Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758925Ab2FULCy (ORCPT ); Thu, 21 Jun 2012 07:02:54 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:40793 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758399Ab2FULCw convert rfc822-to-8bit (ORCPT ); Thu, 21 Jun 2012 07:02:52 -0400 MIME-Version: 1.0 In-Reply-To: <4FE2A937.6040701@kernel.org> References: <4FE169B1.7020600@kernel.org> <4FE16E80.9000306@gmail.com> <4FE18187.3050103@kernel.org> <4FE23069.5030702@gmail.com> <4FE26470.90401@kernel.org> <4FE27F15.8050102@kernel.org> <4FE2A937.6040701@kernel.org> Date: Thu, 21 Jun 2012 16:32:51 +0530 Message-ID: Subject: Re: Accounting problem of MIGRATE_ISOLATED freed page From: Aaditya Kumar To: Minchan Kim Cc: KOSAKI Motohiro , Mel Gorman , KAMEZAWA Hiroyuki , "linux-mm@kvack.org" , LKML , tim.bird@am.sony.com, frank.rowand@am.sony.com, takuzo.ohara@ap.sony.com, kan.iibuchi@jp.sony.com, aaditya.kumar@ap.sony.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10386 Lines: 293 On Thu, Jun 21, 2012 at 10:25 AM, Minchan Kim wrote: > On 06/21/2012 11:45 AM, KOSAKI Motohiro wrote: > >> On Wed, Jun 20, 2012 at 9:55 PM, Minchan Kim wrote: >>> On 06/21/2012 10:39 AM, KOSAKI Motohiro wrote: >>> >>>>>> number of isolate page block is almost always 0. then if we have such counter, >>>>>> we almost always can avoid zone->lock. Just idea. >>>>> >>>>> Yeb. I thought about it but unfortunately we can't have a counter for MIGRATE_ISOLATE. >>>>> Because we have to tweak in page free path for pages which are going to free later after we >>>>> mark pageblock type to MIGRATE_ISOLATE. >>>> >>>> I mean, >>>> >>>> if (nr_isolate_pageblock != 0) >>>> ? ?free_pages -= nr_isolated_free_pages(); // your counting logic >>>> >>>> return __zone_watermark_ok(z, alloc_order, mark, >>>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? classzone_idx, alloc_flags, free_pages); >>>> >>>> >>>> I don't think this logic affect your race. zone_watermark_ok() is already >>>> racy. then new little race is no big matter. >>> >>> >>> It seems my explanation wasn't enough. :( >>> I already understand your intention but we can't make nr_isolate_pageblock. >>> Because we should count two type of free pages. >> >> I mean, move_freepages_block increment number of page *block*, not pages. >> number of free *pages* are counted by zone_watermark_ok_safe(). >> >> >>> 1. Already freed page so they are already in buddy list. >>> ? Of course, we can count it with return value of move_freepages_block(zone, page, MIGRATE_ISOLATE) easily. >>> >>> 2. Will be FREEed page by do_migrate_range. >>> ? It's a _PROBLEM_. For it, we should tweak free path. No? >> >> No. >> >> >>> If All of pages are PageLRU when hot-plug happens(ie, 2), nr_isolate_pagblock is zero and >>> zone_watermk_ok_safe can't do his role. >> >> number of isolate pageblock don't depend on number of free pages. It's >> a concept of >> an attribute of PFN range. > > > It seems you mean is_migrate_isolate as a just flag, NOT nr_isolate_pageblock. > So do you mean this? > > diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h > index 3bdcab3..7f4d19c 100644 > --- a/include/linux/page-isolation.h > +++ b/include/linux/page-isolation.h > @@ -1,6 +1,7 @@ > ?#ifndef __LINUX_PAGEISOLATION_H > ?#define __LINUX_PAGEISOLATION_H > > +extern bool is_migrate_isolate; > ?/* > ?* Changes migrate type in [start_pfn, end_pfn) to be MIGRATE_ISOLATE. > ?