Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753993AbYFRLhd (ORCPT ); Wed, 18 Jun 2008 07:37:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752910AbYFRLhZ (ORCPT ); Wed, 18 Jun 2008 07:37:25 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:37446 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752841AbYFRLhX (ORCPT ); Wed, 18 Jun 2008 07:37:23 -0400 Date: Wed, 18 Jun 2008 20:36:52 +0900 From: KOSAKI Motohiro To: KAMEZAWA Hiroyuki Subject: Re: [Experimental][PATCH] putback_lru_page rework Cc: kosaki.motohiro@jp.fujitsu.com, Daisuke Nishimura , Andrew Morton , Rik van Riel , Lee Schermerhorn , Nick Piggin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-testers@vger.kernel.org In-Reply-To: <20080618184000.a855dfe0.kamezawa.hiroyu@jp.fujitsu.com> References: <20080617164709.de4db070.nishimura@mxp.nes.nec.co.jp> <20080618184000.a855dfe0.kamezawa.hiroyu@jp.fujitsu.com> Message-Id: <20080618195009.37BF.KOSAKI.MOTOHIRO@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.42 [ja] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8435 Lines: 310 Hi kame-san, > putback_lru_page() in this patch has a new concepts. > When it adds page to unevictable list, it checks the status is > changed or not again. if changed, retry to putback. it seems good idea :) this patch can reduce lock_page() call. > - } else if (page_evictable(page, NULL)) { > - /* > - * For evictable pages, we can use the cache. > - * In event of a race, worst case is we end up with an > - * unevictable page on [in]active list. > - * We know how to handle that. > - */ I think this comment is useful. Why do you want kill it? > +redo: > + lru = !!TestClearPageActive(page); > + if (page_evictable(page, NULL)) { > lru += page_is_file_cache(page); > lru_cache_add_lru(page, lru); > - mem_cgroup_move_lists(page, lru); > -#ifdef CONFIG_UNEVICTABLE_LRU > - if (was_unevictable) > - count_vm_event(NORECL_PGRESCUED); > -#endif > } else { > - /* > - * Put unevictable pages directly on zone's unevictable > - * list. > - */ ditto. > + lru = LRU_UNEVICTABLE; > add_page_to_unevictable_list(page); > - mem_cgroup_move_lists(page, LRU_UNEVICTABLE); > -#ifdef CONFIG_UNEVICTABLE_LRU > - if (!was_unevictable) > - count_vm_event(NORECL_PGCULLED); > -#endif > } > + mem_cgroup_move_lists(page, lru); > + > + /* > + * page's status can change while we move it among lru. If an evictable > + * page is on unevictable list, it never be freed. To avoid that, > + * check after we added it to the list, again. > + */ > + if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { > + if (!isolate_lru_page(page)) { > + put_page(page); > + goto redo; No. We should treat carefully unevictable -> unevictable moving too. > + } > + /* This means someone else dropped this page from LRU > + * So, it will be freed or putback to LRU again. There is > + * nothing to do here. > + */ > + } > + > + if (was_unevictable && lru != LRU_UNEVICTABLE) > + count_vm_event(NORECL_PGRESCUED); > + else if (!was_unevictable && lru == LRU_UNEVICTABLE) > + count_vm_event(NORECL_PGCULLED); > > put_page(page); /* drop ref from isolate */ > - return ret; /* ret => "page still locked" */ > } > - > -/* > - * Cull page that shrink_*_list() has detected to be unevictable > - * under page lock to close races with other tasks that might be making > - * the page evictable. Avoid stranding an evictable page on the > - * unevictable list. > - */ > -static void cull_unevictable_page(struct page *page) > +#else > +void putback_lru_page(struct page *page) > { > - lock_page(page); > - if (putback_lru_page(page)) > - unlock_page(page); > + int lru; > + VM_BUG_ON(PageLRU(page)); > + > + lru = !!TestClearPageActive(page) + page_is_file_cache(page); > + lru_cache_add_lru(page, lru); > + mem_cgroup_move_lists(page, lru); > + put_page(page); > } > +#endif > > /* > * shrink_page_list() returns the number of reclaimed pages > @@ -746,8 +736,8 @@ free_it: > continue; > > cull_mlocked: > - if (putback_lru_page(page)) > - unlock_page(page); > + unlock_page(page); > + putback_lru_page(page); > continue; > > activate_locked: > @@ -1127,7 +1117,7 @@ static unsigned long shrink_inactive_lis > list_del(&page->lru); > if (unlikely(!page_evictable(page, NULL))) { > spin_unlock_irq(&zone->lru_lock); > - cull_unevictable_page(page); > + putback_lru_page(page); > spin_lock_irq(&zone->lru_lock); > continue; > } > @@ -1231,7 +1221,7 @@ static void shrink_active_list(unsigned > list_del(&page->lru); > > if (unlikely(!page_evictable(page, NULL))) { > - cull_unevictable_page(page); > + putback_lru_page(page); > continue; > } > > @@ -2393,8 +2383,6 @@ int zone_reclaim(struct zone *zone, gfp_ > int page_evictable(struct page *page, struct vm_area_struct *vma) > { > > - VM_BUG_ON(PageUnevictable(page)); > - > if (mapping_unevictable(page_mapping(page))) > return 0; Why do you remove this? > @@ -169,7 +166,8 @@ static int __mlock_vma_pages_range(struc > > /* > * get_user_pages makes pages present if we are > - * setting mlock. > + * setting mlock. and this extra reference count will > + * disable migration of this page. > */ > ret = get_user_pages(current, mm, addr, > min_t(int, nr_pages, ARRAY_SIZE(pages)), > @@ -197,14 +195,8 @@ static int __mlock_vma_pages_range(struc > for (i = 0; i < ret; i++) { > struct page *page = pages[i]; > > - /* > - * page might be truncated or migrated out from under > - * us. Check after acquiring page lock. > - */ > - lock_page(page); > - if (page->mapping) > + if (page_mapcount(page)) > mlock_vma_page(page); > - unlock_page(page); > put_page(page); /* ref from get_user_pages() */ > > /* > @@ -240,6 +232,9 @@ static int __munlock_pte_handler(pte_t * > struct page *page; > pte_t pte; > > + /* > + * page is never be unmapped by page-reclaim. we lock this page now. > + */ > retry: > pte = *ptep; > /* > @@ -261,7 +256,15 @@ retry: > goto out; > > lock_page(page); > - if (!page->mapping) { > + /* > + * Because we lock page here, we have to check 2 cases. > + * - the page is migrated. > + * - the page is truncated (file-cache only) > + * Note: Anonymous page doesn't clear page->mapping even if it > + * is removed from rmap. > + */ > + if (!page->mapping || > + (PageAnon(page) && !page_mapcount(page))) { > unlock_page(page); > goto retry; > } > Index: test-2.6.26-rc5-mm3/mm/migrate.c > =================================================================== > --- test-2.6.26-rc5-mm3.orig/mm/migrate.c > +++ test-2.6.26-rc5-mm3/mm/migrate.c > @@ -67,9 +67,7 @@ int putback_lru_pages(struct list_head * > > list_for_each_entry_safe(page, page2, l, lru) { > list_del(&page->lru); > - lock_page(page); > - if (putback_lru_page(page)) > - unlock_page(page); > + putback_lru_page(page); > count++; > } > return count; > @@ -571,7 +569,6 @@ static int fallback_migrate_page(struct > static int move_to_new_page(struct page *newpage, struct page *page) > { > struct address_space *mapping; > - int unlock = 1; > int rc; > > /* > @@ -610,12 +607,11 @@ static int move_to_new_page(struct page > * Put back on LRU while holding page locked to > * handle potential race with, e.g., munlock() > */ this comment isn't true. > - unlock = putback_lru_page(newpage); > + putback_lru_page(newpage); > } else > newpage->mapping = NULL; originally move_to_lru() called in unmap_and_move(). unevictable infrastructure patch move to this point for calling putback_lru_page() under page locked. So, your patch remove page locked dependency. move to unmap_and_move() again is better. it become page lock holding time reducing. > > - if (unlock) > - unlock_page(newpage); > + unlock_page(newpage); > > return rc; > } > @@ -632,7 +628,6 @@ static int unmap_and_move(new_page_t get > struct page *newpage = get_new_page(page, private, &result); > int rcu_locked = 0; > int charge = 0; > - int unlock = 1; > > if (!newpage) > return -ENOMEM; > @@ -713,6 +708,7 @@ rcu_unlock: > rcu_read_unlock(); > > unlock: > + unlock_page(page); > > if (rc != -EAGAIN) { > /* > @@ -722,18 +718,9 @@ unlock: > * restored. > */ > list_del(&page->lru); > - if (!page->mapping) { > - VM_BUG_ON(page_count(page) != 1); > - unlock_page(page); > - put_page(page); /* just free the old page */ > - goto end_migration; > - } else > - unlock = putback_lru_page(page); > + putback_lru_page(page); > } > > - if (unlock) > - unlock_page(page); > - > end_migration: > if (!charge) > mem_cgroup_end_migration(newpage); > Index: test-2.6.26-rc5-mm3/mm/internal.h > =================================================================== > --- test-2.6.26-rc5-mm3.orig/mm/internal.h > +++ test-2.6.26-rc5-mm3/mm/internal.h > @@ -43,7 +43,7 @@ static inline void __put_page(struct pag > * in mm/vmscan.c: > */ > extern int isolate_lru_page(struct page *page); > -extern int putback_lru_page(struct page *page); > +extern void putback_lru_page(struct page *page); > > /* > * in mm/page_alloc.c > -- 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/