OOM kills if swappiness set to 0, swap storms otherwise

OOM kills if swappiness set to 0, swap storms otherwise

[Lee Revell]

I am simply trying to run a Gnome desktop (Gnome 2.14, Evolution,
Firefox, gtk-gnutella usually open) without swapping or getting OOM
killed.

I have to set the swappiness to 0 or else I get swap storms when simply
browsing the web and reading my mail.  I think this is insane as I have
512MB of RAM.  It seems as if the kernel will OOM kill firefox rather
than shrink the file cache!

What is the problem here?  Is the modern Linux desktop really too
bloated to run in half a gig of RAM, or is the kernel overzealous with
its OOM killing?

Lee

oom-killer: gfp_mask=0x280d2, order=0
Mem-info:
DMA per-cpu:
cpu 0 hot: high 0, batch 1 used:0
cpu 0 cold: high 0, batch 1 used:0
DMA32 per-cpu: empty
Normal per-cpu:
cpu 0 hot: high 186, batch 31 used:23
cpu 0 cold: high 62, batch 15 used:46
HighMem per-cpu: empty
Free pages:        4476kB (0kB HighMem)
Active:84715 inactive:9418 dirty:0 writeback:0 unstable:0 free:1119
slab:4615 mapped:93948 pagetables:662
DMA free:1252kB min:96kB low:120kB high:144kB active:0kB inactive:0kB
present:16384kB pages_scanned:10238 all_unreclaimable? yes
lowmem_reserve[]: 0 0 431 431
DMA32 free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB
present:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 431 431
Normal free:3224kB min:2608kB low:3260kB high:3912kB active:338860kB
inactive:37672kB present:442304kB pages_scanned:61895 all_unreclaim
able? no
lowmem_reserve[]: 0 0 0 0
HighMem free:0kB min:128kB low:128kB high:128kB active:0kB inactive:0kB
present:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 0 0
DMA: 3*4kB 3*8kB 2*16kB 1*32kB 2*64kB 2*128kB 1*256kB 1*512kB 0*1024kB
0*2048kB 0*4096kB = 1252kB
DMA32: empty
Normal: 174*4kB 28*8kB 0*16kB 2*32kB 1*64kB 1*128kB 0*256kB 0*512kB
0*1024kB 1*2048kB 0*4096kB = 3224kB
HighMem: empty
Swap cache: add 635780, delete 617326, find 164667/241301, race 0+0
Free swap  = 315164kB
Total swap = 499928kB
Free swap:       315164kB
114672 pages of RAM
0 pages of HIGHMEM
5150 reserved pages
41086 pages shared
18438 pages swap cached
0 pages dirty
0 pages writeback
93765 pages mapped
4615 pages slab
662 pages pagetables
Out of Memory: Killed process 32663 (firefox-bin).

rlrevell@mindpipe:~$ vmstat 1
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 2  0 248992   5612   4072  75268    3    2    41    49   12    33 82  4 14  1
 0  0 248992   5364   4084  75300    0    0     0   128 1273   640 34  3 63  0
 0  0 248992   5356   4084  75464    0    0     0     0 1257   611 23  4 73  0
 0  0 248992   5356   4084  75496    0    0     0     0 1292   635 21  2 77  0
 0  0 248992   5356   4084  75532    0    0     0     0 1277   599 22  3 75  0
 0  0 248992   5356   4084  75532    0    0     0     0 1270   610 23  2 75  0
 1  0 248992   5232   4092  75564    0    0     0   200 1274   596 21  2 77  0
 0  0 248992   5232   4092  75564    0    0     0     0 1280   648 22  2 76  0
 0  0 248992   5108   4092  75696    0    0     0     0 1296   621 21  4 75  0

