2.4 todo list update

2.4 todo list update

[Rik van Riel]

Hi Ted,

in the last few weeks quite a few of the bugs listed on your
(excellent) http://linux24.sourceforge.net/ have been fixed.

Here is a list of the VM bugs that are on your list and can
be moved to the "fixed" category:

* truncate->invalidate_inode_pages removes mapping information from
  mapped pages which may be dirty; sync_pte -> crash. (CRITICAL)

	fixed by Linus and Al

* VM: raw I/O data loss (raw IO may arrive in a page which afer it
  is unammped from a process) (CRITICAL)

	fixed by Linus, now page_launder() does the IO
	and try_to_swap_out() only unmaps the pte
 
* VM: Fix the highmem deadlock, where the swapper cannot create low
  memory bounce buffers OR swap out low memory because it has
  consumed all resources {CRITICAL}

	this was never an issue, the pagecache has been
	highmem safe for a long time and the whole bounce
	buffer creation has been removed

* VM: page->mapping->flush() callback in page_lauder() for easier
  integration with journaling filesystem and maybe the network
  filesystems 

	page->mapping->writepage(), used from page_launder()
	... now ext3, reiserfs, xfs and others need to make
	their own ->writepage() function
	... some semantics are still being discussed, but it's
	mostly ready

* VM: maybe rebalance the swapper a bit... we do page aging now so
  maybe refill_inactive_scan() / shm_swap() and swap_out() need to
  be rebalanced a bit

	moving shm into the page cache permanently and doing
	the page down aging from refill_inactive_scan() seems
	to have fixed most of this
	... low priority, but may still have some room for
	improvement  (consider it fixed)



The following bugs _could_ be fixed ... I'm not 100% certain
but they're probably gone (could somebody confirm/deny?):

* mm->rss is modified in some places without holding the
  page_table_lock

* VFS?VM - mmap/write deadlock (demo code seems to show lock
  is there)


The "probably post 2.4" category VM issues remain ... maybe
we want to add the following 2 items though:

* VM: experiment with different forms of page aging ... maybe
  different aging rates for pages of different ages

* VM: RSS ulimit enforcement (trivial)


regards,

Rik
--
Virtual memory is like a game you can't win;
However, without VM there's truly nothing to loose...

		http://www.surriel.com/
http://www.conectiva.com/	http://distro.conectiva.com.br/

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Re: 2.4 todo list update

[Alan Cox]

> * VFS?VM - mmap/write deadlock (demo code seems to show lock
>   is there)

Linus fixed that.
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Re: 2.4 todo list update

[Matti Aarnio]

On Fri, Jan 05, 2001 at 12:58:34PM -0200, Rik van Riel wrote:
> Hi Ted,
> 
> in the last few weeks quite a few of the bugs listed on your
> (excellent) http://linux24.sourceforge.net/ have been fixed.

Adding to Rik's items, other things I spot at that "old" list
having changed over last 6 weeks, or so:

o Various Alpha's don't boot under 2.4.0-test9 (PCI-PCI bridge init issues)
o Alpha SMP problem: RSN reuse

	I assume that latter is typo and in reality ASN reuse.
	Fixes got merged during the preprelease-diffs

o Restore O_SYNC functionality ...
o Forwawrd port 2.2 fixes to allow 2 GHz or faster CPU's. {CRITICAL} 

	Also folded in during prerelease-diffs


o mtrr.c is broken for machines with >= 4GB of memory (David Wragg has a fix)

	Merged in at test12 or test13, I think.

o devfs and NFS problems

	fixes are also aplenty over last 6 weeks.

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Re: 2.4 todo list update

[Eric W. Biederman]

Rik van Riel <riel@conectiva.com.br> writes:


> The following bugs _could_ be fixed ... I'm not 100% certain
> but they're probably gone (could somebody confirm/deny?):
> 
> * mm->rss is modified in some places without holding the
>   page_table_lock

As of linux-2.4.0-test13-pre7 I can confirm that this bug
still exists.  The most obvious  location is in zap_page_range,
there may be others as well.

Eric

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Re: 2.4 todo list update

[Rik van Riel]

On 7 Jan 2001, Eric W. Biederman wrote:
> Rik van Riel <riel@conectiva.com.br> writes:
> 
> > The following bugs _could_ be fixed ... I'm not 100% certain
> > but they're probably gone (could somebody confirm/deny?):
> > 
> > * mm->rss is modified in some places without holding the
> >   page_table_lock
> 
> As of linux-2.4.0-test13-pre7 I can confirm that this bug still
> exists.  The most obvious location is in zap_page_range, there
> may be others as well.

Hmm, this is something we really want to check in 2.4.0.
Not a showstopper, but something we want to check anyway ;)

regards,

Rik
--
Virtual memory is like a game you can't win;
However, without VM there's truly nothing to loose...

		http://www.surriel.com/
http://www.conectiva.com/	http://distro.conectiva.com.br/

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