From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx109.postini.com [74.125.245.109]) by kanga.kvack.org (Postfix) with SMTP id 8031B6B0039 for ; Sun, 14 Jul 2013 19:47:54 -0400 (EDT) Received: from /spool/local by e23smtp06.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 15 Jul 2013 09:40:14 +1000 Received: from d23relay05.au.ibm.com (d23relay05.au.ibm.com [9.190.235.152]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id 1BCA12BB0051 for ; Mon, 15 Jul 2013 09:47:45 +1000 (EST) Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r6ENWM9d54591520 for ; Mon, 15 Jul 2013 09:32:23 +1000 Received: from d23av04.au.ibm.com (loopback [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r6ENlh9G010323 for ; Mon, 15 Jul 2013 09:47:43 +1000 Date: Mon, 15 Jul 2013 07:47:42 +0800 From: Wanpeng Li Subject: Re: [v5][PATCH 1/6] mm: swap: defer clearing of page_private() for swap cache pages Message-ID: <20130714234741.GA23628@hacker.(null)> Reply-To: Wanpeng Li References: <20130603200202.7F5FDE07@viggo.jf.intel.com> <20130603200204.C481DA6D@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130603200204.C481DA6D@viggo.jf.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mgorman@suse.de, tim.c.chen@linux.intel.com, minchan@kernel.org On Mon, Jun 03, 2013 at 01:02:04PM -0700, Dave Hansen wrote: > >From: Dave Hansen > >This patch defers the destruction of swapcache-specific data in >'struct page'. This simplifies the code because we do not have >to keep extra copies of the data during the removal of a page >from the swap cache. > >There are only two callers of swapcache_free() which actually >pass in a non-NULL 'struct page'. Both of them (__remove_mapping >and delete_from_swap_cache()) create a temporary on-stack >'swp_entry_t' and set entry.val to page_private(). > >They need to do this since __delete_from_swap_cache() does >set_page_private(page, 0) and destroys the information. > >However, I'd like to batch a few of these operations on several >pages together in a new version of __remove_mapping(), and I >would prefer not to have to allocate temporary storage for each >page. The code is pretty ugly, and it's a bit silly to create >these on-stack 'swp_entry_t's when it is so easy to just keep the >information around in 'struct page'. > >There should not be any danger in doing this since we are >absolutely on the path of freeing these page. There is no >turning back, and no other rerferences can be obtained after it >comes out of the radix tree. > >Note: This patch is separate from the next one since it >introduces the behavior change. I've seen issues with this patch >by itself in various forms and I think having it separate like >this aids bisection. > >Signed-off-by: Dave Hansen >Acked-by: Mel Gorman >Reviewed-by: Minchan Kin Reviewed-by: Wanpeng Li >--- > > linux.git-davehans/mm/swap_state.c | 4 ++-- > linux.git-davehans/mm/vmscan.c | 2 ++ > 2 files changed, 4 insertions(+), 2 deletions(-) > >diff -puN mm/swap_state.c~__delete_from_swap_cache-dont-clear-page-private mm/swap_state.c >--- linux.git/mm/swap_state.c~__delete_from_swap_cache-dont-clear-page-private 2013-06-03 12:41:30.321703206 -0700 >+++ linux.git-davehans/mm/swap_state.c 2013-06-03 12:41:30.326703428 -0700 >@@ -148,8 +148,6 @@ void __delete_from_swap_cache(struct pag > entry.val = page_private(page); > address_space = swap_address_space(entry); > radix_tree_delete(&address_space->page_tree, page_private(page)); >- set_page_private(page, 0); >- ClearPageSwapCache(page); > address_space->nrpages--; > __dec_zone_page_state(page, NR_FILE_PAGES); > INC_CACHE_INFO(del_total); >@@ -226,6 +224,8 @@ void delete_from_swap_cache(struct page > spin_unlock_irq(&address_space->tree_lock); > > swapcache_free(entry, page); >+ set_page_private(page, 0); >+ ClearPageSwapCache(page); > page_cache_release(page); > } > >diff -puN mm/vmscan.c~__delete_from_swap_cache-dont-clear-page-private mm/vmscan.c >--- linux.git/mm/vmscan.c~__delete_from_swap_cache-dont-clear-page-private 2013-06-03 12:41:30.323703296 -0700 >+++ linux.git-davehans/mm/vmscan.c 2013-06-03 12:41:30.328703516 -0700 >@@ -494,6 +494,8 @@ static int __remove_mapping(struct addre > __delete_from_swap_cache(page); > spin_unlock_irq(&mapping->tree_lock); > swapcache_free(swap, page); >+ set_page_private(page, 0); >+ ClearPageSwapCache(page); > } else { > void (*freepage)(struct page *); > >_ > >-- >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