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
rlrevell  1792  4.1 37.9 320340 166724 ?       Sl   Mar21 353:33 evolution --component=mail
rlrevell  2298  9.2 18.9 200556 83112 ?        Sl   15:16  30:55 /usr/lib/firefox/firefox-bin -a firefox
rlrevell  1794  0.0  2.1  92704  9344 ?        Sl   Mar21   0:47 /usr/lib/evolution/evolution-data-server-1.6 --oaf-activate-iid=OAFIID:GNOME_Evolution_DataServer_InterfaceCheck --oaf-ior-fd=41
pdnsd    10545  0.0  0.1  75676   600 ?        Sl   18:55   0:00 /usr/sbin/pdnsd --daemon -p /var/run/pdnsd.pid
rlrevell  1805  0.0  0.6  65236  2740 ?        Sl   Mar21   0:06 /usr/lib/evolution/2.6/evolution-alarm-notify --oaf-activate-iid=OAFIID:GNOME_Evolution_Calendar_AlarmNotify_Factory:2.6 --oaf-ior-fd=43
root      2295 70.3  4.5  58160 19908 tty7     Ss+  Mar18 9207:34 /usr/bin/X :0 -br -audit 0 -auth /var/lib/gdm/:0.Xauth -nolisten tcp vt7
rlrevell  2759  0.0  1.0  57716  4832 ?        Ssl  Mar18   2:48 nautilus --sm-config-prefix /nautilus-kFkhxG/ --sm-client-id 106281f446000113283283500000043730002 --screen 0 --no-default-window
rlrevell  2749  0.0  0.5  33720  2404 ?        Sl   Mar18   3:09 /usr/lib/control-center/gnome-settings-daemon --oaf-activate-iid=OAFIID:GNOME_SettingsDaemon --oaf-ior-fd=25
rlrevell 11452 17.2  3.9  31828 17348 ?        S    20:15   5:49 gtk-gnutella
rlrevell  2934  0.1  1.7  28736  7548 ?        Sl   Mar18  20:09 /usr/lib/gnome-panel/wnck-applet --oaf-activate-iid=OAFIID:GNOME_Wncklet_Factory --oaf-ior-fd=33
rlrevell 11751  0.0  0.1  27180   524 pts/0    S+   20:49   0:00 sort -k5 -rn
rlrevell  2757  0.0  1.8  24220  8148 ?        Ssl  Mar18   5:54 gnome-panel --sm-config-prefix /gnome-panel-daqxPK/ --sm-client-id 106281f446000113283283400000043730001 --screen 0
rlrevell  2785  0.0  0.7  20784  3400 ?        S    Mar18   1:10 /usr/lib/gnome-panel/clock-applet --oaf-activate-iid=OAFIID:GNOME_ClockApplet_Factory --oaf-ior-fd=35
rlrevell  2669  0.0  0.6  17212  2704 ?        Ss   Mar18   0:22 x-session-manager
rlrevell  2783  0.0  0.5  15288  2328 ?        S    Mar18   0:17 /usr/lib/gnome-panel/notification-area-applet --oaf-activate-iid=OAFIID:GNOME_NotificationAreaApplet_Factory --oaf-ior-fd=34
rlrevell 11453  0.0  0.1  14088   480 ?        S    20:15   0:00 DNS helper for gtk-gnutella
rlrevell  2860  0.0  0.5  13732  2512 ?        Ss   Mar18   2:29 gnome-screensaver
rlrevell  2755  0.1  1.1  13484  5216 ?        Ss   Mar18  13:17 metacity --sm-save-file 1132974963-4486-1014928945.ms
root      2291  0.0  0.0  10148   388 ?        S    Mar18   0:04 /usr/sbin/gdm
root      2286  0.0  0.0   9668   256 ?        Ss   Mar18   0:00 /usr/sbin/gdm

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Andrew Morton]

Lee Revell <rlrevell@joe-job.com> wrote:
>
> I am simply trying to run a Gnome desktop (Gnome 2.14, Evolution,
> Firefox, gtk-gnutella usually open) without swapping or getting OOM
> killed.
> 
> I have to set the swappiness to 0 or else I get swap storms when simply
> browsing the web and reading my mail.  I think this is insane as I have
> 512MB of RAM.  It seems as if the kernel will OOM kill firefox rather
> than shrink the file cache!

No, there is little pagecache left.

> What is the problem here?  Is the modern Linux desktop really too
> bloated to run in half a gig of RAM, or is the kernel overzealous with
> its OOM killing?

Looks like it.

> ...
> 
> rlrevell@mindpipe:~$ vmstat 1
> procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
>  2  0 248992   5612   4072  75268    3    2    41    49   12    33 82  4 14  1
>  0  0 248992   5364   4084  75300    0    0     0   128 1273   640 34  3 63  0
>  0  0 248992   5356   4084  75464    0    0     0     0 1257   611 23  4 73  0
>  0  0 248992   5356   4084  75496    0    0     0     0 1292   635 21  2 77  0
>  0  0 248992   5356   4084  75532    0    0     0     0 1277   599 22  3 75  0
>  0  0 248992   5356   4084  75532    0    0     0     0 1270   610 23  2 75  0
>  1  0 248992   5232   4092  75564    0    0     0   200 1274   596 21  2 77  0
>  0  0 248992   5232   4092  75564    0    0     0     0 1280   648 22  2 76  0
>  0  0 248992   5108   4092  75696    0    0     0     0 1296   621 21  4 75  0

70-odd MB in pagecache.  Probably a lot of this is mmapped into process
pagetables and by setting swappiness==0 you've basically told the kernel
that this memory is to be preserved.

> rlrevell  1792  4.1 37.9 320340 166724 ?       Sl   Mar21 353:33 evolution --component=mail
> rlrevell  2298  9.2 18.9 200556 83112 ?        Sl   15:16  30:55 /usr/lib/firefox/firefox-bin -a firefox
> rlrevell  1794  0.0  2.1  92704  9344 ?        Sl   Mar21   0:47 /usr/lib/evolution/evolution-data-server-1.6 --oaf-activate-iid=OAFIID:GNOME_Evolution_DataServer_InterfaceCheck --oaf-ior-fd=41
> rlrevell  1805  0.0  0.6  65236  2740 ?        Sl   Mar21   0:06 /usr/lib/evolution/2.6/evolution-alarm-notify --oaf-activate-iid=OAFIID:GNOME_Evolution_Calendar_AlarmNotify_Factory:2.6 --oaf-ior-fd=43
> root      2295 70.3  4.5  58160 19908 tty7     Ss+  Mar18 9207:34 /usr/bin/X :0 -br -audit 0 -auth /var/lib/gdm/:0.Xauth -nolisten tcp vt7
> rlrevell  2759  0.0  1.0  57716  4832 ?        Ssl  Mar18   2:48 nautilus --sm-config-prefix /nautilus-kFkhxG/ --sm-client-id 106281f446000113283283500000043730002 --screen 0 --no-default-window
> rlrevell  2749  0.0  0.5  33720  2404 ?        Sl   Mar18   3:09 /usr/lib/control-center/gnome-settings-daemon --oaf-activate-iid=OAFIID:GNOME_SettingsDaemon --oaf-ior-fd=25

Much porkiness.

