On Fri, 18 Feb 2011 00:08:19 +0900 Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > Recently, there are reported problem about thrashing. > (http://marc.info/?l=rsync&m=128885034930933&w=2) > It happens by backup workloads(ex, nightly rsync). > That's because the workload makes just use-once pages > and touches pages twice. It promotes the page into > active list so that it results in working set page eviction. > > Some app developer want to support POSIX_FADV_NOREUSE. > But other OSes don't support it, either. > (http://marc.info/?l=linux-mm&m=128928979512086&w=2) > > By other approach, app developers use POSIX_FADV_DONTNEED. > But it has a problem. If kernel meets page is writing > during invalidate_mapping_pages, it can't work. > It makes for application programmer to use it since they always > have to sync data before calling fadivse(..POSIX_FADV_DONTNEED) to > make sure the pages could be discardable. At last, they can't use > deferred write of kernel so that they could see performance loss. > (http://insights.oetiker.ch/linux/fadvise.html) > > In fact, invalidation is very big hint to reclaimer. > It means we don't use the page any more. So let's move > the writing page into inactive list's head if we can't truncate > it right now. > > Why I move page to head of lru on this patch, Dirty/Writeback page > would be flushed sooner or later. It can prevent writeout of pageout > which is less effective than flusher's writeout. > > Originally, I reused lru_demote of Peter with some change so added > his Signed-off-by. > > Reported-by: Ben Gamari <bgamari.foss@xxxxxxxxx> > Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx> > Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Acked-by: Rik van Riel <riel@xxxxxxxxxx> > Acked-by: Mel Gorman <mel@xxxxxxxxx> > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Nick Piggin <npiggin@xxxxxxxxx> > Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> One question is ....it seems there is no flush() code for percpu pagevec in this patch. Is it safe against cpu hot plug ? And from memory hot unplug point of view, I'm grad if pagevec for this is flushed at the same time as when we clear other per-cpu lru pagevecs. (And compaction will be affected by the page_count() magic by pagevec which is flushed only when FADVISE is called.) Could you add add-on patches for flushing and hooks ? Thanks, -Kame > --- > Changelog since v4: > - Change function comments - suggested by Johannes > - Change function name - suggested by Johannes > - Drop only dirty/writeback pages to deactive pagevec - suggested by Johannes > - Add acked-by > > Changelog since v3: > - Change function comments - suggested by Johannes > - Change function name - suggested by Johannes > - add only dirty/writeback pages to deactive pagevec > > Changelog since v2: > - mapped page leaves alone - suggested by Mel > - pass part related PG_reclaim in next patch. > > Changelog since v1: > - modify description > - correct typo > - add some comment > > include/linux/swap.h | 1 + > mm/swap.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++ > mm/truncate.c | 17 ++++++++--- > 3 files changed, 91 insertions(+), 5 deletions(-) > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index 4d55932..c335055 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -215,6 +215,7 @@ extern void mark_page_accessed(struct page *); > extern void lru_add_drain(void); > extern int lru_add_drain_all(void); > extern void rotate_reclaimable_page(struct page *page); > +extern void deactivate_page(struct page *page); > extern void swap_setup(void); > > extern void add_page_to_unevictable_list(struct page *page); > diff --git a/mm/swap.c b/mm/swap.c > index c02f936..4aea806 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -39,6 +39,7 @@ int page_cluster; > > static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs); > static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs); > +static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs); > > /* > * This path almost never happens for VM activity - pages are normally > @@ -347,6 +348,60 @@ void add_page_to_unevictable_list(struct page *page) > } > > /* > + * If the page can not be invalidated, it is moved to the > + * inactive list to speed up its reclaim. It is moved to the > + * head of the list, rather than the tail, to give the flusher > + * threads some time to write it out, as this is much more > + * effective than the single-page writeout from reclaim. > + */ > +static void lru_deactivate(struct page *page, struct zone *zone) > +{ > + int lru, file; > + > + if (!PageLRU(page) || !PageActive(page)) > + return; > + > + /* Some processes are using the page */ > + if (page_mapped(page)) > + return; > + > + file = page_is_file_cache(page); > + lru = page_lru_base_type(page); > + del_page_from_lru_list(zone, page, lru + LRU_ACTIVE); > + ClearPageActive(page); > + ClearPageReferenced(page); > + add_page_to_lru_list(zone, page, lru); > + __count_vm_event(PGDEACTIVATE); > + > + update_page_reclaim_stat(zone, page, file, 0); > +} > + > +static void ____pagevec_lru_deactivate(struct pagevec *pvec) > +{ > + int i; > + struct zone *zone = NULL; > + > + for (i = 0; i < pagevec_count(pvec); i++) { > + struct page *page = pvec->pages[i]; > + struct zone *pagezone = page_zone(page); > + > + if (pagezone != zone) { > + if (zone) > + spin_unlock_irq(&zone->lru_lock); > + zone = pagezone; > + spin_lock_irq(&zone->lru_lock); > + } > + lru_deactivate(page, zone); > + } > + if (zone) > + spin_unlock_irq(&zone->lru_lock); > + > + release_pages(pvec->pages, pvec->nr, pvec->cold); > + pagevec_reinit(pvec); > +} > + > + > +/* > * Drain pages out of the cpu's pagevecs. > * Either "cpu" is the current CPU, and preemption has already been > * disabled; or "cpu" is being hot-unplugged, and is already dead. > @@ -372,6 +427,29 @@ static void drain_cpu_pagevecs(int cpu) > pagevec_move_tail(pvec); > local_irq_restore(flags); > } > + > + pvec = &per_cpu(lru_deactivate_pvecs, cpu); > + if (pagevec_count(pvec)) > + ____pagevec_lru_deactivate(pvec); > +} > + > +/** > + * deactivate_page - forcefully deactivate a page > + * @page: page to deactivate > + * > + * This function hints the VM that @page is a good reclaim candidate, > + * for example if its invalidation fails due to the page being dirty > + * or under writeback. > + */ > +void deactivate_page(struct page *page) > +{ > + if (likely(get_page_unless_zero(page))) { > + struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs); > + > + if (!pagevec_add(pvec, page)) > + ____pagevec_lru_deactivate(pvec); > + put_cpu_var(lru_deactivate_pvecs); > + } > } > > void lru_add_drain(void) > diff --git a/mm/truncate.c b/mm/truncate.c > index 4d415b3..9ec7bc5 100644 > --- a/mm/truncate.c > +++ b/mm/truncate.c > @@ -328,11 +328,12 @@ EXPORT_SYMBOL(truncate_inode_pages); > * pagetables. > */ > unsigned long invalidate_mapping_pages(struct address_space *mapping, > - pgoff_t start, pgoff_t end) > + pgoff_t start, pgoff_t end) > { > struct pagevec pvec; > pgoff_t next = start; > - unsigned long ret = 0; > + unsigned long ret; > + unsigned long count = 0; > int i; > > pagevec_init(&pvec, 0); > @@ -359,8 +360,14 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping, > if (lock_failed) > continue; > > - ret += invalidate_inode_page(page); > - > + ret = invalidate_inode_page(page); > + /* > + * Invalidation is a hint that the page is no longer > + * of interest and try to speed up its reclaim. > + */ > + if (!ret) > + deactivate_page(page); > + count += ret; > unlock_page(page); > if (next > end) > break; > @@ -369,7 +376,7 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping, > mem_cgroup_uncharge_end(); > cond_resched(); > } > - return ret; > + return count; > } > EXPORT_SYMBOL(invalidate_mapping_pages); > > -- > 1.7.1 > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . 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