lkml.org 
[lkml]   [2005]   [Jan]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH][5/?] count writeback pages in nr_scanned
Rik van Riel <riel@redhat.com> wrote:
>
> On Thu, 6 Jan 2005, Nick Piggin wrote:
>
> > I think what Andrea is worried about is that blk_congestion_wait is
> > fairly vague, and can be a source of instability in the scanning
> > implementation.
>
> The recent OOM kill problem has been happening:
> 1) with cache pressure on lowmem only, due to a block device write
> 2) with no block congestion at all
> 3) with pretty much all pageable lowmme pages in writeback state

You must have a wild number of requests configured in the queue. Is this
CFQ?

I've done testing with "all of memory under writeback" before and it went
OK. It's certainly a design objective to handle this well. But that
testing was before we broke it.

> It appears the VM has trouble dealing with the situation where
> there is no block congestion to wait on...

It's misnamed. We don't "wait for the queue to come out of congestion".
We simply throttle until a write completes, or, rarely, timeout.

The bug which you fixed would cause the VM to scan itself to death without
throttling. Did the fix fix things?
-
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 14:09    [W:0.121 / U:0.152 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site