/proc/meminfo is very useful for obtaining a top-level view of where all
the memory's gone to.  I'd tentatively say that your options are to put up
with the swapping or find a new mail client.

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Lee Revell]

On Mon, 2006-03-27 at 19:59 -0800, Andrew Morton wrote:
> Much porkiness.
> 
> /proc/meminfo is very useful for obtaining a top-level view of where all
> the memory's gone to.  I'd tentatively say that your options are to put up
> with the swapping or find a new mail client.
> 

Thanks.  It seems the problem is Evo (or possibly firefox) has a slow
memory leak.  I overlooked the fact that Evo had been running for more
than a week.

I guess the only possible kernel issue is that Evo never gets
OOM-killed, always Firefox (or OpenOffice if it's running), although
it's the biggest hog.  I'll have to investigate more.

Lee

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Parag Warudkar]

On Monday 27 March 2006 22:59, Andrew Morton wrote:
> I'd tentatively say that your options are to put up
> with the swapping or find a new mail client.

I tried mem=512m , swapoff -a and swappiness=0 and all works fine for me on 
x86. I use Evolution and Firefox's KDE counterparts - in addition to that 
Amarok, Kopete and Akregator fit in too.

Lee - Perhaps you are running fat 64 bit code?

Parag

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Lee Revell]

On Mon, 2006-03-27 at 23:12 -0500, Parag Warudkar wrote:
> Lee - Perhaps you are running fat 64 bit code?

Nope, 32 bit system.  I think the problem is just a boring old memory
leak.

Lee

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Alan Cox]

On Llu, 2006-03-27 at 20:53 -0500, Lee Revell wrote:
> What is the problem here?  Is the modern Linux desktop really too
> bloated to run in half a gig of RAM, or is the kernel overzealous with
> its OOM killing?

Evolution will regularly try and eat over 1GByte of RAM. In addition it
is possible for an attacker to send you a plain text email that makes it
do this.

If you want to run gnome & firefox & evolution you need a lot more RAM.
Alternatively run something sane and sensible.

Alan
(whose todo list does indeed have 'new mailer' on it)

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Charles Shannon Hendrix]

Mon, 27 Mar 2006 @ 19:59 -0800, Andrew Morton said:

> Much porkiness.
> 
> /proc/meminfo is very useful for obtaining a top-level view of where all
> the memory's gone to.  I'd tentatively say that your options are to put up
> with the swapping or find a new mail client.

I use mutt for my email, and I have the same issue on a 1GB system.

I really wish we could put an upper limit on what file cache can use.

I understand the original poster was running a lot of pork, but you
don't have to and still see a problem with swapping.  Even running KDE
my total application memory most of the time is 300MB or less on a
machine with 1GB of memory.

I shouldn't be suffering from swap storms.

For example, my normal working set of programs eats about 250MB of memory. If
I also start a job running to something like tag some mp3s, copy a CD, or just
process a lot of files, it only takes a few minutes before performance becomes
unacceptable.  

If you are doing some work where you switch among several applications
frequently, the pigginess of file cache becomes a serious problem.

Isn't that bad behavior by any measure?



-- 
shannon "AT" widomaker.com -- ["It's a damn poor mind that can only think
of one way to spell a word." -- Andrew Jackson]

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Bill Davidsen]

Charles Shannon Hendrix wrote:
> Mon, 27 Mar 2006 @ 19:59 -0800, Andrew Morton said:
> 
>> Much porkiness.
>>
>> /proc/meminfo is very useful for obtaining a top-level view of where all
>> the memory's gone to.  I'd tentatively say that your options are to put up
>> with the swapping or find a new mail client.
> 
> I use mutt for my email, and I have the same issue on a 1GB system.
> 
> I really wish we could put an upper limit on what file cache can use.
> 
> I understand the original poster was running a lot of pork, but you
> don't have to and still see a problem with swapping.  Even running KDE
> my total application memory most of the time is 300MB or less on a
> machine with 1GB of memory.
> 
> I shouldn't be suffering from swap storms.

Agreed, does meminfo show that you are? The reason I ask is that I have 
noted that large memory machines and CD/DVD image writing suffer from 
some interesting disk write patterns. The image being built gets cached 
but not written, then the file is closed. At some point the kernel 
notices several GB of old unwritten data and decides to write it. This 
makes everything pretty slow for a while, even if you have 100MB/s disk 
system.
> 
> For example, my normal working set of programs eats about 250MB of memory. If
> I also start a job running to something like tag some mp3s, copy a CD, or just
> process a lot of files, it only takes a few minutes before performance becomes
> unacceptable.  

In theory you should be able to tune this, but in practice I see what 
you do. On small memory machines it's less noticable, oddly.
> 
> If you are doing some work where you switch among several applications
> frequently, the pigginess of file cache becomes a serious problem.
> 
> Isn't that bad behavior by any measure?

-- 
    -bill davidsen (davidsen@tmr.com)
"The secret to procrastination is to put things off until the
  last possible moment - but no longer"  -me

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Shantanu Goel]

[-- Attachment #1: Type: text/plain, Size: 1590 bytes --]

Charles,

Can you please try the attached patch against 2.6.16.1
which I use on my desktop since I encountered the same
issues when running GNOME/Firefox etc.  After booting
the patched kernel, leave swappiness unchanged but do
the following:

  echo 1 > /proc/sys/vm/mapped_bias

This should allow mapped memory to stay pretty close
to 80% as implied by the default swappiness value of
60 and prevent the swap storms.

