Re: 0-order allocation problem

[Marcelo Tosatti <marcelo@conectiva.com.br>]

On Thu, 16 Aug 2001, Hugh Dickins wrote:

> On Wed, 15 Aug 2001, Marcelo Tosatti wrote:
> > 
> > Hugh, could you check which kind of allocation is failing and from where?
> > (allocation flags, etc).
> 
> Whenever I looked the allocation flags were 0x70,
> __GFP_IO|__GFP_HIGH|__GFP_WAIT; but presumably PF_MEMALLOC too.
> 
> What I was doing was running a memory hog (for 600MB with 256MB
> RAM and 512MB swap), exiting that, doing swapoff -a and swapon -a
> (being interested in timing different swapoff methods).  First
> run no problem at all, but when immediately run again after,
> collapsed into endless 0-order allocation failure messages.
> Didn't happen in 2.4.8.  Linus' patch to 2.4.9-pre4 gets it
> back to work again, after a burst of those messages.
> 
> The stack trace was usually some high-level function, _alloc_pages,
> __alloc_pages, try_to_free_pages, do_try_to_free_pages, page_launder,
> swap_writepage, rw_swap_page, rw_swap_page_base, brw_page,
> create_empty_buffers, create_buffers, get_unused_buffer_head,
> kmem_cache_alloc, kmem_cache_grow, __get_free_pages,
> _alloc_pages, __alloc_pages, printk.
> 
> But on one occasion it was kswapd calling
> do_try_to_free_pages, page_launder, swap_writepage... as above.

Linus, 

The problem is probably "showing up" due to the reduced scan of the
inactive dirty list in 2.4.9pre.

It looks like allocations keep failing until page_launder() finds clean
buffers to free. Since the scan rate is much smaller now, that is likely
to happen.

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