1gb RAM + 1gb SWAP + make -j bzImage = OOM

1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Phil Oester]

On 2.4.17, I can't make -j bzImage without OOM kicking in.  Relatively
light .config here - bzImage compiles to less than 1mb.

Seems with 1 gb of RAM and swap, the box should be able to handle this
(box is dual P3 600 btw).  

Is this unreasonable?  How much RAM should it take to accomplish this???

-Phil Oester

Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Stephan von Krawczynski]

On Fri, 4 Jan 2002 12:32:27 -0800
"Phil Oester" <kernel@theoesters.com> wrote:

> On 2.4.17, I can't make -j bzImage without OOM kicking in.  Relatively
> light .config here - bzImage compiles to less than 1mb.
> 
> Seems with 1 gb of RAM and swap, the box should be able to handle this
> (box is dual P3 600 btw).  
> 
> Is this unreasonable?  How much RAM should it take to accomplish this???

You should give a bit more info on that, especially vmstat and the like.
I cannot reproduce this. Neither on 1GB/256MB nor on 2GB/256MB RAM/SWAP.
(P3-1GHz, dual SMP, 2.4.17)

Regards,
Stephan

Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Nicholas Knight]

On Friday 04 January 2002 01:02 pm, Stephan von Krawczynski wrote:
> On Fri, 4 Jan 2002 12:32:27 -0800
>
> "Phil Oester" <kernel@theoesters.com> wrote:
> > On 2.4.17, I can't make -j bzImage without OOM kicking in. 
> > Relatively light .config here - bzImage compiles to less than 1mb.
> >
> > Seems with 1 gb of RAM and swap, the box should be able to handle
> > this (box is dual P3 600 btw).
> >
> > Is this unreasonable?  How much RAM should it take to accomplish
> > this???
>
> You should give a bit more info on that, especially vmstat and the
> like. I cannot reproduce this. Neither on 1GB/256MB nor on 2GB/256MB
> RAM/SWAP. (P3-1GHz, dual SMP, 2.4.17)
>


I have absilutely no trouble reproducing on an 800MHz Athlon with 256MB 
RAM/256MB swap on 2.4.17

The one catch is that -j is specified without a number.

from man make:
       -j jobs
            Specifies  the  number  of  jobs  (commands) to run 
simultaneously.  If there is more than one -j
            option, the last one is effective.
**If the -j option is given without an argument, make will not limit 
the number of jobs that can run simultaneously.**

(emphasis mine)

Hence, unlimited number of jobs, theoreticaly unlimited amount of 
memory usage.
The last number of processes I saw in top before the system was 
basically dead and I just hit A-SYSRQ-S and A-SYSRQ-B was 416, and all 
the top processes were make or cc

Somehow I doubt this is a kernel issue and is instead a make and user 
issue. A make issue because it's probably poor design to have an option 
that's specified with a number be normaly harmless and useful, be 
potentialy lethal when the number is left off, so if you forget the 
number, your system is dead. A user issue because it seems the user is 
using the option without fully comprehending the consequences.

> Regards,
> Stephan
>

Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Phil Oester]

On Fri, Jan 04, 2002 at 04:42:43PM -0800, Nicholas Knight wrote:
> The one catch is that -j is specified without a number.

[snip superfluous description of what 'make -j' implies]

> number, your system is dead. A user issue because it seems the user is 
> using the option without fully comprehending the consequences.

eh?  Trust me - i understand the implications of make -j.  It's not an unreasonable test, especially on a machine with 1gb ram/swap.  For reference, read Rik's email regarding his reverse VM patch:

http://marc.theaimsgroup.com/?l=linux-kernel&m=101007711817127&w=2

Might be enlightening

-Phil

Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Luigi Genoni]

No troubles to reproduce this here, on sparc64 !GM ran/1GB swap,
and on dualathlon 768MB RAM 1.5GB swap, and on athlon 1GBRAM/1GBSWAP

But this is not a kernel issue, it is simply that
too many gcc processes are runned at the same time because the source
files are too many.

