org/lkml/2013/2/13/503 Design: - For store page, capture zero-filled pages(evicted clean page cache pages and swap pages), but don't compress them, set pampd which store zpage address to 0x2(since 0x0 and 0x1 has already been ocuppied) to mark special zero-filled case and take advantage of tmem infrastructure to transform handle-tuple(pool id, object id, and an index) to a pampd. Twice compress zero-filled pages will contribute to one zcache_[eph|pers]_pageframes count accumulated. - For load page, traverse tmem hierachical to transform handle-tuple to pampd and identify zero-filled case by pampd equal to 0x2 when filesystem reads file pages or a page needs to be swapped in, then refill the page to zero and return. Test: dd if=/dev/zero of=zerofile bs=1MB count=500 vmtouch -t zerofile vmtouch -e zerofile formula: - fragmentation level = (zcache_[eph|pers]_pageframes * PAGE_SIZE - zcache_[eph|pers]_zbytes) * 100 / (zcache_[eph|pers]_pageframes * PAGE_SIZE) - memory zcache occupy = zcache_[eph|pers]_zbytes Result: without zero-filled awareness: - fragmentation level: 98% - memory zcache occupy: 238MB with zero-filled awareness: - fragmentation level: 0% - memory zcache occupy: 0MB Wanpeng Li (4): introduce zero-filled pages handler zero-filled pages awareness introduce zero-filled pages stat count clean TODO list drivers/staging/zcache/TODO | 3 +- drivers/staging/zcache/zcache-main.c | 119 ++++++++++++++++++++++++++++++++-- 2 files changed, 114 insertions(+), 8 deletions(-) -- 1.7.7.6 -- 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/