Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753809Ab3COCgE (ORCPT ); Thu, 14 Mar 2013 22:36:04 -0400 Received: from e23smtp08.au.ibm.com ([202.81.31.141]:45912 "EHLO e23smtp08.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753609Ab3COCgC (ORCPT ); Thu, 14 Mar 2013 22:36:02 -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 v3 2/5] zero-filled pages awareness Date: Fri, 15 Mar 2013 10:34:17 +0800 Message-Id: <1363314860-22731-3-git-send-email-liwanp@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1363314860-22731-1-git-send-email-liwanp@linux.vnet.ibm.com> References: <1363314860-22731-1-git-send-email-liwanp@linux.vnet.ibm.com> x-cbid: 13031502-5140-0000-0000-000002E51110 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6101 Lines: 213 Compression of zero-filled pages can unneccessarily cause internal fragmentation, and thus waste memory. This special case can be optimized. This patch captures zero-filled pages, and marks their corresponding zcache backing page entry as zero-filled. Whenever such zero-filled page is retrieved, we fill the page frame with zero. Acked-by: Dan Magenheimer Signed-off-by: Wanpeng Li --- drivers/staging/zcache/zcache-main.c | 81 +++++++++++++++++++++++++++++++--- 1 files changed, 75 insertions(+), 6 deletions(-) diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c index d73dd4b..6c35c7d 100644 --- a/drivers/staging/zcache/zcache-main.c +++ b/drivers/staging/zcache/zcache-main.c @@ -59,6 +59,12 @@ static inline void frontswap_tmem_exclusive_gets(bool b) } #endif +/* + * mark pampd to special value in order that later + * retrieve will identify zero-filled pages + */ +#define ZERO_FILLED 0x2 + /* enable (or fix code) when Seth's patches are accepted upstream */ #define zcache_writeback_enabled 0 @@ -543,7 +549,23 @@ static void *zcache_pampd_eph_create(char *data, size_t size, bool raw, { void *pampd = NULL, *cdata = data; unsigned clen = size; + bool zero_filled = false; struct page *page = (struct page *)(data), *newpage; + char *user_mem; + + user_mem = kmap_atomic(page); + + /* + * Compressing zero-filled pages will waste memory and introduce + * serious fragmentation, skip it to avoid overhead + */ + if (page_is_zero_filled(user_mem)) { + kunmap_atomic(user_mem); + clen = 0; + zero_filled = true; + goto got_pampd; + } + kunmap_atomic(user_mem); if (!raw) { zcache_compress(page, &cdata, &clen); @@ -592,6 +614,8 @@ got_pampd: zcache_eph_zpages_max = zcache_eph_zpages; if (ramster_enabled && raw) ramster_count_foreign_pages(true, 1); + if (zero_filled) + pampd = (void *)ZERO_FILLED; out: return pampd; } @@ -601,14 +625,31 @@ static void *zcache_pampd_pers_create(char *data, size_t size, bool raw, { void *pampd = NULL, *cdata = data; unsigned clen = size; + bool zero_filled = false; struct page *page = (struct page *)(data), *newpage; unsigned long zbud_mean_zsize; unsigned long curr_pers_zpages, total_zsize; + char *user_mem; if (data == NULL) { BUG_ON(!ramster_enabled); goto create_pampd; } + + user_mem = kmap_atomic(page); + + /* + * Compressing zero-filled pages will waste memory and introduce + * serious fragmentation, skip it to avoid overhead + */ + if (page_is_zero_filled(page)) { + kunmap_atomic(user_mem); + clen = 0; + zero_filled = true; + goto got_pampd; + } + kunmap_atomic(user_mem); + curr_pers_zpages = zcache_pers_zpages; /* FIXME CONFIG_RAMSTER... subtract atomic remote_pers_pages here? */ if (!raw) @@ -674,6 +715,8 @@ got_pampd: zcache_pers_zbytes_max = zcache_pers_zbytes; if (ramster_enabled && raw) ramster_count_foreign_pages(false, 1); + if (zero_filled) + pampd = (void *)ZERO_FILLED; out: return pampd; } @@ -735,7 +778,8 @@ out: */ void zcache_pampd_create_finish(void *pampd, bool eph) { - zbud_create_finish((struct zbudref *)pampd, eph); + if (pampd != (void *)ZERO_FILLED) + zbud_create_finish((struct zbudref *)pampd, eph); } /* @@ -780,6 +824,14 @@ static int zcache_pampd_get_data(char *data, size_t *sizep, bool raw, BUG_ON(preemptible()); BUG_ON(eph); /* fix later if shared pools get implemented */ BUG_ON(pampd_is_remote(pampd)); + + if (pampd == (void *)ZERO_FILLED) { + handle_zero_filled_page(data); + if (!raw) + *sizep = PAGE_SIZE; + return 0; + } + if (raw) ret = zbud_copy_from_zbud(data, (struct zbudref *)pampd, sizep, eph); @@ -801,12 +853,21 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw, struct tmem_oid *oid, uint32_t index) { int ret; - bool eph = !is_persistent(pool); + bool eph = !is_persistent(pool), zero_filled = false; struct page *page = NULL; unsigned int zsize, zpages; BUG_ON(preemptible()); BUG_ON(pampd_is_remote(pampd)); + + if (pampd == (void *)ZERO_FILLED) { + handle_zero_filled_page(data); + zero_filled = true; + if (!raw) + *sizep = PAGE_SIZE; + goto zero_fill; + } + if (raw) ret = zbud_copy_from_zbud(data, (struct zbudref *)pampd, sizep, eph); @@ -818,6 +879,7 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw, } page = zbud_free_and_delist((struct zbudref *)pampd, eph, &zsize, &zpages); +zero_fill: if (eph) { if (page) zcache_eph_pageframes = @@ -837,7 +899,7 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw, } if (!is_local_client(pool->client)) ramster_count_foreign_pages(eph, -1); - if (page) + if (page && !zero_filled) zcache_free_page(page); return ret; } @@ -851,16 +913,23 @@ static void zcache_pampd_free(void *pampd, struct tmem_pool *pool, { struct page *page = NULL; unsigned int zsize, zpages; + bool zero_filled = false; BUG_ON(preemptible()); - if (pampd_is_remote(pampd)) { + + if (pampd == (void *)ZERO_FILLED) + zero_filled = true; + + if (pampd_is_remote(pampd) && !zero_filled) { + BUG_ON(!ramster_enabled); pampd = ramster_pampd_free(pampd, pool, oid, index, acct); if (pampd == NULL) return; } if (is_ephemeral(pool)) { - page = zbud_free_and_delist((struct zbudref *)pampd, + if (!zero_filled) + page = zbud_free_and_delist((struct zbudref *)pampd, true, &zsize, &zpages); if (page) zcache_eph_pageframes = @@ -883,7 +952,7 @@ static void zcache_pampd_free(void *pampd, struct tmem_pool *pool, } if (!is_local_client(pool->client)) ramster_count_foreign_pages(is_ephemeral(pool), -1); - if (page) + if (page && !zero_filled) zcache_free_page(page); } -- 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/