Andrew et al, details on the patch are as follows.

1. Unmapped pages are kept the inactive list as much
as possible.

2. Only partially written pages are marked as
referenced so kswapd can initiate writeback on the
first scan for sequentially written files.

3. The scanner will set PG_reclaim for pages found in
writeback.

4. The scanner will scan the LRU twice.  On the first
pass, the distress logic is disabled while on the
second pass, it is applied as before.  This permits a
full scan of the inactive list before distress
swapping begins.

5. The slab scanner only takes into account the size
of the inactive list and scans the slab at 1/2 the
rate of the inactive list for DEFAULT_SEEKS.  This
prevents spurious pageouts during heavy slab usage
such as when running updatedb.

6. reclaim_mapped is made part of scan_control so it
can be used by shrink_list() in addition to
refill_inactive_zone() to prevent mapped memory
reclamation and staying within the bounds dictated by
swappiness.

Thanks,
Shantanu

__________________________________________________
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[-- Attachment #2: 2495889862-01-mapped-bias.patch --]
[-- Type: application/octet-stream, Size: 14057 bytes --]

--- .orig/include/linux/swap.h	2006-04-05 20:29:09.000000000 -0400
+++ 01-mapped-bias/include/linux/swap.h	2006-04-03 19:25:15.000000000 -0400
@@ -175,6 +175,7 @@
 extern int try_to_free_pages(struct zone **, gfp_t);
 extern int shrink_all_memory(int);
 extern int vm_swappiness;
+extern int vm_mapped_bias;
 
 #ifdef CONFIG_NUMA
 extern int zone_reclaim_mode;
--- .orig/include/linux/sysctl.h	2006-04-05 20:29:09.000000000 -0400
+++ 01-mapped-bias/include/linux/sysctl.h	2006-04-03 19:25:04.000000000 -0400
@@ -186,6 +186,7 @@
 	VM_PERCPU_PAGELIST_FRACTION=30,/* int: fraction of pages in each percpu_pagelist */
 	VM_ZONE_RECLAIM_MODE=31, /* reclaim local zone memory before going off node */
 	VM_ZONE_RECLAIM_INTERVAL=32, /* time period to wait after reclaim failure */
+	VM_MAPPED_BIAS=33,	/* bias reclaim towards preserving mapped memory */
 };
 
 
--- .orig/kernel/sysctl.c	2006-04-05 20:29:09.000000000 -0400
+++ 01-mapped-bias/kernel/sysctl.c	2006-04-03 19:40:49.000000000 -0400
@@ -916,6 +916,16 @@
 		.strategy	= &sysctl_jiffies,
 	},
 #endif
+	{
+		.ctl_name	= VM_MAPPED_BIAS,
+		.procname	= "mapped_bias",
+		.data		= &vm_mapped_bias,
+		.maxlen		= sizeof(vm_mapped_bias),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &zero,
+	},
 	{ .ctl_name = 0 }
 };
 
--- .orig/mm/filemap.c	2006-04-05 20:29:09.000000000 -0400
+++ 01-mapped-bias/mm/filemap.c	2006-04-03 19:31:07.000000000 -0400
@@ -2020,7 +2020,14 @@
 			if (status >= 0)
 				status = -EFAULT;
 		unlock_page(page);
-		mark_page_accessed(page);
+
+		/*
+		 * Only mark page accessed for partial write
+		 * when mapped bias is in effect.
+		 */
+		if (!vm_mapped_bias || offset + bytes != PAGE_CACHE_SIZE)
+			mark_page_accessed(page);
+
 		page_cache_release(page);
 		if (status < 0)
 			break;
--- .orig/mm/page_alloc.c	2006-04-05 20:29:10.000000000 -0400
+++ 01-mapped-bias/mm/page_alloc.c	2006-04-03 20:00:22.000000000 -0400
@@ -360,7 +360,6 @@
 			1 << PG_private |
 			1 << PG_locked	|
 			1 << PG_active	|
-			1 << PG_reclaim	|
 			1 << PG_slab	|
 			1 << PG_swapcache |
 			1 << PG_writeback |
@@ -518,7 +517,6 @@
 			1 << PG_locked	|
 			1 << PG_active	|
 			1 << PG_dirty	|
-			1 << PG_reclaim	|
 			1 << PG_slab    |
 			1 << PG_swapcache |
 			1 << PG_writeback |
@@ -534,7 +532,8 @@
 
 	page->flags &= ~(1 << PG_uptodate | 1 << PG_error |
 			1 << PG_referenced | 1 << PG_arch_1 |
-			1 << PG_checked | 1 << PG_mappedtodisk);
+			1 << PG_checked | 1 << PG_mappedtodisk |
+			1 << PG_reclaim);
 	set_page_private(page, 0);
 	set_page_refs(page, order);
 	kernel_map_pages(page, 1 << order, 1);
--- .orig/mm/swap.c	2006-04-05 20:29:10.000000000 -0400
+++ 01-mapped-bias/mm/swap.c	2006-04-03 19:28:55.000000000 -0400
@@ -103,12 +103,23 @@
 {
 	struct zone *zone = page_zone(page);
 