On Fri, 4 Jan 2002, Nicholas Knight wrote:

> On Friday 04 January 2002 01:02 pm, Stephan von Krawczynski wrote:
> > On Fri, 4 Jan 2002 12:32:27 -0800
> >
> > "Phil Oester" <kernel@theoesters.com> wrote:
> > > On 2.4.17, I can't make -j bzImage without OOM kicking in.
> > > Relatively light .config here - bzImage compiles to less than 1mb.
> > >
> > > Seems with 1 gb of RAM and swap, the box should be able to handle
> > > this (box is dual P3 600 btw).
> > >
> > > Is this unreasonable?  How much RAM should it take to accomplish
> > > this???
> >
> > You should give a bit more info on that, especially vmstat and the
> > like. I cannot reproduce this. Neither on 1GB/256MB nor on 2GB/256MB
> > RAM/SWAP. (P3-1GHz, dual SMP, 2.4.17)
> >
>
>
> I have absilutely no trouble reproducing on an 800MHz Athlon with 256MB
> RAM/256MB swap on 2.4.17
>
> The one catch is that -j is specified without a number.
>
> from man make:
>        -j jobs
>             Specifies  the  number  of  jobs  (commands) to run
> simultaneously.  If there is more than one -j
>             option, the last one is effective.
> **If the -j option is given without an argument, make will not limit
> the number of jobs that can run simultaneously.**
>
> (emphasis mine)
>
> Hence, unlimited number of jobs, theoreticaly unlimited amount of
> memory usage.
> The last number of processes I saw in top before the system was
> basically dead and I just hit A-SYSRQ-S and A-SYSRQ-B was 416, and all
> the top processes were make or cc
>
> Somehow I doubt this is a kernel issue and is instead a make and user
> issue. A make issue because it's probably poor design to have an option
> that's specified with a number be normaly harmless and useful, be
> potentialy lethal when the number is left off, so if you forget the
> number, your system is dead. A user issue because it seems the user is
> using the option without fully comprehending the consequences.
>
> > Regards,
> > Stephan
> >
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Stephan von Krawczynski]

[-- Attachment #1: Type: text/plain, Size: 1036 bytes --]

On Fri, 4 Jan 2002 17:24:18 -0800
Phil Oester <kernel@theoesters.com> wrote:

> On Fri, Jan 04, 2002 at 04:42:43PM -0800, Nicholas Knight wrote:
> > The one catch is that -j is specified without a number.
> 
> [snip superfluous description of what 'make -j' implies]
> 
> > number, your system is dead. A user issue because it seems the user is 
> > using the option without fully comprehending the consequences.
> 
> eh?  Trust me - i understand the implications of make -j.  It's not an
unreasonable test, especially on a machine with 1gb ram/swap.  For reference,
read Rik's email regarding his reverse VM patch:> 
> http://marc.theaimsgroup.com/?l=linux-kernel&m=101007711817127&w=2
> 
> Might be enlightening

I guess this testcase is somewhat driving in the direction of Martins test with
some setis running, meaning it has a lot of standard processes that need files
and try to work out something. Can you try Martins patch at your side, redo the
-j story and give us a result? I attached it for an easy go :-)

Thanks,
Stephan


[-- Attachment #2: vmscan.patch.2.4.17.c --]
[-- Type: text/plain, Size: 1275 bytes --]

--- linux.virgin/mm/vmscan.c	Mon Dec 31 12:46:25 2001
+++ linux/mm/vmscan.c	Thu Jan  3 19:43:02 2002
@@ -394,9 +394,9 @@
 		if (PageDirty(page) && is_page_cache_freeable(page) && page->mapping) {
 			/*
 			 * It is not critical here to write it only if
-			 * the page is unmapped beause any direct writer
+			 * the page is unmapped because any direct writer
 			 * like O_DIRECT would set the PG_dirty bitflag
-			 * on the phisical page after having successfully
+			 * on the physical page after having successfully
 			 * pinned it and after the I/O to the page is finished,
 			 * so the direct writes to the page cannot get lost.
 			 */
@@ -480,11 +480,14 @@
 
 			/*
 			 * Alert! We've found too many mapped pages on the
-			 * inactive list, so we start swapping out now!
+			 * inactive list.
+			 * Move referenced pages to the active list.
 			 */
-			spin_unlock(&pagemap_lru_lock);
-			swap_out(priority, gfp_mask, classzone);
-			return nr_pages;
+			if (PageReferenced(page)) {
+				del_page_from_inactive_list(page);
+				add_page_to_active_list(page);
+			}
+			continue;
 		}
 
 		/*
@@ -521,6 +524,9 @@
 	}
 	spin_unlock(&pagemap_lru_lock);
 
+	if (max_mapped <= 0 && nr_pages > 0)
+		swap_out(priority, gfp_mask, classzone);
+
 	return nr_pages;
 }
 

Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Stephan von Krawczynski]

On Fri, 4 Jan 2002 16:42:43 -0800
Nicholas Knight <nknight@pocketinet.com> wrote:


> I have absilutely no trouble reproducing on an 800MHz Athlon with 256MB 
> RAM/256MB swap on 2.4.17

The simple question is: is the RAM sufficient at all to spawn such a lot of cc
processes? In my setup I get around 1000 concurrently working during -j. This
sounds like a real problem for 256/256, or not?

