Memory management

Wu Fengguang | 1 May 2011 05:25

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Re: [PATCH] mmotm: fix hang at startup

On Sun, May 01, 2011 at 10:35:38AM +0800, Hugh Dickins wrote:
> Yesterday's mmotm hangs at startup, and with lockdep it reports:
> BUG: spinlock recursion on CPU#1, blkid/284 - with bdi_lock_two()
> called from bdev_inode_switch_bdi() in the backtrace.  It appears
> that this function is sometimes called with new the same as old.
>
> Signed-off-by: Hugh Dickins <hughd <at> google.com>

Thanks!

Reviewed-by: Wu Fengguang <fengguang.wu <at> intel.com>

> Fix to
> writeback-split-inode_wb_list_lock-into-bdi_writebacklist_lock.patch
> 
>  fs/block_dev.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> --- 2.6.39-rc5-mm1/fs/block_dev.c	2011-04-29 18:20:09.183314733 -0700
> +++ linux/fs/block_dev.c	2011-04-30 17:55:45.718785263 -0700
>  <at>  <at>  -57,6 +57,8  <at>  <at>  static void bdev_inode_switch_bdi(struct
>  {
>  	struct backing_dev_info *old = inode->i_data.backing_dev_info;
>  
> +	if (dst == old)
> +		return;

nitpick: it could help to add a comment

        /* avoid spinlock recursion */

(Continue reading)

KOSAKI Motohiro | 1 May 2011 08:06

Re: [PATCH 1/7] memcg: add high/low watermark to res_counter

> On Mon 25-04-11 18:28:49, KAMEZAWA Hiroyuki wrote:
> > There are two watermarks added per-memcg including "high_wmark" and "low_wmark".
> > The per-memcg kswapd is invoked when the memcg's memory usage(usage_in_bytes)
> > is higher than the low_wmark. Then the kswapd thread starts to reclaim pages
> > until the usage is lower than the high_wmark.
> 
> I have mentioned this during Ying's patchsets already, but do we really
> want to have this confusing naming? High and low watermarks have
> opposite semantic for zones.

Can you please clarify this? I feel it is not opposite semantics.

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KOSAKI Motohiro | 1 May 2011 09:27

Re: [RFC 2/8] compaction: make isolate_lru_page with filter aware

> > With the suggested flags argument from 1/8, this would look like:
> >
> >        flags = ISOLATE_BOTH;
> >        if (!cc->sync)
> >                flags |= ISOLATE_CLEAN;
> >
> > ?
> 
> Yes. I will change it.
> 
> >
> > Anyway, nice change indeed!
> 
> Thanks!

Yeah. That's very nice.
	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro <at> jp.fujitsu.com>

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KOSAKI Motohiro | 1 May 2011 15:13

Re: [RFC 4/8] Make clear description of putback_lru_page

> On Thu, Apr 28, 2011 at 08:20:32AM +0900, Minchan Kim wrote:
> > On Wed, Apr 27, 2011 at 5:11 PM, KAMEZAWA Hiroyuki
> > <kamezawa.hiroyu <at> jp.fujitsu.com> wrote:
> > > On Wed, 27 Apr 2011 01:25:21 +0900
> > > Minchan Kim <minchan.kim <at> gmail.com> wrote:
> > >
> > >> Commonly, putback_lru_page is used with isolated_lru_page.
> > >> The isolated_lru_page picks the page in middle of LRU and
> > >> putback_lru_page insert the lru in head of LRU.
> > >> It means it could make LRU churning so we have to be very careful.
> > >> Let's clear description of putback_lru_page.
> > >>
> > >> Cc: KOSAKI Motohiro <kosaki.motohiro <at> jp.fujitsu.com>
> > >> Cc: Mel Gorman <mgorman <at> suse.de>
> > >> Cc: Rik van Riel <riel <at> redhat.com>
> > >> Cc: Andrea Arcangeli <aarcange <at> redhat.com>
> > >> Signed-off-by: Minchan Kim <minchan.kim <at> gmail.com>
> > >
> > > seems good...
> > > Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu <at> jp.fujitsu.com>
> > >
> > > But is there consensus which side of LRU is tail? head?
> > 
> > I don't know. I used to think it's head.
> > If other guys raise a concern as well, let's talk about it. :)
> > Thanks
> 
> I suppose we add new pages to the head of the LRU and reclaim old
> pages from the tail.
>

(Continue reading)

