lkml.org 
[lkml]   [2001]   [Oct]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: new OOM heuristic failure (was: Re: VM: qsbench)
On Wed, 31 Oct 2001 14:04:45 -0200 (BRST) Rik van Riel <riel@conectiva.com.br>
wrote:

> On Wed, 31 Oct 2001, Linus Torvalds wrote:
>
> > I could probably argue that the machine really _is_ out of memory at this
> > point: no swap, and it obviously has to work very hard to free any pages.
> > Read the "out_of_memory()" code (which is _really_ simple), with the
> > realization that it only gets called when "try_to_free_pages()" fails and
> > I think you'll agree.
>
> Absolutely agreed, an earlier out_of_memory() is probably a good
> thing for most systems. The only "but" is that Lorenzo's test
> program runs fine with other kernels, but you could argue that
> it's a corner case anyway...

I took a deep look into this code and wonder how this benchmark manages to get
killed. If I read that right this would imply that shrink_cache has run a
hundred times through the _complete_ inactive_list finding no free-able pages,
with one exception that I read across:

int max_mapped = nr_pages*10;
...
page_mapped:
if (--max_mapped >= 0)
continue;

/*
* Alert! We've found too many mapped pages on the
* inactive list, so we start swapping out now!
*/
spin_unlock(&pagemap_lru_lock);
swap_out(priority, gfp_mask, classzone);
return nr_pages;

Is it possible, that this does a too early exit from shrink_cache?
I don't know how much mem Lorenzo has, but running only once through several
hundred MB of inactive list is a notable time in my system, running a hundred
times through could be far more than 70 s. But if there's no complete run, you
cannot state to really be oom.
Does it make sense to stop shrink_cache when having detected 4k * 32 * 10 =
1280 k of mapped mem on the inactive list of possibly several hundred MB in
size?

Regards,
Stephan

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:12    [W:0.101 / U:0.384 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site