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Message-ID: <AANLkTi=Pko=HKkhT7cPxxc+d7weiFi0ur66q-W-LiA+d@mail.gmail.com>
Date: Fri, 18 Feb 2011 19:39:27 +0900
From: Minchan Kim <minchan.kim@...il.com>
To: balbir@...ux.vnet.ibm.com
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-mm <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
Steven Barrett <damentz@...uorix.net>,
Ben Gamari <bgamari.foss@...il.com>,
Peter Zijlstra <peterz@...radead.org>,
Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Wu Fengguang <fengguang.wu@...el.com>,
Johannes Weiner <hannes@...xchg.org>,
Nick Piggin <npiggin@...nel.dk>,
Andrea Arcangeli <aarcange@...hat.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH v5 1/4] deactivate invalidated pages
Hi Balbir,
On Fri, Feb 18, 2011 at 3:29 PM, Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> * MinChan Kim <minchan.kim@...il.com> [2011-02-18 00:08:19]:
>
>> 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@...il.com>
>> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
>> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
>> Acked-by: Rik van Riel <riel@...hat.com>
>> Acked-by: Mel Gorman <mel@....ul.ie>
>> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>> Cc: Wu Fengguang <fengguang.wu@...el.com>
>> Cc: Johannes Weiner <hannes@...xchg.org>
>> Cc: Nick Piggin <npiggin@...nel.dk>
>> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
>> ---
>> 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);
>> + }
>
> The optimization to avoid taking locks if the zone does not change is
> quite subtle
I just used it without big considering as it's a normal technique of
page array handling we have been used. So I want to keep it if it
doesn't make big overhead.
>
>> + 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);
>
> Do we need to do this under page_lock? Is there scope for us to reuse
> rotate_reclaimable_page() logic?
Good point.
I think we don't need page_lock. will fix.
About rotate_reclaimable_page, it has little bit similar logic but
several page flags test and irq disable are different so it would
result in ugly shape as far as I think.
I hope if you have a good idea, please, do refactoring after merging.
Thanks for the review, Balbir.
--
Kind regards,
Minchan Kim
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