From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx117.postini.com [74.125.245.117]) by kanga.kvack.org (Postfix) with SMTP id 5616F6B0005 for ; Sat, 16 Mar 2013 20:04:17 -0400 (EDT) Received: from /spool/local by e28smtp01.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sun, 17 Mar 2013 05:30:35 +0530 Received: from d28relay05.in.ibm.com (d28relay05.in.ibm.com [9.184.220.62]) by d28dlp01.in.ibm.com (Postfix) with ESMTP id 1DCDCE0059 for ; Sun, 17 Mar 2013 05:35:31 +0530 (IST) Received: from d28av01.in.ibm.com (d28av01.in.ibm.com [9.184.220.63]) by d28relay05.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r2H043dQ65142970 for ; Sun, 17 Mar 2013 05:34:04 +0530 Received: from d28av01.in.ibm.com (loopback [127.0.0.1]) by d28av01.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r2H046b8013467 for ; Sun, 17 Mar 2013 00:04:06 GMT Date: Sun, 17 Mar 2013 08:04:04 +0800 From: Wanpeng Li Subject: Re: [PATCH v3 2/5] zero-filled pages awareness Message-ID: <20130317000403.GA6169@hacker.(null)> Reply-To: Wanpeng Li References: <1363314860-22731-1-git-send-email-liwanp@linux.vnet.ibm.com> <1363314860-22731-3-git-send-email-liwanp@linux.vnet.ibm.com> <51447DC9.5070701@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51447DC9.5070701@oracle.com> Sender: owner-linux-mm@kvack.org List-ID: To: Bob Liu Cc: Greg Kroah-Hartman , Andrew Morton , Dan Magenheimer , Seth Jennings , Konrad Rzeszutek Wilk , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Sat, Mar 16, 2013 at 10:12:25PM +0800, Bob Liu wrote: > >On 03/15/2013 10:34 AM, Wanpeng Li wrote: >> 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); >> + > Hi Bob, >Maybe we can add a function for this code? It seems a bit duplicated. > Great point! I will introduce a separate function to handle zero filled capture stuff. Regards, Wanpeng Li >> 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); >> } >> >> > >-- >Regards, >-Bob > >-- >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 -- 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