Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756025Ab3CMHGH (ORCPT ); Wed, 13 Mar 2013 03:06:07 -0400 Received: from e28smtp07.in.ibm.com ([122.248.162.7]:44637 "EHLO e28smtp07.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755955Ab3CMHF6 (ORCPT ); Wed, 13 Mar 2013 03:05:58 -0400 From: Wanpeng Li To: Andrew Morton Cc: Greg Kroah-Hartman , Dan Magenheimer , Seth Jennings , Konrad Rzeszutek Wilk , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wanpeng Li Subject: [PATCH 0/4] zcache: Support zero-filled pages more efficiently Date: Wed, 13 Mar 2013 15:05:17 +0800 Message-Id: <1363158321-20790-1-git-send-email-liwanp@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.5.4 X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13031307-8878-0000-0000-0000063E21E7 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2216 Lines: 60 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 add pageframes count once compress zero-filled pages twice drivers/staging/zcache/tmem.c | 4 +- drivers/staging/zcache/tmem.h | 5 + drivers/staging/zcache/zcache-main.c | 141 +++++++++++++++++++++++++++++++--- 3 files changed, 139 insertions(+), 11 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/