KOSAKI Motohiro | 1 May 2011 15:19

Re: [RFC 5/8] compaction: remove active list counting

> On Thu, Apr 28, 2011 at 7:50 PM, Mel Gorman <mgorman <at> suse.de> wrote:
> > On Wed, Apr 27, 2011 at 01:25:22AM +0900, Minchan Kim wrote:
> >> acct_isolated of compaction uses page_lru_base_type which returns only
> >> base type of LRU list so it never returns LRU_ACTIVE_ANON or LRU_ACTIVE_FILE.
> >> So it's pointless to add lru[LRU_ACTIVE_[ANON|FILE]] to get sum.
> >>
> >> Cc: KOSAKI Motohiro <kosaki.motohiro <at> jp.fujitsu.com>
> >> Cc: Mel Gorman <mgorman <at> suse.de>
> >> Cc: Rik van Riel <riel <at> redhat.com>
> >> Cc: Andrea Arcangeli <aarcange <at> redhat.com>
> >> Signed-off-by: Minchan Kim <minchan.kim <at> gmail.com>
> >
> > hmm, isolate_migratepages() is doing a linear scan of PFNs and is
> > calling __isolate_lru_page(..ISOLATE_BOTH..). Using page_lru_base_type
> > happens to work because we're only interested in the number of isolated
> > pages and your patch still covers that. Using page_lru might be more
> > accurate in terms of accountancy but does not seem necessary.
> 
> True.
> 
> >
> > Adding a comment explaining why we account for it as inactive and why
> > that's ok would be nice although I admit this is something I should have
> > done when acct_isolated() was introduced.
> 
> When Kame pointed out comment, I wanted to avoid unnecessary comment
> so decided changing it with page_lru although it adds overhead a
> little bit. But Hannes, you and maybe Kame don't want it. I don't mind
> adding comment.
> Okay. fix it in next version.

(Continue reading)

KOSAKI Motohiro | 1 May 2011 15:47

Re: [RFC 6/8] In order putback lru core

> > +/* This structure is used for keeping LRU ordering of isolated page */
> > +struct pages_lru {
> > +        struct page *page;      /* isolated page */
> > +        struct page *prev_page; /* previous page of isolate page as LRU order */
> > +        struct page *next_page; /* next page of isolate page as LRU order */
> > +        struct list_head lru;
> > +};
> >  /*
> 
> So this thing has to be allocated from somewhere. We can't put it
> on the stack as we're already in danger there so we must be using
> kmalloc. In the reclaim paths, this should be avoided obviously.
> For compaction, we might hurt the compaction success rates if pages
> are pinned with control structures. It's something to be wary of.
> 
> At LSF/MM, I stated a preference for swapping the source and
> destination pages in the LRU. This unfortunately means that the LRU
> now contains a page in the process of being migrated to and the backout
> paths for migration failure become a lot more complex. Reclaim should
> be ok as it'll should fail to lock the page and recycle it in the list.
> This avoids allocations but I freely admit that I'm not in the position
> to implement such a thing right now :(

I like swaping to fake page. one way pointer might become dangerous. vmscan can
detect fake page and ignore it.

ie, 
is_fake_page(page)
{
	if (is_stack_addr((void*)page))

(Continue reading)

Minchan Kim | 1 May 2011 17:03

Picon

[PATCH 0/2] Fix an enhance deactive_page

A few days ago, Ying reported a problem.
http://marc.info/?l=linux-mm&m=130403310601663&w=2
After I and Ying dive in problem, We found deactive_page
has a problem. Apparently, It's a BUG so 
[1/2] is fix of the problem and [2/2] is enhancement for 
helping CPU.

Minchan Kim (2):
  [1/2] Check PageUnevictable in lru_deactivate_fn
  [2/2] Filter unevictable page out in deactivate_page

 mm/swap.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

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Minchan Kim | 1 May 2011 17:03

Picon

[PATCH 1/2] Check PageUnevictable in lru_deactivate_fn

The lru_deactivate_fn should not move page which in on unevictable lru
into inactive list. Otherwise, we can meet BUG when we use isolate_lru_pages
as __isolate_lru_page could return -EINVAL.
It's really BUG and let's fix it.

Reported-by: Ying Han <yinghan <at> google.com>
Tested-by: Ying Han <yinghan <at> google.com>
Signed-off-by: Minchan Kim <minchan.kim <at> gmail.com>
---
 mm/swap.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/mm/swap.c b/mm/swap.c
index a83ec5a..2e9656d 100644
--- a/mm/swap.c
+++ b/mm/swap.c
 <at>  <at>  -429,6 +429,9  <at>  <at>  static void lru_deactivate_fn(struct page *page, void *arg)
 	if (!PageLRU(page))
 		return;

+	if (PageUnevictable(page))
+		return;
+
 	/* Some processes are using the page */
 	if (page_mapped(page))
 		return;
--

-- 
1.7.1

--

(Continue reading)

Minchan Kim | 1 May 2011 17:03

Picon

[PATCH 2/2] Filter unevictable page out in deactivate_page

It's pointless that deactive_page's pagevec operation about
unevictable page as it's nop.
This patch removes unnecessary overhead which might be a bit problem
in case that there are many unevictable page in system(ex, mprotect workload)

