Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763417Ab3DCKQj (ORCPT ); Wed, 3 Apr 2013 06:16:39 -0400 Received: from e28smtp07.in.ibm.com ([122.248.162.7]:46488 "EHLO e28smtp07.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758732Ab3DCKQh (ORCPT ); Wed, 3 Apr 2013 06:16:37 -0400 From: Wanpeng Li To: Greg Kroah-Hartman Cc: Andrew Morton , Dan Magenheimer , Seth Jennings , Konrad Rzeszutek Wilk , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven , Fengguang Wu , Wanpeng Li Subject: [PATCH part2 v6 0/3] staging: zcache: Support zero-filled pages more efficiently Date: Wed, 3 Apr 2013 18:16:20 +0800 Message-Id: <1364984183-9711-1-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: 13040310-8878-0000-0000-0000068ECEF4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3210 Lines: 84 Changelog: v5 -> v6: * shove variables in debug.c and in debug.h just have an extern, spotted by Konrad * update patch description, spotted by Konrad v4 -> v5: * fix compile error, reported by Fengguang, Geert * add check for !is_ephemeral(pool), spotted by Bob v3 -> v4: * handle duplication in page_is_zero_filled, spotted by Bob * fix zcache writeback in dubugfs * fix pers_pageframes|_max isn't exported in debugfs * fix static variable defined in debug.h but used in multiple C files * rebase on Greg's staging-next v2 -> v3: * increment/decrement zcache_[eph|pers]_zpages for zero-filled pages, spotted by Dan * replace "zero" or "zero page" by "zero_filled_page", spotted by Dan 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 (3): staging: zcache: fix static variables defined in debug.h but used in mutiple C files staging: zcache: introduce zero-filled page stat count staging: zcache: clean TODO list drivers/staging/zcache/TODO | 3 +- drivers/staging/zcache/debug.c | 35 +++++++++++++++ drivers/staging/zcache/debug.h | 79 ++++++++++++++++++++------------- drivers/staging/zcache/zcache-main.c | 4 ++ 4 files changed, 88 insertions(+), 33 deletions(-) -- 1.7.5.4 -- 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/