Re: Andrea VM changes

[Marcelo Tosatti <marcelo@parcelfarce.linux.theplanet.co.uk>]

---------- Forwarded message ----------
Date: Sun, 31 Aug 2003 14:14:06 -0300 (BRT)
From: Marcelo Tosatti <marcelo@parcelfarce.linux.theplanet.co.uk>
To: Andrea Arcangeli <andrea@suse.de>
Cc: Marcelo Tosatti <marcelo@conectiva.com.br>,
     Mike Fedyk <mfedyk@matchmail.com>, Antonio Vargas <wind@cocodriloo.com>,
     lkml <linux-kernel@vger.kernel.org>,
     Marc-Christian Petersen <m.c.p@wolk-project.de>
Subject: Re: Andrea VM changes



On Sat, 30 Aug 2003, Andrea Arcangeli wrote:

> On Sat, Aug 30, 2003 at 12:13:57PM -0300, Marcelo Tosatti wrote:
> > 
> > > You need to integrate with -aa on the VM.  It has been hard enough for
> > > Andrea to get his stuff in, I doubt you will fair any better.
> > 
> > Thats because I never received separate patches which make sense one by
> > one.  Most of Andreas changes are all grouped into few big patches that
> > only he knows the mess. That is not the way to merge things.
> > 
> > I want to work out with him after I merge other stuff to address that.
> 
> that's true for only one patch, the others are pretty orthogonal after
> Andrew helped splitting them:
> 
> 
> 05_vm_03_vm_tunables-4
> 05_vm_05_zone_accounting-2
> 05_vm_06_swap_out-3

Help me understand something about this patch. In try_to_free_pages(), you
set failed_swapout to zero in case we are under __GFP_IO. And
failed_swapout decides whether we swap_out() or not.

So basically with -aa swap_out() is only called by __GFP_IO tasks (which
are throttled by the page laundering code in shrink_cache) and in mainline
non __GFP_IO tasks do swap_out() (and those are not throttled by anything).

Did I understood this right? 

Part 2:

Now in try_to_free_pages_zone() and shrink_cache you have: 

    if (!*failed_swapout)
        *failed_swapout =  !swap_out(classzone);

Which means: Keep trying to swap_out() only in case swap_out()  
successfully desactivates nr_pages pte's. Right? Do you do that to avoid
terrible expensive swap_out() loops which dont successfully free pages?

Thanks