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Date: Tue, 24 Aug 2004 15:40:15 -0300
From: Marcelo Tosatti <marcelo.tosatti@cyclades.com>
To: Andrew Morton <akpm@osdl.org>
Cc: nickpiggin@yahoo.com.au, us15@os.inf.tu-dresden.de, torvalds@osdl.org,
       linux-kernel@vger.kernel.org
Subject: Re: Possible dcache BUG
Message-ID: <20040824184015.GD8806@logos.cnet>
References: <20040812180033.62b389db@laptop.delusion.de> <Pine.LNX.4.58.0408121813190.1839@ppc970.osdl.org> <20040820000238.55e22081@laptop.delusion.de> <20040820001154.0a5cf331.akpm@osdl.org> <20040820001905.27a9ff8f@laptop.delusion.de> <4125AD23.4000705@yahoo.com.au> <20040823230824.3c937d88@laptop.delusion.de> <412AF113.6000804@yahoo.com.au> <20040824182036.GB8806@logos.cnet> <20040824130027.77b7b0f9.akpm@osdl.org>
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On Tue, Aug 24, 2004 at 01:00:27PM -0700, Andrew Morton wrote:
> Marcelo Tosatti <marcelo.tosatti@cyclades.com> wrote:
> >
> > I dont fully understand the all_unreclaimable logic yet.
> 
> 1) bk revtool include/linux/mmzone.h
> 2) double-click on declaration of all_unreclaimable
> 3) read changelog ;)

Will do, but my question is still unanswered, why stop IO throttling when all_unreclaimable
is set? 

Doesnt make sense to me right now.

OK, will RTFS.

> 
> > --- mm/vmscan.c.orig	2004-08-24 16:48:09.467086840 -0300
> > +++ mm/vmscan.c	2004-08-24 16:51:55.304754296 -0300
> > @@ -878,7 +878,8 @@
> >  		if (zone->prev_priority > sc->priority)
> >  			zone->prev_priority = sc->priority;
> >  
> > -		if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY)
> > +		if (zone->all_unreclaimable && 
> > +				(sc->priority < DEF_PRIORITY && sc->priority > 0))
> >  			continue;	/* Let kswapd poll it */
> >  
> >  		shrink_zone(zone, sc);
> > @@ -1054,7 +1055,8 @@
> >  		for (i = 0; i <= end_zone; i++) {
> >  			struct zone *zone = pgdat->node_zones + i;
> >  
> > -			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
> > +			if (zone->all_unreclaimable && 
> > +					(priority < DEF_PRIORITY && priority > 0))
> >  				continue;
> >  
> >  			if (nr_pages == 0) {	/* Not software suspend */
> 
> Does anyone understand _why_ all_unreclaimable is getting set?
> 
> If not, it's too early to be writing patches...

As I wrote down in the first email, kswapd does

                        if (zone->pages_scanned > zone->present_pages * 2)
                                zone->all_unreclaimable = 1;

Sure, it makes perfect sense to happen when we can't unreclaim pages
from the zone.

Its not something hard to understand. What is your point?

I suppose your question is not "_why_ all_unreclaimable is getting set?" but 
"maybe it should not be getting set?". 

Anyway, will RTFS.