+	if (unlikely(PageReclaim(page)))
+		ClearPageReclaim(page);
+
 	spin_lock_irq(&zone->lru_lock);
 	if (PageLRU(page) && !PageActive(page)) {
-		del_page_from_inactive_list(zone, page);
-		SetPageActive(page);
-		add_page_to_active_list(zone, page);
-		inc_page_state(pgactivate);
+		/*
+		 * Never activate an unmapped page when
+		 * mapped bias is in effect.
+		 */
+		if (!vm_mapped_bias || page_mapped(page)) {
+			del_page_from_inactive_list(zone, page);
+			SetPageActive(page);
+			add_page_to_active_list(zone, page);
+			inc_page_state(pgactivate);
+		} else if (page->lru.prev != &zone->inactive_list) {
+			list_move(&page->lru, &zone->inactive_list);
+		}
 	}
 	spin_unlock_irq(&zone->lru_lock);
 }
@@ -127,6 +138,8 @@
 		ClearPageReferenced(page);
 	} else if (!PageReferenced(page)) {
 		SetPageReferenced(page);
+		if (PageReclaim(page))
+			ClearPageReclaim(page);
 	}
 }
 
--- .orig/mm/vmscan.c	2006-04-05 20:29:10.000000000 -0400
+++ 01-mapped-bias/mm/vmscan.c	2006-04-03 20:08:36.000000000 -0400
@@ -79,6 +79,12 @@
 	 * In this context, it doesn't matter that we scan the
 	 * whole list at once. */
 	int swap_cluster_max;
+
+	/* Should we reclaim mapped memory? */
+	int reclaim_mapped;
+
+	/* LRU pass */
+	int pass;
 };
 
 /*
@@ -128,6 +134,30 @@
 int vm_swappiness = 60;
 static long total_memory;
 
+/*
+ * When non-zero, place all unmapped pages on
+ * the inactive list and do not reclaim any mapped
+ * pages unless mapped memory exceeds the threshold
+ * implied by swappiness above.
+ */
+int vm_mapped_bias = 0;
+static int mapped_bias = 0;
+static atomic_t scanner_running = ATOMIC_INIT(-1);
+
+static inline void scanner_start(void)
+{
+	/*
+	 * Re-sync mapped bias on first run.
+	 */
+	if (atomic_inc_and_test(&scanner_running))
+		mapped_bias = vm_mapped_bias;
+}
+
+static inline void scanner_stop(void)
+{
+	atomic_dec(&scanner_running);
+}
+
 static LIST_HEAD(shrinker_list);
 static DECLARE_RWSEM(shrinker_rwsem);
 
@@ -199,7 +229,17 @@
 		unsigned long total_scan;
 		unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask);
 
-		delta = (4 * scanned) / shrinker->seeks;
+		/*
+		 * With mapped bias in effect, we only count
+		 * inactive pages as part of lru_pages causing
+		 * the default algorithm to be quite aggressive.
+		 * To remedy that, we scan the slabs at a fraction
+		 * of the LRU scan rate.
+		 */
+		if (!mapped_bias)
+			delta = (4 * scanned) / shrinker->seeks;
+		else
+			delta = scanned / shrinker->seeks;
 		delta *= max_pass;
 		do_div(delta, lru_pages + 1);
 		shrinker->nr += delta;
@@ -444,15 +484,28 @@
 
 		sc->nr_scanned++;
 
+		/*
+		 * Do not reclaim a mapped page unless
+		 * necessary when mapped bias is in effect.
+		 */
+		if (mapped_bias && !sc->reclaim_mapped && page_mapped(page))
+			goto do_activate_locked;
+
 		if (!sc->may_swap && page_mapped(page))
 			goto keep_locked;
 
 		/* Double the slab pressure for mapped and swapcache pages */
-		if (page_mapped(page) || PageSwapCache(page))
+		if (!mapped_bias && (page_mapped(page) || PageSwapCache(page)))
 			sc->nr_scanned++;
 
-		if (PageWriteback(page))
+		if (PageWriteback(page)) {
+			/*
+			 * Set reclaim bit when mapped bias is in effect.
+			 */
+			if (mapped_bias)
+				SetPageReclaim(page);
 			goto keep_locked;
+		}
 
 		referenced = page_referenced(page, 1);
 		/* In active use or really unfreeable?  Activate it. */
@@ -567,8 +620,15 @@
 		continue;
 
 activate_locked:
-		SetPageActive(page);
-		pgactivate++;
+		/*
+		 * Do not activate an unmapped page if
+		 * mapped bias is in effect.
+		 */
+		if (!mapped_bias || page_mapped(page)) {
+do_activate_locked:
+			SetPageActive(page);
+			pgactivate++;
+		}
 keep_locked:
 		unlock_page(page);
 keep:
@@ -1200,48 +1260,6 @@
 	LIST_HEAD(l_active);	/* Pages to go onto the active_list */
 	struct page *page;
 	struct pagevec pvec;
-	int reclaim_mapped = 0;
-
-	if (unlikely(sc->may_swap)) {
-		long mapped_ratio;
-		long distress;
-		long swap_tendency;
-
-		/*
-		 * `distress' is a measure of how much trouble we're having
-		 * reclaiming pages.  0 -> no problems.  100 -> great trouble.
-		 */
-		distress = 100 >> zone->prev_priority;
-
-		/*
-		 * The point of this algorithm is to decide when to start
-		 * reclaiming mapped memory instead of just pagecache.  Work out
-		 * how much memory
-		 * is mapped.
-		 */
-		mapped_ratio = (sc->nr_mapped * 100) / total_memory;
-
-		/*
-		 * Now decide how much we really want to unmap some pages.  The
-		 * mapped ratio is downgraded - just because there's a lot of
-		 * mapped memory doesn't necessarily mean that page reclaim
-		 * isn't succeeding.
-		 *
-		 * The distress ratio is important - we don't want to start
-		 * going oom.
-		 *
-		 * A 100% value of vm_swappiness overrides this algorithm
-		 * altogether.
-		 */
-		swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
-
-		/*
-		 * Now use this metric to decide whether to start moving mapped
-		 * memory onto the inactive list.
-		 */
-		if (swap_tendency >= 100)
-			reclaim_mapped = 1;
-	}
 
