RE: i686 SMP systems with more then 12 GB ram with 2.4.x kernel ?

[M. Edward Borasky]

Hmmm ... 0 order allocation failures ... is that new *after* my patch or
were you getting those before? Maybe we've *moved* the problem??

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> -----Original Message-----
> From: [e-mail]
> [mailto:[e-mail]]On Behalf Of Harald Holzer
> Sent: Saturday, December 29, 2001 6:15 PM
> To: M. Edward (Ed) Borasky; [e-mail]
> Subject: Re: i686 SMP systems with more then 12 GB ram with 2.4.x kernel
> ?
>
>
> I tested your suggestion with an 2.4.17rc2aa2 kernel,
> but it didnt help.
> The system dies after copying more then 6-8GB on data.
> Here are the last lines from /var/log/messages:
>
> Dec 30 01:47:32 localhost kernel: __alloc_pages: 0-order
> allocation failed (gfp=0x70/0)
> Dec 30 01:47:32 localhost kernel: __alloc_pages: 0-order
> allocation failed (gfp=0x70/0)
> Dec 30 01:47:32 localhost kernel: __alloc_pages: 0-order
> allocation failed (gfp=0x1f0/0)
> Dec 30 01:47:32 localhost kernel: __alloc_pages: 0-order
> allocation failed (gfp=0x70/0)
> Dec 30 01:47:32 localhost kernel: __alloc_pages: 0-order
> allocation failed (gfp=0xf0/0)
> Dec 30 01:47:32 localhost kernel: __alloc_pages: 0-order
> allocation failed (gfp=0x70/0)
> Dec 30 01:47:32 localhost last message repeated 3 times
> Dec 30 01:47:32 localhost kernel: __alloc_pages: 0-order
> allocation failed (gfp=0x1f0/0)
>
> I started to begin searching in the linux/fs/buffer.c, and found the
> following interesting lines (line: 1450+):
>
> void create_empty_buffers(struct page *page, kdev_t dev, unsigned
> long blocksize)
> {
> 	struct buffer_head *bh, *head, *tail;
>
> 	/* FIXME: create_buffers should fail if there's no enough memory */
> 	head = create_buffers(page, blocksize, 1);
> 	if (page->buffers)
> 		BUG();
>
> 	bh = head;
>
> Could the create_buffer function cause this problem ?
>
> Harald Holzer
>
> On Sun, 2001-12-30 at 01:25, M. Edward (Ed) Borasky wrote:
> > On Sat, 29 Dec 2001, M. Edward (Ed) Borasky wrote:
> >
> > > On Sat, 29 Dec 2001, Alan Cox wrote:
> > >
> > > > Because much of the memory cannot be used for kernel objects there
> > > > is an imbalance in available resources and its very hard to balance
> > > > them sanely.  I'm not sure how many 8Gb+ machines Andrea has handy
> > > > to tune the VM on either.
> > >
> > > Along those lines -- I have in front of me the source to
> > > "/linux/mm/page_alloc.c" (2.4.17 kernel) which reads (partially)
> >
> > [snip]
> >
> >
> > > Could someone with a big box and a benchmark that drives it out of
> > > free memory please try commenting out the "else if" clause and see if
> > > it makes a difference? I tried this on my puny 512 MB Athlon and
> > > verified that the right values were there with "sysrq", but I don't
> > > have anything bigger to try it on and I don't have a benchmark to test
> > > it with either.
> >
> > And here it is as a patch against 2.4.17:
> >
> > diff -ur linux/mm/page_alloc.c linux-2.4.17znmeb/mm/page_alloc.c
> > --- linux/mm/page_alloc.c	Mon Nov 19 16:35:40 2001
> > +++ linux-2.4.17znmeb/mm/page_alloc.c	Sat Dec 29 16:04:25 2001
> > @@ -718,8 +718,13 @@
> >  		mask = (realsize / zone_balance_ratio[j]);
> >  		if (mask < zone_balance_min[j])
> >  			mask = zone_balance_min[j];
> > +		/* else if clause commented out for testing
> > +		 * M. Edward Borasky, Borasky Research
> > +		 * 2001-12-29
> > +		 *
> >  		else if (mask > zone_balance_max[j])
> >  			mask = zone_balance_max[j];
> > +		 */
> >  		zone->pages_min = mask;
> >  		zone->pages_low = mask*2;
> >  		zone->pages_high = mask*3;
> >
> >
> > Apologies if pine with vim as the editor messes this puppy up :-).
> > --
> > M. Edward Borasky
> >
> > [e-mail]
> > http://www.borasky-research.net
> >
> > I brought my inner child to "Take Your Child To Work Day."
> >
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