Regards,
Stephan

Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Nicholas Knight]

On Saturday 05 January 2002 07:19 am, Stephan von Krawczynski wrote:
> On Fri, 4 Jan 2002 16:42:43 -0800
>
> Nicholas Knight <nknight@pocketinet.com> wrote:
> > I have absilutely no trouble reproducing on an 800MHz Athlon with
> > 256MB RAM/256MB swap on 2.4.17
>
> The simple question is: is the RAM sufficient at all to spawn such a
> lot of cc processes? In my setup I get around 1000 concurrently
> working during -j. This sounds like a real problem for 256/256, or
> not?

Matter of scale, did you try a full kernel build with make -j bzImage 
using whatever your normal config is?
I still believe this is an innappropriate test, sure if you have tons 
of RAM and swap it may eventualy complete (though if the swapfile is 
very active and this is tried on a 2.4 kernel, the amount of CPU time 
the compile will actually get will likely be unpredictable at best.) 
This is an option that does nothing less than flood the system with 
hundreds or thousands of processes that on any large compile will 
simply not allow the system to survive intact without killing all the 
processes. Does the OOM killer even work correctly yet? Or does it 
still try to kill init at times? And for that matter, what order does 
it kill in?

>
> Regards,
> Stephan

Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Eric W. Biederman]

Phil Oester <kernel@theoesters.com> writes:

> On Fri, Jan 04, 2002 at 04:42:43PM -0800, Nicholas Knight wrote:
> > The one catch is that -j is specified without a number.
> 
> [snip superfluous description of what 'make -j' implies]
> 
> > number, your system is dead. A user issue because it seems the user is 
> > using the option without fully comprehending the consequences.
> 
> eh?  Trust me - i understand the implications of make -j.  It's not an
> unreasonable test, especially on a machine with 1gb ram/swap.  For reference,
> read Rik's email regarding his reverse VM patch:
> 
> 
> http://marc.theaimsgroup.com/?l=linux-kernel&m=101007711817127&w=2
> 
> Might be enlightening

Yes.  It sounds like he Rick slowed down fork enough the system didn't fall
over.  There may be some other policy changes as well.  But my hunch is that
it is a fork speed thing.  If all that happens is that the system hits
OOM when subjected to an unreasonable load I don't see this as a problem.

The truly interesting question is what happens when you and more swap.
With sufficient swap will it work?

Eric

Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Stephan von Krawczynski]

On Sat, 5 Jan 2002 09:57:17 -0800
Nicholas Knight <nknight@pocketinet.com> wrote:

> On Saturday 05 January 2002 07:19 am, Stephan von Krawczynski wrote:
> > On Fri, 4 Jan 2002 16:42:43 -0800
> >
> > Nicholas Knight <nknight@pocketinet.com> wrote:
> > > I have absilutely no trouble reproducing on an 800MHz Athlon with
> > > 256MB RAM/256MB swap on 2.4.17
> >
> > The simple question is: is the RAM sufficient at all to spawn such a
> > lot of cc processes? In my setup I get around 1000 concurrently
> > working during -j. This sounds like a real problem for 256/256, or
> > not?
> 
> Matter of scale, did you try a full kernel build with make -j bzImage 
> using whatever your normal config is?

Yes, of course, and it works at my side. Worked with 1GB RAM/256MB swap, works
now with 2GB RAM/256MB swap on stock 2.4.17.

> I still believe this is an innappropriate test, sure if you have tons 
> of RAM and swap it may eventualy complete

I never saw it not completing on my box with 2.4.17, regardless of what I do in
the mean time (writing mails or the like). Of course system performance drops
somehow down when load reaches about 150, but I think this can be expected ;-)

Regards,
Stephan

RE: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Phil Oester]

I've rerun this test a number of times, and cannot reliably reproduce
the OOM - though it still does OOM occasionally.  It never OOM's right
after a bootup - usually the greatest chance of OOM is after 2 or 3
consecutive runs without a reboot.  Once it even froze the box and
required a powercycle.