 	lru_add_drain();
 	spin_lock_irq(&zone->lru_lock);
@@ -1256,7 +1274,7 @@
 		page = lru_to_page(&l_hold);
 		list_del(&page->lru);
 		if (page_mapped(page)) {
-			if (!reclaim_mapped ||
+			if (!sc->reclaim_mapped ||
 			    (total_swap_pages == 0 && PageAnon(page)) ||
 			    page_referenced(page, 0)) {
 				list_add(&page->lru, &l_active);
@@ -1333,6 +1351,51 @@
 	unsigned long nr_active;
 	unsigned long nr_inactive;
 
+	sc->reclaim_mapped = 0;
+	if (unlikely(sc->may_swap)) {
+		long mapped_ratio;
+		long distress;
+		long swap_tendency;
+
+		/*
+		 * `distress' is a measure of how much trouble we're having
+		 * reclaiming pages.  0 -> no problems.  100 -> great trouble.
+		 *
+		 * When mapped bias is in effect, only apply distress in the
+		 * last pass.
+		 */
+		distress = (sc->pass == 0) ? 100 >> zone->prev_priority : 0;
+
+		/*
+		 * The point of this algorithm is to decide when to start
+		 * reclaiming mapped memory instead of just pagecache.  Work out
+		 * how much memory
+		 * is mapped.
+		 */
+		mapped_ratio = (sc->nr_mapped * 100) / total_memory;
+
+		/*
+		 * Now decide how much we really want to unmap some pages.  The
+		 * mapped ratio is downgraded - just because there's a lot of
+		 * mapped memory doesn't necessarily mean that page reclaim
+		 * isn't succeeding.
+		 *
+		 * The distress ratio is important - we don't want to start
+		 * going oom.
+		 *
+		 * A 100% value of vm_swappiness overrides this algorithm
+		 * altogether.
+		 */
+		swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
+
+		/*
+		 * Now use this metric to decide whether to start moving mapped
+		 * memory onto the inactive list.
+		 */
+		if (swap_tendency >= 100)
+			sc->reclaim_mapped = 1;
+	}
+
 	atomic_inc(&zone->reclaim_in_progress);
 
 	/*
@@ -1437,10 +1500,14 @@
 	struct scan_control sc;
 	unsigned long lru_pages = 0;
 	int i;
+	int max_priority;
+
+	scanner_start();
 
 	sc.gfp_mask = gfp_mask;
 	sc.may_writepage = !laptop_mode;
 	sc.may_swap = 1;
+	sc.pass = !!mapped_bias;
 
 	inc_page_state(allocstall);
 
@@ -1451,10 +1518,22 @@
 			continue;
 
 		zone->temp_priority = DEF_PRIORITY;
-		lru_pages += zone->nr_active + zone->nr_inactive;
+
+		/*
+		 * When mapped bias is in effect,
+		 * do not count active pages.
+		 */
+		lru_pages += zone->nr_inactive;
+		if (!mapped_bias)
+			lru_pages += zone->nr_active;
 	}
+again:
+	/*
+	 * Only scan down to 0 on the last pass.
+	 */
+	max_priority = (sc.pass == 0) ? 0 : 1;
 
-	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
+	for (priority = DEF_PRIORITY; priority >= max_priority; priority--) {
 		sc.nr_mapped = read_page_state(nr_mapped);
 		sc.nr_scanned = 0;
 		sc.nr_reclaimed = 0;
@@ -1491,6 +1570,8 @@
 		if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
 			blk_congestion_wait(WRITE, HZ/10);
 	}
+	if (--sc.pass >= 0)
+		goto again;
 out:
 	for (i = 0; zones[i] != 0; i++) {
 		struct zone *zone = zones[i];
@@ -1500,6 +1581,7 @@
 
 		zone->prev_priority = zone->temp_priority;
 	}
+	scanner_stop();
 	return ret;
 }
 
@@ -1531,12 +1613,15 @@
 static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order)
 {
 	int to_free = nr_pages;
-	int all_zones_ok;
+	int all_zones_ok = 1;
 	int priority;
 	int i;
 	int total_scanned, total_reclaimed;
 	struct reclaim_state *reclaim_state = current->reclaim_state;
 	struct scan_control sc;
+	int max_priority;
+
+	scanner_start();
 
 loop_again:
 	total_scanned = 0;
@@ -1545,6 +1630,7 @@
 	sc.may_writepage = !laptop_mode;
 	sc.may_swap = 1;
 	sc.nr_mapped = read_page_state(nr_mapped);
+	sc.pass = (nr_pages == 0) ? !!mapped_bias : 0;
 
 	inc_page_state(pageoutrun);
 