* If specified range includes migrate types other than MOVABLE or CMA, > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index d2a515d..b997cb3 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1756,6 +1756,27 @@ bool zone_watermark_ok_safe(struct zone *z, int order, unsigned long ma > ? ? ? ?if (z->percpu_drift_mark && free_pages < z->percpu_drift_mark) > ? ? ? ? ? ? ? ?free_pages = zone_page_state_snapshot(z, NR_FREE_PAGES); > > +#if defined CONFIG_CMA || CONFIG_MEMORY_HOTPLUG > + ? ? ? if (unlikely(is_migrate_isolate)) { > + ? ? ? ? ? ? ? unsigned long flags; > + ? ? ? ? ? ? ? spin_lock_irqsave(&z->lock, flags); > + ? ? ? ? ? ? ? for (order = MAX_ORDER - 1; order >= 0; order--) { > + ? ? ? ? ? ? ? ? ? ? ? struct free_area *area = &z->free_area[order]; > + ? ? ? ? ? ? ? ? ? ? ? long count = 0; > + ? ? ? ? ? ? ? ? ? ? ? struct list_head *curr; > + > + ? ? ? ? ? ? ? ? ? ? ? list_for_each(curr, &area->free_list[MIGRATE_ISOLATE]) > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? count++; > + > + ? ? ? ? ? ? ? ? ? ? ? free_pages -= (count << order); > + ? ? ? ? ? ? ? ? ? ? ? if (free_pages < 0) { > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? free_pages = 0; > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? break; > + ? ? ? ? ? ? ? ? ? ? ? } > + ? ? ? ? ? ? ? } > + ? ? ? ? ? ? ? spin_unlock_irqrestore(&z->lock, flags); > + ? ? ? } > +#endif > ? ? ? ?return __zone_watermark_ok(z, order, mark, classzone_idx, alloc_flags, > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?free_pages); > ?} > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index c9f0477..212e526 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -19,6 +19,8 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages) > ? ? ? ?return pfn_to_page(pfn + i); > ?} > > +bool is_migrate_isolate = false; > + > ?/* > ?* start_isolate_page_range() -- make page-allocation-type of range of pages > ?* to be MIGRATE_ISOLATE. > @@ -43,6 +45,8 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, > ? ? ? ?BUG_ON((start_pfn) & (pageblock_nr_pages - 1)); > ? ? ? ?BUG_ON((end_pfn) & (pageblock_nr_pages - 1)); > > + ? ? ? is_migrate_isolate = true; > + > ? ? ? ?for (pfn = start_pfn; > ? ? ? ? ? ? pfn < end_pfn; > ? ? ? ? ? ? pfn += pageblock_nr_pages) { > @@ -59,6 +63,7 @@ undo: > ? ? ? ? ? ? pfn += pageblock_nr_pages) > ? ? ? ? ? ? ? ?unset_migratetype_isolate(pfn_to_page(pfn), migratetype); > > + ? ? ? is_migrate_isolate = false; > ? ? ? ?return -EBUSY; > ?} > > @@ -80,6 +85,9 @@ int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, > ? ? ? ? ? ? ? ? ? ? ? ?continue; > ? ? ? ? ? ? ? ?unset_migratetype_isolate(page, migratetype); > ? ? ? ?} > + > + ? ? ? is_migrate_isolate = false; > + > ? ? ? ?return 0; > ?} > ?/* > Hello Minchan, Sorry for delayed response. Instead of above how about something like this: diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h index 3bdcab3..fe9215f 100644 --- a/include/linux/page-isolation.h +++ b/include/linux/page-isolation.h @@ -34,4 +34,6 @@ extern int set_migratetype_isolate(struct page *page); extern void unset_migratetype_isolate(struct page *page, unsigned migratetype); +extern atomic_t is_migrate_isolated; + #endif diff --git a/mm/memory-failure.c b/mm/memory-failure.c index ab1e714..e076fa2 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1381,6 +1381,7 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags) * Isolate the page, so that it doesn't get reallocated if it * was free. */ + atomic_inc(&is_migrate_isolated); set_migratetype_isolate(p); /* * When the target page is a free hugepage, just remove it @@ -1406,6 +1407,7 