I'm surprised you cannot OOM with 1gb RAM/256MB swap, as sometimes I'm
over 900MB in swap - did you try consecutive runs, or just once and then
reboot between each run?

On a side note, there seems to be some debate as to whether this is a
valid test.  The detractors primarily claim that 'make -j' just
overloads the machine with too many processes and therefore is setting
it up to fail.  My position has always been that the kernel
_should_not_OOM_ under this test due to the ~2gb of ~RAM being thrown at
it.  It may die for any number of other reasons, but OOM shouldn't be
one of them.  In other words, either the OOM killer may be too
aggressive here, or the kernel isn't reclaiming inactive RAM under heavy
load.

Haven't yet tried Martin's patch - though since I can't reliably produce
the OOM, testing it wouldn't help much.

-Phil Oester


-----Original Message-----
From: Stephan von Krawczynski [mailto:skraw@ithnet.com] 
Sent: Saturday, January 05, 2002 7:17 AM
To: Phil Oester
Cc: nknight@pocketinet.com; linux-kernel@vger.kernel.org
Subject: Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

I guess this testcase is somewhat driving in the direction of Martins
test with
some setis running, meaning it has a lot of standard processes that need
files
and try to work out something. Can you try Martins patch at your side,
redo the
-j story and give us a result? I attached it for an easy go :-)

Thanks,
Stephan

Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Stephan von Krawczynski]

On Sun, 6 Jan 2002 22:22:16 -0800
"Phil Oester" <kernel@theoesters.com> wrote:

> I've rerun this test a number of times, and cannot reliably reproduce
> the OOM - though it still does OOM occasionally.  It never OOM's right
> after a bootup - usually the greatest chance of OOM is after 2 or 3
> consecutive runs without a reboot.  Once it even froze the box and
> required a powercycle.
> 
> I'm surprised you cannot OOM with 1gb RAM/256MB swap, as sometimes I'm
> over 900MB in swap - did you try consecutive runs, or just once and then
> reboot between each run?

I tried just about everything I could think of and it never went in OOM. Even
the first test I did were with several days uptime - meaning far away from
"cleaning" reboot. I hate reboot :-)

> [...]
> Haven't yet tried Martin's patch - though since I can't reliably produce
> the OOM, testing it wouldn't help much.

Well, take the other side: if you do not manage to OOM afterwards, even at the
tenth consecutive try, there is probably something about the patch ...

Regards,
Stephan

RE: 1gb RAM + 1gb SWAP + make -j bzImage = OOM

[Phil Oester]

The vmscan patch doesn't seem to help in the 'make -j' testcase.  

Here's time of a couple runs:

2.4.17 vanilla

real    32m2.097s
user    9m51.800s
sys     3m47.700s

real    19m45.696s
user    9m55.820s
sys     2m32.170s

2.4.17 + vmscan patch

gave up waiting after 2 hours...never finished.

Unfortunately, box was not responsive enough to gather any useful
information.  Perhaps not swapping enough???

-Phil

-----Original Message-----
From: Stephan von Krawczynski [mailto:skraw@ithnet.com] 
Sent: Monday, January 07, 2002 6:24 AM
To: Phil Oester
Cc: nknight@pocketinet.com; linux-kernel@vger.kernel.org
Subject: Re: 1gb RAM + 1gb SWAP + make -j bzImage = OOM


On Sun, 6 Jan 2002 22:22:16 -0800
"Phil Oester" <kernel@theoesters.com> wrote:

> I've rerun this test a number of times, and cannot reliably reproduce
> the OOM - though it still does OOM occasionally.  It never OOM's right
> after a bootup - usually the greatest chance of OOM is after 2 or 3
> consecutive runs without a reboot.  Once it even froze the box and
> required a powercycle.
> 
> I'm surprised you cannot OOM with 1gb RAM/256MB swap, as sometimes I'm
> over 900MB in swap - did you try consecutive runs, or just once and
then
> reboot between each run?

I tried just about everything I could think of and it never went in OOM.
Even
the first test I did were with several days uptime - meaning far away
from
"cleaning" reboot. I hate reboot :-)

> [...]
> Haven't yet tried Martin's patch - though since I can't reliably
produce
> the OOM, testing it wouldn't help much.

Well, take the other side: if you do not manage to OOM afterwards, even
at the
tenth consecutive try, there is probably something about the patch ...

Regards,
Stephan