@@ -1553,8 +1639,13 @@
 
 		zone->temp_priority = DEF_PRIORITY;
 	}
-
-	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
+again:
+	/*
+	 * Only scan down to 0 on the last pass.
+	 */
+	max_priority = (sc.pass == 0) ? 0 : 1;
+	
+	for (priority = DEF_PRIORITY; priority >= max_priority; priority--) {
 		int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
 		unsigned long lru_pages = 0;
 
@@ -1563,7 +1654,7 @@
 			disable_swap_token();
 
 		all_zones_ok = 1;
-
+	
 		if (nr_pages == 0) {
 			/*
 			 * Scan in the highmem->dma direction for the highest
@@ -1593,7 +1684,13 @@
 		for (i = 0; i <= end_zone; i++) {
 			struct zone *zone = pgdat->node_zones + i;
 
-			lru_pages += zone->nr_active + zone->nr_inactive;
+			/*
+			 * When mapped bias is in effect,
+			 * do not count active pages.
+			 */
+			lru_pages += zone->nr_inactive;
+			if (!mapped_bias)
+				lru_pages += zone->nr_active;
 		}
 
 		/*
@@ -1637,7 +1734,8 @@
 			if (zone->all_unreclaimable)
 				continue;
 			if (nr_slab == 0 && zone->pages_scanned >=
-				    (zone->nr_active + zone->nr_inactive) * 4)
+				    (zone->nr_active + zone->nr_inactive) * 4 *
+					(mapped_bias + 1))
 				zone->all_unreclaimable = 1;
 			/*
 			 * If we've done a decent amount of scanning and
@@ -1651,7 +1749,7 @@
 		if (nr_pages && to_free > total_reclaimed)
 			continue;	/* swsusp: need to do more work */
 		if (all_zones_ok)
-			break;		/* kswapd: all done */
+			goto out;	/* kswapd: all done */
 		/*
 		 * OK, kswapd is getting into trouble.  Take a nap, then take
 		 * another pass across the zones.
@@ -1666,8 +1764,10 @@
 		 * on zone->*_priority.
 		 */
 		if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages))
-			break;
+			goto out;
 	}
+	if (--sc.pass >= 0)
+		goto again;
 out:
 	for (i = 0; i < pgdat->nr_zones; i++) {
 		struct zone *zone = pgdat->node_zones + i;
@@ -1678,6 +1778,7 @@
 		cond_resched();
 		goto loop_again;
 	}
+	scanner_stop();
 
 	return total_reclaimed;
 }
@@ -1898,6 +1999,8 @@
 	if (!cpus_empty(mask) && node_id != numa_node_id())
 		return 0;
 
+	scanner_start();
+
 	sc.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE);
 	sc.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP);
 	sc.nr_scanned = 0;
@@ -1905,6 +2008,7 @@
 	sc.priority = ZONE_RECLAIM_PRIORITY + 1;
 	sc.nr_mapped = read_page_state(nr_mapped);
 	sc.gfp_mask = gfp_mask;
+	sc.pass = 0;
 
 	disable_swap_token();
 
@@ -1952,6 +2056,8 @@
 	if (sc.nr_reclaimed == 0)
 		zone->last_unsuccessful_zone_reclaim = jiffies;
 
+	scanner_stop();
+
 	return sc.nr_reclaimed >= nr_pages;
 }
 #endif

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Linda Walsh]

Charles Shannon Hendrix wrote:
> Mon, 27 Mar 2006 @ 19:59 -0800, Andrew Morton said:
>
>   
>> Much porkiness.
>>
>> /proc/meminfo is very useful for obtaining a top-level view of where all
>> the memory's gone to.  I'd tentatively say that your options are to put up
>> with the swapping or find a new mail client.
>>     
>
> I use mutt for my email, and I have the same issue on a 1GB system.
>
> I really wish we could put an upper limit on what file cache can use.
>   
----
    Hmmm, not to be contrary, but I have a 1GB system that refuses to swap
during large file i/o operations.  For the first time in a *long* time,
I read someone's suggestion to increase swappiness -- I did, to 75 or 80,
(I've booted since then, so it's back to 60 and no swap usage) and some of
the programs that rarely run actually swapped.  It was great!  I finally had
more memory for file i/o operations.

    Maybe you are telling the system to "feel free" to use swap by having a
large swap file?  I have a 256Mb swap partition near the front of the disk
where I/O is fastest, but it usually remains untouched, but that also means
I can only overcommit used memory by 25% (1Gphys, 256M swap).  I don't know
what the OOM "looks like" when it runs.  I had a buggy perlapp, once, that
tried to consume infinite memory, but I think it segfaulted before the OOM
could act.

    Maybe if you don't want linux to swap as much, it might swap less if 
you give
it less to swap with?  I know it sounds simplistic, but I've run with 
smallish
swap files ever since I got up to 1GB of main memory.  The only reason I 
have one
at all is I presumed that infrequently used functions, like dhcp (only 
used when
friends are over) would be shuffled out -- but it isn't unless I increase
swappiness.
> I shouldn't be suffering from swap storms.
>   
I agree.  Try getting rid of your swap file entirely -- your system will 
still
run unless you are overloading memory, but you have a Gig.  How much do you
need to keep in memory?  Sure, if/when I get a 4-way CPU (I have a 2-cpu 
setup now),
I might go up to 4G, but I might be running multiple virtual machines too!
> For example, my normal working set of programs eats about 250MB of memory. If
> I also start a job running to something like tag some mp3s, copy a CD, or just
> process a lot of files, it only takes a few minutes before performance becomes
> unacceptable.  
>   
---
    You might try the "cfq" block i/o algorithm.  Then you can
ionice down the disk priority of background processes (though you need
to be root to reduce ionice levels at this point, unlike cpu nice).
> If you are doing some work where you switch among several applications
> frequently, the pigginess of file cache becomes a serious problem.
>   
---
    Never a problem.  I don't allocate enough swap for it to be a 
problem I'm
guessing. Programs stay in memory and blocks get forced out to disk more
frequently.