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags) } unset_migratetype_isolate(p, MIGRATE_MOVABLE); unlock_memory_hotplug(); + atomic_dec(&is_migrate_isolated); return ret; } diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 0d7e3ec..cd7805c 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -892,6 +892,7 @@ static int __ref offline_pages(unsigned long start_pfn, nr_pages = end_pfn - start_pfn; /* set above range as isolated */ + atomic_inc(&is_migrate_isolated); ret = start_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE); if (ret) goto out; @@ -958,6 +959,7 @@ repeat: offline_isolated_pages(start_pfn, end_pfn); /* reset pagetype flags and makes migrate type to be MOVABLE */ undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE); + atomic_dec(&is_migrate_isolated); /* removal success */ zone->present_pages -= offlined_pages; zone->zone_pgdat->node_present_pages -= offlined_pages; @@ -986,6 +988,7 @@ failed_removal: undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE); out: + atomic_dec(&is_migrate_isolated); unlock_memory_hotplug(); return ret; } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 4403009..f549361 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1632,6 +1632,28 @@ bool zone_watermark_ok_safe(struct zone *z, int order, unsigned long mark, if (z->percpu_drift_mark && free_pages < z->percpu_drift_mark) free_pages = zone_page_state_snapshot(z, NR_FREE_PAGES); +#if defined CONFIG_CMA || CONFIG_MEMORY_HOTPLUG + if (unlikely(atomic_read(is_migrate_isolated)) { + unsigned long flags; + spin_lock_irqsave(&z->lock, flags); + for (order = MAX_ORDER - 1; order >= 0; order--) { + struct free_area *area = &z->free_area[order]; + long count = 0; + struct list_head *curr; + + list_for_each(curr, &area->free_list[MIGRATE_ISOLATE]) + count++; + + free_pages -= (count << order); + if (free_pages < 0) { + free_pages = 0; + break; + } + } + spin_unlock_irqrestore(&z->lock, flags); + } +#endif + return __zone_watermark_ok(z, order, mark, classzone_idx, alloc_flags, free_pages); } @@ -5785,6 +5807,7 @@ int alloc_contig_range(unsigned long start, unsigned long end, * put back to page allocator so that buddy can use them. */ + atomic_inc(&is_migrate_isolated); ret = start_isolate_page_range(pfn_max_align_down(start), pfn_max_align_up(end), migratetype); if (ret) @@ -5854,6 +5877,7 @@ int alloc_contig_range(unsigned long start, unsigned long end, done: undo_isolate_page_range(pfn_max_align_down(start), pfn_max_align_up(end), migratetype); + atomic_dec(&is_migrate_isolated); return ret; } diff --git a/mm/page_isolation.c b/mm/page_isolation.c index c9f0477..e8eb241 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -19,6 +19,8 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages) return pfn_to_page(pfn + i); } +atomic_t is_migrate_isolated; + /* * start_isolate_page_range() -- make page-allocation-type of range of pages * to be MIGRATE_ISOLATE. > It is still racy as you already mentioned and I don't think it's trivial. > Direct reclaim can't wake up kswapd forever by current fragile zone->all_unreclaimable. > So it's a livelock. > Then, do you want to fix this problem by your patch[1]? > > It could solve the livelock by OOM kill if we apply your patch[1] but still doesn't wake up > kswapd although it's not critical. Okay. Then, please write down this problem in detail > in your patch's changelog and resend, please. > > [1] http://lkml.org/lkml/2012/6/14/74 > > -- > Kind regards, > Minchan Kim -- 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/