Hi Mel, On Tue, Nov 23, 2010 at 6:28 PM, Mel Gorman <mel@xxxxxxxxx> wrote: > On Sun, Nov 21, 2010 at 11:30:23PM +0900, Minchan Kim 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 developer uses POSIX_FADV_DONTNEED. >> But it has a problem. If kernel meets page is writing >> during invalidate_mapping_pages, it can't work. >> It is very hard for application programmer to use it. >> Because 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, invalidate 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 it is real working set, it could have a enough time to >> activate the page since we always try to keep many pages in >> inactive list. >> >> I reuse lru_demote of Peter with some change. >> >> Reported-by: Ben Gamari <bgamari.foss@xxxxxxxxx> >> Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx> >> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> >> Cc: Rik van Riel <riel@xxxxxxxxxx> >> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> >> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> >> Cc: Nick Piggin <npiggin@xxxxxxxxx> >> >> Ben, Remain thing is to modify rsync and use >> fadvise(POSIX_FADV_DONTNEED). Could you test it? >> --- >> include/linux/swap.h | 1 + >> mm/swap.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++ >> mm/truncate.c | 11 +++++--- >> 3 files changed, 69 insertions(+), 4 deletions(-) >> >> diff --git a/include/linux/swap.h b/include/linux/swap.h >> index eba53e7..a3c9248 100644 >> --- a/include/linux/swap.h >> +++ b/include/linux/swap.h >> @@ -213,6 +213,7 @@ 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 lru_deactive_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 3f48542..56fa298 100644 >> --- a/mm/swap.c >> +++ b/mm/swap.c >> @@ -39,6 +39,8 @@ 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_deactive_pvecs); >> + >> >> /* >> * This path almost never happens for VM activity - pages are normally >> @@ -266,6 +268,45 @@ void add_page_to_unevictable_list(struct page *page) >> spin_unlock_irq(&zone->lru_lock); >> } >> >> +static void __pagevec_lru_deactive(struct pagevec *pvec) >> +{ > > Might be worth commenting that this function must be called with pre-emption > disabled. FWIW, I am reasonably sure your implementation is prefectly safe > but a note wouldn't hurt. Will fix. > >> + int i, lru, file; >> + >> + 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); >> + } >> + >> + if (PageLRU(page)) { >> + if (PageActive(page)) { >> + 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); >> + > > What about memcg, do we not need to be calling mem_cgroup_add_lru_list() here > as well? I'm looking at the differences between what move_active_pages_to_lru() Recently, add_page_to_lru_list contains mem_cgroup_add_lru_list. > is doing and this. I'm wondering if it'd be worth your whole building a list > of active pages that are to be moved to the inactive list and passing them > to move_active_pages_to_lru() ? I confuess I have not thought about it deeply > so it might be a terrible suggestion but it might reduce duplication of code. Firstly I tried it so I sent a patch about making move_to_active_pages_to_lru more generic. move_to_active_pages_to_lru needs zone argument so I need gathering pages per zone in truncate. I don't want for user of the function to consider even zone and zone->lru_lock handling. I think the lru_demote_pages could be used elsewhere(ex, readahead max size heuristic). So it's generic and easy to use. :) > >> + update_page_reclaim_stat(zone, page, file, 0); >> + } >> + } >> + } >> + 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 >> @@ -292,8 +333,28 @@ static void drain_cpu_pagevecs(int cpu) >> pagevec_move_tail(pvec); >> local_irq_restore(flags); >> } >> + >> + pvec = &per_cpu(lru_deactive_pvecs, cpu); >> + if (pagevec_count(pvec)) >> + __pagevec_lru_deactive(pvec); >> +} >> + >> +/* >> + * Function used to forecefully demote a page to the head of the inactive >> + * list. > > s/forecefully/forcefully/ > > The comment should also state *why* and under what circumstances we move > pages to the inactive list like this. Also based on the discussions > elsewhere in this thread, it'd be nice to include a comment why it's the > head of the inactive list and not the tail. Fair enough. Thanks for the comment, Mel. -- Kind regards, Minchan Kim -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href