Linda

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Charles Shannon Hendrix]

Wed, 05 Apr 2006 @ 16:47 -0400, Bill Davidsen said:

Sorry for the late reply, and if this is a duplicate.

> >I shouldn't be suffering from swap storms.
> 
> Agreed, does meminfo show that you are? 

meminfo?

procinfo and other tools show a lot swapping, if that's what you mean, and you
can see it in disk I/O to the swap drives as well.

> The reason I ask is that I have noted that large memory machines and CD/DVD
> image writing suffer from some interesting disk write patterns. The image
> being built gets cached but not written, then the file is closed. At some
> point the kernel notices several GB of old unwritten data and decides to
> write it. This makes everything pretty slow for a while, even if you have
> 100MB/s disk system.

I see that kind of behavior quite a lot. Not just for DVD/CD images either.
Basically any large data processing fills memory with cached file data at the
expense of other programs and data.

> In theory you should be able to tune this, but in practice I see what
> you do. On small memory machines it's less noticable, oddly.

I tried putting swapiness down to 30. It helped, most of the time, but still
I saw way too much useless file data being cached.

I would personally rather just limit how much file data can be cached. I don't
mind agressive swapping, I just hate seeing a ton of file data being cached
that isn't going to be used again.

I'm also trying the ck kernels just to see how they run. So far they work
better.

-- 
shannon "AT" widomaker.com -- ["All of us get lost in the darkness,
dreamers turn to look at the stars" -- Rush ]

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Charles Shannon Hendrix]

Tue, 11 Apr 2006 @ 01:33 -0700, Linda Walsh said:

>    Hmmm, not to be contrary, but I have a 1GB system that refuses to swap
> during large file i/o operations.  For the first time in a *long* time,
> I read someone's suggestion to increase swappiness -- I did, to 75 or 80,
> (I've booted since then, so it's back to 60 and no swap usage) and some of
> the programs that rarely run actually swapped.  It was great!  I finally had
> more memory for file i/o operations.

It's great if you actually need the file data that gets stored.

>    Maybe you are telling the system to "feel free" to use swap by having a
> large swap file?  

I don't believe that matters, and certainly doesn't seem to affect my
own system.

If I use a smaller swap file, I just run out faster.

Is your experience different?

> I agree.  Try getting rid of your swap file entirely -- your system
> will still run unless you are overloading memory, but you have a Gig.
> How much do you need to keep in memory?  Sure, if/when I get a 4-way
> CPU (I have a 2-cpu setup now), I might go up to 4G, but I might be
> running multiple virtual machines too!

Sure it will run, but I *want* swap to be used to remove unused
programs.

My current problem is that *useful* program code is being swapped out and
being replaced by *useless* cached file data.

>    You might try the "cfq" block i/o algorithm.  Then you can
> ionice down the disk priority of background processes (though you need
> to be root to reduce ionice levels at this point, unlike cpu nice).

I've not seen ionice.


-- 
shannon "AT" widomaker.com -- ["All of us get lost in the darkness,
dreamers turn to look at the stars" -- Rush ]

Re: OOM kills if swappiness set to 0, swap storms otherwise

[Randy.Dunlap]

On Tue, 2 May 2006 00:21:08 -0400 Charles Shannon Hendrix wrote:

> Tue, 11 Apr 2006 @ 01:33 -0700, Linda Walsh said:
> 
> >    Hmmm, not to be contrary, but I have a 1GB system that refuses to swap
> > during large file i/o operations.  For the first time in a *long* time,
> > I read someone's suggestion to increase swappiness -- I did, to 75 or 80,
> > (I've booted since then, so it's back to 60 and no swap usage) and some of
> > the programs that rarely run actually swapped.  It was great!  I finally had
> > more memory for file i/o operations.
> 
> It's great if you actually need the file data that gets stored.
> 
> >    Maybe you are telling the system to "feel free" to use swap by having a
> > large swap file?  
> 
> I don't believe that matters, and certainly doesn't seem to affect my
> own system.
> 
> If I use a smaller swap file, I just run out faster.
> 
> Is your experience different?
> 
> > I agree.  Try getting rid of your swap file entirely -- your system
> > will still run unless you are overloading memory, but you have a Gig.
> > How much do you need to keep in memory?  Sure, if/when I get a 4-way
> > CPU (I have a 2-cpu setup now), I might go up to 4G, but I might be
> > running multiple virtual machines too!
> 
> Sure it will run, but I *want* swap to be used to remove unused
> programs.
> 
> My current problem is that *useful* program code is being swapped out and
> being replaced by *useless* cached file data.
> 
> >    You might try the "cfq" block i/o algorithm.  Then you can
> > ionice down the disk priority of background processes (though you need
> > to be root to reduce ionice levels at this point, unlike cpu nice).
> 
> I've not seen ionice.

It's hidden^w embedded in Documentation/block/ioprio.txt ...

---
~Randy