Signed-off-by: Minchan Kim <minchan.kim <at> gmail.com>
---
 mm/swap.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/mm/swap.c b/mm/swap.c
index 2e9656d..b707694 100644
--- a/mm/swap.c
+++ b/mm/swap.c
 <at>  <at>  -511,6 +511,15  <at>  <at>  static void drain_cpu_pagevecs(int cpu)
  */
 void deactivate_page(struct page *page)
 {
+
+	/*
+	 * In workload which system has many unevictable page(ex, mprotect),
+	 * unevictalge page deactivation for accelerating reclaim
+	 * is pointless.
+	 */
+	if (PageUnevictable(page))
+		return;
+
 	if (likely(get_page_unless_zero(page))) {
 		struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);

(Continue reading)

Minchan Kim | 1 May 2011 17:09

Picon

Re: [RFC 5/8] compaction: remove active list counting

On Sun, May 1, 2011 at 10:19 PM, KOSAKI Motohiro
<kosaki.motohiro <at> jp.fujitsu.com> wrote:
>> On Thu, Apr 28, 2011 at 7:50 PM, Mel Gorman <mgorman <at> suse.de> wrote:
>> > On Wed, Apr 27, 2011 at 01:25:22AM +0900, Minchan Kim wrote:
>> >> acct_isolated of compaction uses page_lru_base_type which returns only
>> >> base type of LRU list so it never returns LRU_ACTIVE_ANON or LRU_ACTIVE_FILE.
>> >> So it's pointless to add lru[LRU_ACTIVE_[ANON|FILE]] to get sum.
>> >>
>> >> Cc: KOSAKI Motohiro <kosaki.motohiro <at> jp.fujitsu.com>
>> >> Cc: Mel Gorman <mgorman <at> suse.de>
>> >> Cc: Rik van Riel <riel <at> redhat.com>
>> >> Cc: Andrea Arcangeli <aarcange <at> redhat.com>
>> >> Signed-off-by: Minchan Kim <minchan.kim <at> gmail.com>
>> >
>> > hmm, isolate_migratepages() is doing a linear scan of PFNs and is
>> > calling __isolate_lru_page(..ISOLATE_BOTH..). Using page_lru_base_type
>> > happens to work because we're only interested in the number of isolated
>> > pages and your patch still covers that. Using page_lru might be more
>> > accurate in terms of accountancy but does not seem necessary.
>>
>> True.
>>
>> >
>> > Adding a comment explaining why we account for it as inactive and why
>> > that's ok would be nice although I admit this is something I should have
>> > done when acct_isolated() was introduced.
>>
>> When Kame pointed out comment, I wanted to avoid unnecessary comment
>> so decided changing it with page_lru although it adds overhead a
>> little bit. But Hannes, you and maybe Kame don't want it. I don't mind

(Continue reading)

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[PATCH] mm: Fix warning (22 May 2013)
[PATCH 1/4] mm/memory-hotplug: fix lowmem count overflow when offline (22 May 2013)
[PATCH v7 0/8] kdump, vmcore: support mmap() on /proc/vmcore (22 May 2013)
[PATCH] mm: Change normal message to use pr_debug (21 May 2013)
[PATCH v2] mm: vmscan: add VM_BUG_ON on illegal return values from sca (21 May 2013)
[RFC PATCH] zswap: add zswap shrinker (21 May 2013)
[RFC PATCH 00/02] swap: allowing a more flexible DISCARD policy (21 May 2013)
[PATCHv12 0/4] zswap: compressed swap caching (20 May 2013)
Bye bye Mr tmem guy (20 May 2013)
[PATCH] staging: ramster: add how-to document (20 May 2013)
[PATCH] mm: vmscan: add BUG_ON on illegal return values from scan_obje (20 May 2013)
[Suggestion] mm/bootmem.c: need return failure code when BUG() neithe (20 May 2013)
[PATCH 0/5] ACPI / scan / memhotplug: ACPI hotplug rework followup cha (19 May 2013)
[PATCH] mm/memory-failure.c: fix memory leak in successful soft offlin (17 May 2013)
readahead man page incorrectly says it blocks (17 May 2013)
[PATCH] mm/nommu.c: add additional check for vread() just like vwrite( (17 May 2013)
[PATCH] mm/page_alloc.c: add additional checking and return value for (17 May 2013)
[PATCH 0/5] Obey mark_page_accessed hint given by filesystems v3r1 (17 May 2013)
[patch v3 -mm 1/3] memcg: integrate soft reclaim tighter with zone shr (17 May 2013)
[PATCH 0/12][V3] memcg: make memcg's life cycle the same as cgroup (17 May 2013)
[PATCH] memcg: update TODO list in Documentation (17 May 2013)

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